JP2019149756A - Array antenna and wireless communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wireless communication system capable of improving the transmission rate per frequency with a simpler configuration. The same array antenna is used as a transmitting antenna and a receiving antenna. This array antenna includes a plurality of circular loop antennas arranged concentrically so that they share a center point. Each circular loop antenna has a perimeter equal to an integral multiple of the wavelength of the communication frequency. Each circular loop antenna has two feeds. In each of the circular loop antennas, the angle between the two power feeding units viewed from the center point is determined so that the phases of the signals input to the two power feeding units are orthogonal to each other at the communication frequency. [Selection diagram] Figure 3A

Description

  The present invention relates to an array antenna and a radio communication system, and more particularly to an array antenna and a radio communication system that can be suitably used for OAM (Orbital Angular Momentum) multiplex radio communication.

  In recent years, with the abundance of Internet content, the ultra-high-speed network using optical lines, and the spread of wireless networks to end users, individuals who are “anytime, anywhere, with anyone”, or “only now, only here, only you” Progress toward an advanced information society that enables the provision of information tailored to the needs of the world is progressing rapidly. Furthermore, the collection of big data by communication without using a sensor network is also progressing in parallel. Wireless systems that support these include mobile phones, Wimax (Worldwide Interoperability for Microwave Access), wireless LAN (Local Area Network), Bluetooth (registered trademark), UWB (Ultra Wide Band), and other systems provided by ZigBee. .

  In addition, services that connect these systems seamlessly and provide a combination of these systems are also progressing. These wireless systems occupy a specific communication band and perform communication. In particular, in order to transmit a large amount of data at high speed, it is necessary to use a wide frequency band, and frequency resources that are valuable resources are used. There was a problem of requiring many. For this reason, the importance of a technique capable of improving the transmission rate (bit / Hz) per frequency obtained by dividing the transmission information amount by the bandwidth as an index of effective use is increasing.

  As one of techniques that can improve the transmission rate per frequency, a technique called “line-of-sight MIMO (multiple-input and multiple-output)” in which a plurality of antennas are arranged on the transmission side and the reception side is known. . Line-of-sight MIMO is a method of spatial multiplexing that multiplexes within the same band within the same time using the difference in propagation characteristics. For example, when each of the transmission side and the reception side includes n antennas (n is an arbitrary integer), the relationship between the voltage current of the transmission antenna and the voltage current of the reception antenna is a transfer function (for example, Z matrix) of the propagation path. ) And is expressed as a square matrix of n rows × n columns.

  When the eigenvectors of this matrix are used, an n-row × n-column square matrix can be diagonalized, and transfer functions relating to n eigenvectors are independent, so that n-fold multiplexing is possible. However, in MIMO, there is a problem that complicated signal processing is required to mathematically separate mixed signals. In addition, since a plurality of antennas are operated in cooperation, there is a problem that the system configuration becomes complicated.

  Based on such a situation, recently, OAM (Orbital Angular Momentum) communication has been proposed as a multiplexing method at the same frequency. This technique utilizes a phenomenon in which the interaction is allowed only when the orbital angular momentum of the electromagnetic field is preserved, and is a technique for transmitting the electromagnetic wave with orbital angular momentum (OAM) information. .

  In a wave having a Gaussian distribution system such as a laser beam, the phase space distribution with respect to the direction φ in the cross section is constant for a normal wave. On the other hand, in the OAM wave, according to exp (jmφ) (where m is a mode order of the OAM wave and is called a magnetic quantum number), the OAM wave changes linearly with respect to the azimuth φ, and the same phase plane advances spirally.

  In the case of optical communication, such an OAM wave can be realized relatively easily using a laser and a hologram or a spiral phase plate. On the other hand, in the case of the microwave, since the transmission method and reception method of the eigenmode and the transmission method of the focused beam are greatly different from the optical communication, it is not easy to realize the OAM wave.

  In relation to the above, Patent Document 1 (WO 2014/199451) discloses a structure in the case of performing OAM communication with light, makes a parabolic antenna a spiral cut, and sets the reflecting surface to an integer of the wavelength. A technique for generating an OAM wave with electromagnetic waves by doubling is described.

  Further, in Patent Document 2 (Japanese Patent Laid-Open No. 2015-231108), arrayed antenna elements are arranged on the circumference, and the phases between the antenna elements are shifted at regular intervals, so that A technique for generating an electromagnetic field whose phase plane changes to exp (jmφ) at the reception position is described. In this technique, different OAM modes are created by discretely changing the phase amount to be shifted, and multiplexing is performed between the modes.

WO2014 / 199451 publication JP 2015-231108 A

  As described in Patent Document 1, an OAM wave can be generated by making a spiral cut in a parabolic antenna and shifting the reflecting surface by an integral multiple of the wavelength. However, it is not easy to manufacture a parabolic antenna having a special shape with cuts, and there is a problem that mass production is difficult.

  Further, as described in Patent Document 2, when the arrayed antenna elements are arranged on the circumference, as in the case of general MIMO communication, from the correlation between the received signals between the antennas. , Complicated signal processing is required to extract signals in each mode. Furthermore, on the transmission side, in order to create an electromagnetic field that rotates with exp (jmφ), it is necessary to arrange a phase shifter for giving a constant phase difference between the antennas. Therefore, when the arrayed antenna elements are arranged on the circumference, there is a problem that the configuration of the transmission circuit and the reception circuit becomes complicated.

  As described above, conventionally proposed techniques for improving the transmission rate per frequency have a problem that a complicated antenna is required and a transmission / reception circuit having a complicated configuration is required. It has been desired to improve the rate with a simpler configuration.

  Provided are an array antenna and a radio communication system capable of improving a transmission rate per frequency with a simpler configuration. Other problems and novel features will become apparent from the description of the specification and the accompanying drawings.

  The means for solving the problem will be described below using the numbers used in the (DETAILED DESCRIPTION). These numbers are added to clarify the correspondence between the description of (Claims) and (Mode for Carrying Out the Invention). However, these numbers should not be used to interpret the technical scope of the invention described in (Claims).

According to one embodiment, the array antenna (10) includes a dielectric substrate (13) and a plurality of circular loop antennas (12). Here, the dielectric substrate (13) has an upper surface that is one surface and a lower surface that is the other surface opposite to the upper surface. The plurality of circular loop antennas (12) are formed on the upper and lower surfaces of the dielectric substrate (13), and are concentrically arranged so as to share the center point (O). Each of the i-th circular loop antennas included in the plurality of circular loop antennas (12) has a different radius a _i . Here, the order of the symbol i is the same order as the magnitude relationship of the radius a _i . Perimeter 2Paiei _i, each having the i-th circular loop antenna is m _i times the wavelength λ corresponding to the communication frequency. Here m _i is a natural number, and magnitude of a natural number m _i is the same order as the sign _i. Each of the circular loop antennas (12A to 12D) includes an upper surface pattern (14A to 14D), a lower surface pattern (15A to 15D), a first power feeding unit (21), and a second power feeding unit (22). . Here, the upper surface patterns (14A to 14D) are arranged on the upper surface of the dielectric substrate (13). The lower surface patterns (15A to 15D) are arranged on the lower surface of the dielectric substrate (13). The first power feeding section (21) includes a first electrode (19) provided at one end of the upper surface pattern (14A to 14D) and a second electrode (20) provided at one end of the lower surface pattern (15A to 15D). including. The second power feeding unit (22) includes a third electrode (19) provided at the other end of the upper surface pattern (14A to 14D) and a fourth electrode (20 provided at the other end of the lower surface pattern (15A to 15D). ). n is an arbitrary integer, and in each of the i-th circular loop antennas (12A to 12D), a first radius passing through the center point (O) and the first feeding part (21), and the center point (O) and the first point the angle between the second radius passing through the second feeding part (22) is equal to (2n + 1) π / 2m i.

According to one embodiment, the wireless communication system (1) includes a transmitter (2), a first array antenna (3, 10), a receiver (4), and a second array antenna (5, 10). It comprises. Here, the transmitter (2) transmits a radio signal. The first array antenna (3, 10) is connected to the transmitter. The receiver (4) receives a radio signal. The second array antenna (5, 10) is connected to the receiver. Each of the first array antenna (3, 10) and the second array antenna (5, 10) includes a dielectric substrate (13) and a plurality of circular loop antennas (12). Here, the dielectric substrate (13) has an upper surface that is one surface and a lower surface that is the other surface opposite to the upper surface. The plurality of circular loop antennas (12) are formed on the upper and lower surfaces of the dielectric substrate (13), and are concentrically arranged so as to share the center point (O). Each of the i-th circular loop antennas included in the plurality of circular loop antennas (12) has a different radius a _i . Here, the order of the symbol i is the same order as the magnitude relationship of the radius a _i . Perimeter 2Paiei _i, each having the i-th circular loop antenna is m _i times the wavelength λ corresponding to the communication frequency. Here m _i is a natural number, and magnitude of a natural number m _i is the same order as the sign _i. Each of the circular loop antennas (12A to 12D) includes an upper surface pattern (14A to 14D), a lower surface pattern (15A to 15D), a first power feeding unit (21), and a second power feeding unit (22). . Here, the upper surface patterns (14A to 14D) are arranged on the upper surface of the dielectric substrate (13). The lower surface patterns (15A to 15D) are arranged on the lower surface of the dielectric substrate (13). The first power feeding section (21) includes a first electrode (19) provided at one end of the upper surface pattern (14A to 14D) and a second electrode (20) provided at one end of the lower surface pattern (15A to 15D). including. The second power feeding unit (22) includes a third electrode (19) provided at the other end of the upper surface pattern (14A to 14D) and a fourth electrode (20 provided at the other end of the lower surface pattern (15A to 15D). ). n is an arbitrary integer, and in each of the i-th circular loop antennas (12A to 12D), a first radius passing through the center point (O) and the first feeding part (21), and the center point (O) and the first point the angle between the second radius passing through the second feeding part (22) is equal to (2n + 1) π / 2m i.

  According to the embodiment, it is possible to realize a wireless communication system in which a transmission rate per frequency is improved by using an array antenna having a simple structure and being inexpensive and excellent in mass productivity.

FIG. 1 is a block circuit diagram illustrating a configuration example of a wireless communication system according to an embodiment. FIG. 2 is an overhead view showing a configuration example of the array antenna according to the embodiment. FIG. 3A is a top view illustrating a configuration example of a circular loop antenna group according to an embodiment. FIG. 3B is a partial top view illustrating a configuration example of a top pattern group according to an embodiment. FIG. 3C is a partial top view showing a configuration example of a bottom surface pattern group according to one embodiment. FIG. 4 is a cross-sectional view showing a configuration example of an array antenna according to an embodiment. FIG. 5 is an overhead view showing a configuration example of the power feeding unit according to the embodiment. FIG. 6A is a graph illustrating an example of a change in reflection loss with respect to frequency of an array antenna according to an embodiment. FIG. 6B is a graph showing an example of inter-antenna passing characteristics to each feeding part of another circular loop antenna when the first feeding part of the fourth circular loop antenna is excited in the array antenna according to the embodiment. . FIG. 6C is a graph showing an example of inter-antenna passing characteristics to each feeding part of another circular loop antenna when the first feeding part of the first circular loop antenna is excited in the array antenna according to the embodiment. . FIG. 6D is a graph showing an example of inter-antenna passing characteristics to each feeding part of another circular loop antenna when the first feeding part of the second circular loop antenna is excited in the array antenna according to the embodiment. . FIG. 6E is a graph showing an example of inter-antenna passing characteristics to each feeding part of another circular loop antenna when the first feeding part of the third circular loop antenna is excited in the array antenna according to the embodiment. . FIG. 7A is a top view illustrating a configuration example of a circular loop antenna group according to an embodiment. FIG. 7B is a partial top view showing a configuration example of a top pattern group according to an embodiment. FIG. 7C is a partial top view of an object illustrating a configuration example of a lower surface pattern group according to an embodiment. FIG. 8A is a graph illustrating an example of a change in reflection loss with respect to frequency of an array antenna according to an embodiment. FIG. 8B is a graph illustrating an example of inter-antenna passing characteristics to each feeding part of another circular loop antenna when the first feeding part of the first circular loop antenna is excited in the array antenna according to the embodiment. . FIG. 8C is a graph showing an example of inter-antenna passing characteristics to each feeding part of another circular loop antenna when the first feeding part of the second circular loop antenna is excited in the array antenna according to the embodiment. . FIG. 8D is a graph showing an example of inter-antenna passing characteristics to each feeding part of another circular loop antenna when the first feeding part of the third circular loop antenna is excited in the array antenna according to the embodiment. . FIG. 8E is a graph showing an example of inter-antenna passing characteristics to each feeding part of another circular loop antenna when the first feeding part of the fourth circular loop antenna is excited in the array antenna according to the embodiment. . FIG. 9A is a graph showing an example of a change in reflection characteristics with respect to frequency of a transmission array antenna when the array antenna including the circular loop antenna group shown in FIGS. 3A to 3C is used as a transmission array antenna and a reception array antenna. It is. FIG. 9B shows a case where the array antenna including the circular loop antenna group shown in FIGS. 3A to 3C is used as a transmission array antenna and a reception array antenna, and the first feeding unit of the first circular loop antenna is excited. It is a graph which shows an example of the passing characteristic between antennas to each electric power feeding part in a receiving antenna. FIG. 9C illustrates a case where the array antenna including the circular loop antenna group illustrated in FIGS. 3A to 3C is used as a transmission array antenna and a reception array antenna, and the first feeding unit of the second circular loop antenna is excited. It is a graph which shows an example of the passing characteristic between antennas to each electric power feeding part in a receiving antenna. FIG. 9D illustrates a case where the array antenna including the circular loop antenna group illustrated in FIGS. 3A to 3C is used as a transmission array antenna and a reception array antenna, and the first feeding unit of the third circular loop antenna is excited. It is a graph which shows an example of the passing characteristic between antennas to each electric power feeding part in a receiving antenna. FIG. 9E illustrates a case where the array antenna including the circular loop antenna group illustrated in FIGS. 3A to 3C is used as a transmission array antenna and a reception array antenna and the first feeding unit of the fourth circular loop antenna is excited. It is a graph which shows an example of the passing characteristic between antennas to each electric power feeding part in a receiving antenna. FIG. 9F illustrates a case where the array antenna including the circular loop antenna group illustrated in FIGS. 3A to 3C is used as a transmission array antenna and a reception array antenna, and the second feeding unit of the first circular loop antenna is excited. It is a graph which shows an example of the passing characteristic between antennas to each electric power feeding part in a receiving antenna. FIG. 9G illustrates a case where the array antenna including the circular loop antenna group illustrated in FIGS. 3A to 3C is used as a transmission array antenna and a reception array antenna, and the second feeding unit of the second circular loop antenna is excited. It is a graph which shows an example of the passing characteristic between antennas to each electric power feeding part in a receiving antenna. FIG. 9H illustrates a case where the array antenna including the circular loop antenna group illustrated in FIGS. 3A to 3C is used as a transmission array antenna and a reception array antenna and the second feeding unit of the third circular loop antenna is excited. It is a graph which shows an example of the passing characteristic between antennas to each electric power feeding part in a receiving antenna. FIG. 9I illustrates a case where the array antenna including the circular loop antenna group illustrated in FIGS. 3A to 3C is used as a transmission array antenna and a reception array antenna, and the second feeding unit of the fourth circular loop antenna is excited. It is a graph which shows an example of the passing characteristic between antennas to each electric power feeding part in a receiving antenna. FIG. 10A is a graph illustrating an example of a change in reflection characteristics with respect to frequency of a transmission array antenna when the array antenna including the circular loop antenna group illustrated in FIGS. 7A to 7C is used as a transmission array antenna and a reception array antenna. It is. FIG. 10B illustrates a case where the array antenna including the circular loop antenna group illustrated in FIGS. 7A to 7C is used as a transmission array antenna and a reception array antenna, and the first feeding unit of the first circular loop antenna is excited. It is a graph which shows an example of the passing characteristic between antennas to each electric power feeding part in a receiving antenna. FIG. 10C illustrates a case where the array antenna including the circular loop antenna group illustrated in FIGS. 7A to 7C is used as a transmission array antenna and a reception array antenna, and the first feeding unit of the second circular loop antenna is excited. It is a graph which shows an example of the passing characteristic between antennas to each electric power feeding part in a receiving antenna. FIG. 10D illustrates a case where the array antenna including the circular loop antenna group illustrated in FIGS. 7A to 7C is used as a transmission array antenna and a reception array antenna and the first feeding unit of the third circular loop antenna is excited. It is a graph which shows an example of the passing characteristic between antennas to each electric power feeding part in a receiving antenna. FIG. 10E illustrates a case where the array antenna including the circular loop antenna group illustrated in FIGS. 7A to 7C is used as a transmission array antenna and a reception array antenna and the first feeding unit of the fourth circular loop antenna is excited. It is a graph which shows an example of the passing characteristic between antennas to each electric power feeding part in a receiving antenna. FIG. 10F illustrates a case where the array antenna including the circular loop antenna group illustrated in FIGS. 7A to 7C is used as a transmission array antenna and a reception array antenna, and the second feeding unit of the first circular loop antenna is excited. It is a graph which shows an example of the passing characteristic between antennas to each electric power feeding part in a receiving antenna. FIG. 10G illustrates a case where the array antenna including the circular loop antenna group illustrated in FIGS. 7A to 7C is used as a transmission array antenna and a reception array antenna, and the second feeding unit of the second circular loop antenna is excited. It is a graph which shows an example of the passing characteristic between antennas to each electric power feeding part in a receiving antenna. FIG. 10H shows a case where an array antenna including the circular loop antenna group shown in FIGS. 7A to 7C is used as a transmission array antenna and a reception array antenna, and the second feeding portion of the third circular loop antenna is excited. It is a graph which shows an example of the passing characteristic between antennas to each electric power feeding part in a receiving antenna. FIG. 10I illustrates a case where the array antenna including the circular loop antenna group illustrated in FIGS. 7A to 7C is used as a transmission array antenna and a reception array antenna and the second feeding unit of the fourth circular loop antenna is excited. It is a graph which shows an example of the passing characteristic between antennas to each electric power feeding part in a receiving antenna.

  With reference to the accompanying drawings, embodiments for implementing an array antenna and a wireless communication system according to the present invention will be described below.

(First embodiment)
With reference to FIG. 1, the radio | wireless communications system 1 by this embodiment is demonstrated. FIG. 1 is a block circuit diagram illustrating a configuration example of a wireless communication system 1 according to an embodiment.

  Components of the wireless communication system 1 in FIG. 1 will be described. The wireless communication system 1 in FIG. 1 includes a transmitter 2, a transmission array antenna 3, a receiver 4, and a reception array antenna 5.

  The connection relationship of the components of the wireless communication system 1 in FIG. 1 will be described. The transmitter 2 and the transmission array antenna 3 are electrically connected, preferably via a plurality of wires. Similarly, the receiver 4 and the receiving array antenna 5 are electrically connected, preferably via a plurality of wires. The transmission array antenna 3 and the reception array antenna 5 are connected by a wireless transmission 6.

  The operation of the components of the wireless communication system 1 in FIG. 1 will be described. The transmitter 2 generates a transmission signal and transmits it to the transmission array antenna 3. The transmission array antenna 3 converts the received transmission signal into a radio signal having a predetermined communication frequency and transmits it to the reception array antenna 5. The reception array antenna 5 converts the received radio signal into a reception signal and transmits it to the receiver 4. The receiver 4 receives a reception signal.

  Since the configurations and operations of the transmitter 2 and the receiver 4 are known techniques, further detailed description is omitted. Hereinafter, the transmission array antenna 3 and the reception array antenna 5 will be described.

  In the present embodiment, the configurations of the transmission array antenna 3 and the reception array antenna 5 in FIG. 1 are basically the same. Hereinafter, when the transmitting array antenna 3 and the receiving array antenna 5 are not distinguished, they are simply referred to as “array antennas”.

  The array antenna 10 according to the present embodiment will be described with reference to FIG. FIG. 2 is an overhead view showing a configuration example of the array antenna 10 according to the embodiment.

  The components of the array antenna 10 of FIG. 2 will be described. The array antenna 10 includes a reflecting plate 11 and a circular loop antenna group 12. The reflector 11 is preferably a good conductor metal reflector.

  The positional relationship of the components of the array antenna 10 in FIG. 2 will be described. The reflector 11 and the circular loop antenna group 12 have a planar shape and are arranged in parallel to each other. The distance between the reflector 11 and the circular loop antenna group 12 is referred to as d. An air layer may be disposed between the reflector 11 and the circular loop antenna group 12. When the layer disposed between the reflector 11 and the circular loop antenna group 12 is air, the distance d is shorter than one fifth of the wavelength corresponding to the communication frequency used in the array antenna 10. It is preferable.

  Since the configuration and operation of the reflecting plate 11 are known techniques, further detailed description is omitted. Hereinafter, the circular loop antenna group 12 will be described.

  The circular loop antenna group 12 according to the present embodiment will be described with reference to FIGS. 3A to 3C, 4, and 5. FIG. 3A is a top view illustrating a configuration example of the circular loop antenna group 12 according to the embodiment. FIG. 3B is a partial top view showing a configuration example of the top pattern group 14 according to the embodiment. FIG. 3C is a partial top view showing a configuration example of the bottom pattern group 15 according to the embodiment. FIG. 4 is a cross-sectional view illustrating a configuration example of the array antenna 10 according to the embodiment. FIG. 5 is an overhead view showing a configuration example of the power feeding unit 21 according to the embodiment.

  The components of the circular loop antenna group 12 according to the present embodiment will be described. The circular loop antenna group 12 includes a first circular loop antenna 12A, a second circular loop antenna 12B, a third circular loop antenna 12C, a fourth circular loop antenna 12D, and a dielectric substrate 13.

  In the present embodiment, the array antenna 10 includes four antenna elements, that is, four circular loop antennas 12A to 12D. However, this is merely an example, and the antenna elements of the array antenna 10 according to the present embodiment. The number is not limited to four.

  The first circular loop antenna 12A includes two power feeding portions 21A and 22A. Similarly, the second circular loop antenna 12B includes two power feeding units 21B and 22B. The third circular loop antenna 12C includes two power feeding units 21C and 22C. The fourth circular loop antenna 12D includes two power feeding units 21D and 22D. In the case where the power feeding units 21A to 21D and the power feeding units 22A to 22D are not distinguished, they are simply referred to as “power feeding unit 21” and “power feeding unit 22”, respectively.

  The dielectric substrate 13 has a first surface visible on the front side of the drawing and a second surface on the back side. For convenience, the first surface is referred to as the “upper surface”, and similarly the second surface is referred to as the “lower surface”. The four circular loop antennas 12 </ b> A to 12 </ b> D include upper surface patterns 14 </ b> A to 14 </ b> D disposed on the upper surface of the dielectric substrate 13, lower surface patterns 15 </ b> A to 15 </ b> D disposed on the lower surface of the dielectric substrate 13, and the dielectric substrate 13. And a plurality of vias 16 penetrating through. The upper surface patterns 14A to 14D are collectively referred to as an upper surface pattern group 14. Similarly, the lower surface patterns 15A to 15D are collectively referred to as a lower surface pattern group 15.

  In other words, each of the four circular loop antennas 12A to 12D can be roughly divided into upper surface patterns 14A to 14D disposed on the upper surface and lower surface patterns 15A to 15D disposed on the lower surface. I can do it. It can be said that FIG. 3B is a diagram in which only the top surface patterns 14A to 14D are extracted from the circular loop antennas 12A to 12D illustrated in FIG. 3A. Similarly, it can be said that FIG. 3C is a diagram in which only the lower surface patterns 15A to 15D are extracted from the circular loop antennas 12A to 12D illustrated in FIG. 3A. However, since the lower surface patterns 15A to 15D in FIG. 3C exist on the other side of the dielectric substrate 13, they are indicated by broken lines in the transmission diagram.

  The positional relationship and connection relationship of the components of the circular loop antenna group 12 according to the present embodiment will be described. A total of four circular loop antennas 12 </ b> A to 12 </ b> D are concentrically arranged on the surface of the dielectric substrate 13 so as to share the respective center points. Here, the center point shared by the circular loop antennas 12A to 12D is referred to as a center point O.

  A difference in the perimeter of each of the circular loop antennas 12A to 12D will be described. In this embodiment, the circumference of the first circular loop antenna 12A is equal to the wavelength λ corresponding to the communication frequency. However, in practice, it is known that this perimeter may exhibit better antenna characteristics if it includes some error with respect to this wavelength. Therefore, here, even if there is some error, the expression “equal” is used. In other words, the expression “equal” may include some error.

The peripheral length of the second circular loop antenna 12B in this embodiment is equal to twice the wavelength λ corresponding to the communication frequency. In other words, the circumference of the second circular loop antenna 12B is equal to twice the circumference of the first circular loop antenna 12A. In other words Moreover, the radius _{a 2} of the second circular loop antenna 12B is equal to twice the radius _{a 1} of the first circular loop antenna 12A.

  Similarly, the perimeters of the third circular loop antenna 12C and the fourth circular loop antenna 12D in this embodiment are equal to 3 times and 4 times the wavelength λ corresponding to the communication frequency, respectively.

In other words, generalizing the relationship between the numbers and the perimeters of the circular loop antennas 12A to 12D can be expressed by the following equation (1).
2πa _i ≈ iλ (1)
Here, the constant “π” is the pi, the number “i” is an arbitrary integer included in the range of 1 to 4, and the length “a _i ” is the radius of the i-th circular loop antennas 12A to 12D. The length “λ” is a wavelength corresponding to the communication frequency. The magnitude relationship of the radius a _i is preferably in the same order as that of the number i.

  In the present embodiment, the smallest first circular loop antenna 12A has a peripheral length equal to the wavelength, and the largest fourth circular loop antenna 12D has a peripheral length equal to four times the wavelength. These are merely examples and do not limit the configuration of the array antenna 10 according to the present embodiment. In the present embodiment, the quotient obtained by dividing the perimeter of the circular loop antennas 12A to 12D by the wavelength λ is a continuous integer 1 to 4, but this feature is also merely an example, and the array antenna according to the present embodiment The ten configurations are not limited.

In other words, when the above formula (1) is further generalized, the relationship between the numbers and the perimeters of the circular loop antennas 12A to 12D can be expressed by the following formula (2).
_{2πa i ≒ m i λ ... (} 2)
Here, the constant “π” is the pi, the number “i” is an arbitrary integer included in the range of 1 to 4, and the length “a _i ” is the radius of the i-th circular loop antennas 12A to 12D. “M _i ” is an arbitrary natural number, and length “λ” is a wavelength corresponding to the communication frequency.

  It will be described that each of the circular loop antennas 12 </ b> A to 12 </ b> D is partially arranged on the upper surface and the lower surface of the dielectric substrate 13. As described above, among the circular loop antennas 12A to 12D, the upper surface patterns 14A to 14D are disposed on the upper surface of the dielectric substrate 13, and the lower surface patterns 15A to 15D are disposed on the lower surface of the dielectric substrate 13. Has been placed. In the top view of FIG. 3A and the partial top view of FIG. 3C, the lower surface pattern group 15 arranged on the back side of the dielectric substrate 13 is indicated by a broken line. 4 shows the positional relationship in the thickness direction among the reflector 11, the dielectric substrate 13, the upper surface pattern group 14, and the lower surface pattern group 15 in the array antenna 10, and the cross sectional line AA shown in FIG. It is shown as a cross-sectional view.

  The fact that the first circular loop antenna 12A shown in FIG. 5 includes two power feeding portions 21A and 22A will be described. Note that the second circular loop antenna 12B also includes two power feeding portions 21B and 22B. The third circular loop antenna 12C also includes two power feeding units 21C and 22C. Further, the fourth circular loop antenna 12D is also provided with two feeding parts 21D and 22D. Here, the power feeding unit 21A of the first circular loop antenna 12A will be described as a representative, and detailed description of other power feeding units 22A, 21B, 22B, 21C, 22C, 21D, and 22D that are similarly configured will be omitted. .

  When attention is paid to the upper surface pattern 14A of the first circular loop antenna 12A shown in FIG. 5, an upper surface power feeding portion 17A is provided at one end thereof, and an electrode 19 is provided at an end portion of the upper surface power feeding portion 17A. Similarly, when attention is paid to the lower surface pattern 15A of the first circular loop antenna 12A, a lower surface power supply portion 18A is provided at one end thereof, and a via 16 is connected to an end portion of the lower surface power supply portion 18A. An electrode 20 is provided at the end of the electrode. The electrode 19 and the electrode 20 are collectively referred to as a first power feeding unit 21A.

  Although not shown, another upper surface power supply portion 17A and another electrode 19 are provided at the other end of the upper surface pattern 14A, and another lower surface power supply portion 18A is provided at the other end of the lower surface pattern 15A. Further, another via 16 is connected to another lower surface power feeding portion 18A, and another electrode 20 is provided at an end of the other via 16. Another electrode 19 and another electrode 20 are collectively referred to as a second feeding portion 22A of the first circular loop antenna 12A.

  As described above, the two circular feeding antennas 21A and 22A are provided in the first circular loop antenna 12A. Similarly, each of the second circular loop antenna 12B to the fourth circular loop antenna 12D is provided with two power feeding units 21 and 22. In the present embodiment, the power feeding units 21A to 21D and the center point O are arranged on a straight line.

  Note that, in each of the power feeding units 21 and 22, the upper surface power feeding unit 17 </ b> A and the lower surface power feeding unit 18 </ b> A preferably have such a shape that a set of both functions as a balun. Alternatively, an existing balun may be used. Further, even if the feeding portion that functions as a balun is omitted and the coaxial cable is directly connected to the antenna conductor side of the upper surface feeding portion 17A and the lower surface feeding portion 18A, multiplexing is possible if deterioration of reflection loss is allowed. .

In each of the circular loop antennas 12 </ b> A to 12 </ b> D, an angle between the two power feeding units 21 and 22 viewed from the center point O will be described. In the example of FIG. 3A, between the center point O and a straight line passing through the first feeding part 21A of the first circular loop antenna 12A and a straight line passing through the center point O and the second feeding part 22A of the first circular loop antenna 12A. The angle is θ ₁ . In other words, when viewed from the center point O, the angle between the feeding portion 21A and the feeding portion 22A is theta _1. Similarly, when viewed from the center point O, the angle between the feeding portion 21B and the feeding portion 22B is theta _2, the angle between the feeding portion 21C and the power supply portion 22C is theta _3, the feeding section 21D and the power supply unit the angle between the 22D is theta _4.

In other words, when the relationship between the numbers of the circular loop antennas 12A to 12D and the angle between the two power feeding portions 21 and 22 is generalized, it can be expressed by the following equation (3).
θ _i = (2n + 1) π / 2m _i (3)
Here, the angle “θ _i ” is an angle between the two power feeding units 21 and 22 in the i-th circular loop antennas 12 </ b> A to 12 </ b> D, the constant “π” is the circumference, and the constant “n” is an arbitrary value. It is an integer and the constant “m _i ” is an arbitrary natural number.

With reference to FIGS. 6A to 6E, the operation of the wireless communication system 1 according to the present embodiment will be described. Here, the communication frequency is 5.25 GHz (gigahertz). Further, the dielectric substrate 13 was made of an FR-4 (Frame Regentant Type 4) material having a thickness of 0.1 mm in accordance with this communication frequency. The conductor width of each circular loop antenna 12A-12D was uniformly 0.4 mm. The radii of the circular loop antennas 12A to 12D were a ₁ = 8.7 mm, a ₂ = 16.1 mm, a ₃ = 24.2 mm, and a ₄ = 32.4 mm, respectively. In the array antenna 10 thus created, the effective relative dielectric constant is 1.2, and the effective perimeters of the circular loop antennas 12A to 12D are 59 mm, 111 mm, 167 mm, and 223 mm, respectively, which are 5.25 GHz. It is approximately equal to 57 mm, 114 mm, 167 mm, and 223 mm, which are 1 time, 2 times, 3 times, and 4 times the wavelength 57 mm corresponding to the communication frequency.

  FIG. 6A is a graph showing an example of a change in reflection loss with respect to frequency when each antenna terminal of the array antenna 10 according to an embodiment is differentially excited. FIG. 6A includes a first graph S11, a second graph S22, a third graph S33, and a fourth graph S44. The first graph S11 shows a change in reflection loss with respect to frequency in the first circular loop antenna 12A. Similarly, 2nd graph S22-4th graph S44 have each shown the change of the reflective loss with respect to the frequency in 2nd circular loop antenna 12B-4th circular loop antenna 12D. At a communication frequency of 5.25 GHz, the reflection coefficient is -15 dB or less in any case. This indicates that each circular loop antenna 12A to 12D radiates the input power almost as it is.

  FIG. 6B shows inter-antenna passing to each of the feeding parts of the other circular loop antennas 12A, 12B, and 12C when the first feeding part 21D of the fourth circular loop antenna 12D is excited in the array antenna 10 according to the embodiment. It is a graph which shows an example of a characteristic. FIG. 6B includes a first graph S14, a second graph S24, a third graph S34, a fourth graph S54 (out of frame), a fifth graph S64, a sixth graph S74, and a seventh graph S84. It is out.

  FIG. 6C shows an inter-antenna pass to each of the feeding parts of the other circular loop antennas 12B, 12C, and 12D when the first feeding part 21A of the first circular loop antenna 12A is excited in the array antenna 10 according to the embodiment. It is a graph which shows an example of a characteristic. FIG. 6C includes a first graph S21, a second graph S31, a third graph S41, a fourth graph S51, a fifth graph S61, a sixth graph S71, and a seventh graph S81.

  FIG. 6D shows an inter-antenna passage to each of the feeding portions of the other circular loop antennas 12A, 12C, and 12D when the first feeding portion 21B of the second circular loop antenna 12B is excited in the array antenna 10 according to the embodiment. It is a graph which shows an example of a characteristic. FIG. 6D includes a first graph S12, a second graph S32, a third graph S42, a fourth graph S52, a fifth graph S62, a sixth graph S72, and a seventh graph S82.

  FIG. 6E shows inter-antenna passing to each feeding part of other circular loop antennas 12A, 12B, and 12D when the first feeding part 21C of the third circular loop antenna 12C is excited in the array antenna 10 according to the embodiment. It is a graph which shows an example of a characteristic. FIG. 6E includes a first graph S13, a second graph S23, a third graph S43, a fourth graph S53 (out of frame), a fifth graph S63, a sixth graph S73, and a seventh graph S83. It is out.

  6B to 6E, when the two numbers i and j are integers in the range of 1 to 8, respectively, the graph Sij is the power received by the i-th feeding unit when the j-th feeding unit is excited. Is shown. Here, when i = 1, the i-th power feeding unit is the first power feeding unit 21A of the first circular loop antenna 12A. When i = 2, the i-th feeding unit is the first feeding unit 21B of the second circular loop antenna 12B. When i = 3, the i-th feeding unit is the first feeding unit 21C of the third circular loop antenna 12C. When i = 4, the i-th feeding unit is the first feeding unit 21D of the fourth circular loop antenna 12D. When i = 5, the i-th power feeding unit is the second power feeding unit 22A of the first circular loop antenna 12A. When i = 6, the i-th feeding unit is the second feeding unit 22B of the second circular loop antenna 12B. When i = 7, the i-th feeding unit is the second feeding unit 22C of the third circular loop antenna 12C. When i = 8, the i-th power feeding unit is the second power feeding unit 22D of the fourth circular loop antenna 12D. Similarly, when j = 1, the j-th feeding unit is the first feeding unit 21A of the first circular loop antenna 12A. When j = 2, the j-th feeding unit is the first feeding unit 21B of the second circular loop antenna 12B. When j = 3, the j-th power feeding unit is the first power feeding unit 21C of the third circular loop antenna 12C. When j = 4, the j-th feeding unit is the first feeding unit 21D of the fourth circular loop antenna 12D. When j = 5, the j-th feeding unit is the second feeding unit 22A of the first circular loop antenna 12A. When j = 6, the j-th feeding unit is the second feeding unit 22B of the second circular loop antenna 12B. When j = 7, the j-th feeding unit is the second feeding unit 22C of the third circular loop antenna 12C. When j = 8, the j-th feeding unit is the second feeding unit 22D of the fourth circular loop antenna 12D.

  In any of the graphs of FIGS. 6B to 6E, the inter-antenna passing characteristics at a communication frequency of 5.25 GHz are −24 dB or less. These values are very low as the inter-antenna passing characteristics, and indicate that the radiated power is not substantially received by the other antennas constituting the array.

  In other words, when all the circular loop antennas 12A to 12D included in the array antenna 10 according to the present embodiment are used for transmission, power radiated from each antenna is received by other antennas included in the same array antenna 10. Not. That is, the radiated power is not lost in the transmitting array antenna 10, and the characteristics of the array antenna 10 are very good.

  Further, unlike the general characteristics, the passage between the two feeding parts 21 and 22 of the same circular loop antenna 12A to 12D is suppressed when one is excited. This is a result of the control of the terminal orientation shown in the above formula (3), and shows the usefulness of the array antenna 10 according to the present embodiment. In other words, the two power feeding units 21 and 22 are arranged so that the two signals applied to the two power feeding units 21 and 22 included in the same circular loop antenna 12A to 12D have a phase orthogonal relationship. Yes.

(Second Embodiment)
The circular loop antenna group 12 according to the present embodiment will be described with reference to FIGS. 7A to 7C. FIG. 7A is a top view illustrating a configuration example of the circular loop antenna group 12 according to the embodiment. FIG. 7B is a partial top view showing a configuration example of the top pattern group 14 according to the embodiment. FIG. 7C is a partial top view of an object illustrating a configuration example of the lower surface pattern group 15 according to an embodiment.

The circular loop antenna group 12 according to the present embodiment is equivalent to the circular loop antenna group 12 according to the first embodiment shown in FIGS. 3A to 3C with the following modifications. That is, the second circular loop antenna 12 </ b> B to the fourth circular loop antenna 12 </ b> D are arranged by the first angle φ ₁ to the third angle φ ₃ around the center point O and parallel to the surface of the dielectric substrate 13. , Rotate clockwise. That is, when viewed from the center point O, the angle between the first feeding part 21A of the first circular loop antenna 12A and the first feeding part 21B of the second circular loop antenna 12B is zero in the first embodiment. and although, in this embodiment, a phi _1. Similarly, when viewed from the center point O, the angle between the first feeding part 21A of the first circular loop antenna 12A and the first feeding part 21C of the third circular loop antenna 12C is zero in the first embodiment. there was, but in this embodiment is phi _2. Further, when viewed from the center point O, the angle between the first feeding part 21A of the first circular loop antenna 12A and the first feeding part 21D of the fourth circular loop antenna 12D is zero in the first embodiment. and although, in this embodiment, a phi _3.

In the example shown in FIGS. 7A to 7C, φ ₁ = 90 degrees, φ ₂ = 45 degrees, and φ ₃ = 30 degrees. However, these angles are merely examples of the configuration, and the circular loop according to the present embodiment. The configuration of the antenna group 12 is not limited.

In each circular loop antenna 12A-12D, as viewed from the center point O, the first feeding section 21, the angle between the second feeding unit 22, as in the first embodiment, theta ₁ ~ it remains of θ _4. Strictly speaking, the angle between the first power feeding unit 21 and the second power feeding unit 22 as viewed from the center point O satisfies the above-described formula (3).

With reference to FIGS. 8A to 8E, it will be described that the characteristics of the array antenna 10 according to the present embodiment change by changing the angles φ _{1 to} φ ₃ .

  FIG. 8A is a graph showing an example of a change in reflection loss with respect to frequency when each antenna terminal of the array antenna 10 according to an embodiment is differentially excited. FIG. 8A includes a first graph S11, a second graph S22, a third graph S33, and a fourth graph S44. The first graph S11 shows a change in reflection loss with respect to frequency in the first circular loop antenna 12A. Similarly, 2nd graph S22-4th graph S44 have each shown the change of the reflective loss with respect to the frequency in 2nd circular loop antenna 12B-4th circular loop antenna 12D. At a communication frequency of 5.25 GHz, the reflection coefficient is -14 dB or less in any case. This indicates that each circular loop antenna 12A to 12D radiates the input power almost as it is. However, the characteristics of the array antenna 10 of this embodiment are different from those of the first embodiment shown in FIG. 6A.

  FIG. 8B shows an inter-antenna passage to each of the feeding parts of the other circular loop antennas 12B, 12C, and 12D when the first feeding part 21A of the first circular loop antenna 12A is excited in the array antenna 10 according to the embodiment. It is a graph which shows an example of a characteristic. FIG. 8B includes a first graph S21, a second graph S31, a third graph S41, a fourth graph S51, a fifth graph S61, a sixth graph S71, and a seventh graph S81.

  FIG. 8C shows the antenna antenna passing through the other circular loop antennas 12A, 12C, and 12D when the first feeding unit 21B of the second circular loop antenna 12B is excited in the array antenna 10 according to the embodiment. It is a graph which shows an example of a characteristic. FIG. 8C includes a first graph S12, a second graph S32, a third graph S42, a fourth graph S52, a fifth graph S62, a sixth graph S72, and a seventh graph S82.

  FIG. 8D shows inter-antenna passing to each feeding part of the other circular loop antennas 12A, 12B, and 12D when the first feeding part 21C of the third circular loop antenna 12C is excited in the array antenna 10 according to the embodiment. It is a graph which shows an example of a characteristic. FIG. 8D includes a first graph S13, a second graph S23, a third graph S43, a fourth graph S53, a fifth graph S63, a sixth graph S73, and a seventh graph S83.

  FIG. 8E shows inter-antenna passing to each feeding part of the other circular loop antennas 12A, 12B, and 12C when the first feeding part 21D of the fourth circular loop antenna 12D is excited in the array antenna 10 according to the embodiment. It is a graph which shows an example of a characteristic. FIG. 8E includes a first graph S14, a second graph S24, a third graph S34, a fourth graph S54, a fifth graph S64, a sixth graph S74, and a seventh graph S84.

  The meanings of the graphs Sij illustrated in FIGS. 8B to 8E are the same as those in the cases of FIGS. 6B to 6E, respectively, and thus further detailed description thereof is omitted.

  8B to 8E, the inter-antenna passing characteristic at the communication frequency of 5.25 GHz is −26 dB or less.

As described above, in the present embodiment, as a result of changing the arrangement of the circular loop antennas 12A to 12D with respect to the center point O of the first feeding unit 21, the reflection coefficient increases by 1 dB, while the inter-antenna passing characteristic decreases by 2 dB. Yes. In other words, according to the present embodiment, the reflection coefficient and the inter-antenna passing characteristics can be changed by appropriately changing the angles φ ₁ to φ ₃ .

(Third embodiment)
In the first embodiment and the second embodiment, the characteristics of the array antenna 10 itself when one array antenna 10 is used as the transmission array antenna 3 or the reception array antenna 5 of the wireless communication system 1 have been described. In the present embodiment, characteristics of the entire radio communication system 1 when two array antennas 10 are used as the transmission array antenna 3 and the reception array antenna 5 of the radio communication system 1 will be described.

  9A to 9I, characteristics of wireless communication system 1 when array antenna 10 including circular loop antenna group 12 shown in FIGS. 3A to 3C is used as transmitting array antenna 3 and receiving array antenna 5 are used. Will be described.

  The positional relationship between the transmission array antenna 3 and the reception array antenna 5 will be described. Consider a virtual first central axis that passes through the center point O of each of the circular loop antennas 12 </ b> A to 12 </ b> D included in the transmission array antenna 3 and is orthogonal to the surface of the dielectric substrate 13 included in the transmission array antenna 3. Similarly, a virtual second central axis that passes through the center point O of each of the circular loop antennas 12 </ b> A to 12 </ b> D included in the reception array antenna 5 and is orthogonal to the surface of the dielectric substrate 13 included in the reception array antenna 5. Think. The transmitting array antenna 3 and the receiving array antenna 5 are preferably arranged so as to face each other and the two central axes coincide. At this time, it is preferable that the reflector 11 included in the transmission array antenna 3 is disposed on the side opposite to the reception array antenna 5. Similarly, the reflection plate 11 included in the reception array antenna 5 is preferably disposed on the side opposite to the transmission array antenna 3.

  FIG. 9A shows a change in reflection characteristics with respect to frequency of the transmission array antenna 3 when the array antenna 10 including the circular loop antenna group 12 shown in FIGS. 3A to 3C is used as the transmission array antenna 3 and the reception array antenna 5. It is a graph which shows an example. 9A shows the first graph S11, the second graph S22, the third graph S33, the fourth graph S44, the fifth graph S55, the sixth graph S66, the seventh graph S77, and the eighth graph S88. Including. Here, when the number i is an integer included in the range of 1 to 4, the i-th graph Sii shows the reflection characteristics when the first feeding unit 21 of the i-th circular loop antennas 12A to 12D is excited. . Further, when the number i is an integer included in the range of 5 to 8, the i-th graph Sii shows the reflection characteristics when the second feeding unit 22 of the (4 + i) circular loop antennas 12A to 12D is excited. Yes. At a communication frequency of 5.25 GHz, the reflection coefficient is -8 dB or less in any case. This indicates that each of the circular loop antennas 12 </ b> A to 12 </ b> D has characteristics that can be used as the transmission array antenna 3.

  9B uses the array antenna 10 including the circular loop antenna group 12 shown in FIGS. 3A to 3C as the transmission array antenna 3 and the reception array antenna 5, and the first feeding unit 21A of the first circular loop antenna 12A. 6 is a graph showing an example of inter-antenna passing characteristics to each of the power feeding units 21 and 22 in the receiving antenna when the signal is excited. FIG. 9B shows the first graph S9_1, the second graph S10_1, the third graph S11_1, the fourth graph S12_1, the fifth graph S13_1, the sixth graph S14_1, the seventh graph S15_1, and the eighth graph S16_1. Including.

  9C uses the array antenna 10 including the circular loop antenna group 12 shown in FIGS. 3A to 3C as the transmission array antenna 3 and the reception array antenna 5, and the first feeding portion 21B of the second circular loop antenna 12B. 6 is a graph showing an example of inter-antenna passing characteristics to each of the power feeding units 21 and 22 in the receiving antenna when the signal is excited. FIG. 9C shows the first graph S9_2, the second graph S10_2, the third graph S11_2, the fourth graph S12_2, the fifth graph S13_2, the sixth graph S14_2, the seventh graph S15_2, and the eighth graph S16_2. Including.

  9D uses the array antenna 10 including the circular loop antenna group 12 illustrated in FIGS. 3A to 3C as the transmission array antenna 3 and the reception array antenna 5, and the first feeding unit 21C of the third circular loop antenna 12C. 6 is a graph showing an example of inter-antenna passing characteristics to each of the power feeding units 21 and 22 in the receiving antenna when the signal is excited. FIG. 9D shows the first graph S9_3, the second graph S10_3, the third graph S11_3, the fourth graph S12_3, the fifth graph S13_3, the sixth graph S14_3, the seventh graph S15_3, and the eighth graph S16_3. Including.

  9E uses the array antenna 10 including the circular loop antenna group 12 shown in FIGS. 3A to 3C as the transmission array antenna 3 and the reception array antenna 5, and the first feeding unit 21D of the fourth circular loop antenna 12D. 6 is a graph showing an example of inter-antenna passing characteristics to each of the power feeding units 21 and 22 in the receiving antenna when the signal is excited. FIG. 9E shows the first graph S9_4, the second graph S10_4, the third graph S11_4, the fourth graph S12_4, the fifth graph S13_4, the sixth graph S14_4, the seventh graph S15_4, and the eighth graph S16_4. Including.

  9F uses the array antenna 10 including the circular loop antenna group 12 shown in FIGS. 3A to 3C as the transmission array antenna 3 and the reception array antenna 5, and the second feeding portion 22A of the first circular loop antenna 12A. 6 is a graph showing an example of inter-antenna passing characteristics to each of the power feeding units 21 and 22 in the receiving antenna when the signal is excited. FIG. 9F shows the first graph S9_5, the second graph S10_5, the third graph S11_5, the fourth graph S12_5, the fifth graph S13_5, the sixth graph S14_5, the seventh graph S15_5, and the eighth graph S16_5. Including.

  9G uses the array antenna 10 including the circular loop antenna group 12 illustrated in FIGS. 3A to 3C as the transmission array antenna 3 and the reception array antenna 5, and the second feeding unit 22B of the second circular loop antenna 12B. 6 is a graph showing an example of inter-antenna passing characteristics to each of the power feeding units 21 and 22 in the receiving antenna when the signal is excited. FIG. 9G shows the first graph S9_6, the second graph S10_6, the third graph S11_6, the fourth graph S12_6, the fifth graph S13_6, the sixth graph S14_6, the seventh graph S15_6, and the eighth graph S16_6. Including.

  9H uses the array antenna 10 including the circular loop antenna group 12 illustrated in FIGS. 3A to 3C as the transmission array antenna 3 and the reception array antenna 5, and the second feeding unit 22C of the third circular loop antenna 12C. 6 is a graph showing an example of inter-antenna passing characteristics to each of the power feeding units 21 and 22 in the receiving antenna when the signal is excited. FIG. 9H shows the first graph S9_7, the second graph S10_7, the third graph S11_7, the fourth graph S12_7, the fifth graph S13_7, the sixth graph S14_7, the seventh graph S15_7, and the eighth graph S16_7. Including.

  9I uses the array antenna 10 including the circular loop antenna group 12 shown in FIGS. 3A to 3C as the transmission array antenna 3 and the reception array antenna 5, and the second feeding part 22D of the fourth circular loop antenna 12D. 6 is a graph showing an example of inter-antenna passing characteristics to each of the power feeding units 21 and 22 in the receiving antenna when the signal is excited. FIG. 9I shows the first graph S9_8, the second graph S10_8, the third graph S11_8, the fourth graph S12_8, the fifth graph S13_8, the sixth graph S14_8, the seventh graph S15_8, and the eighth graph S16_8. Including.

  9B to 9I, when the number i is an integer in the range of 9 to 12 and the number j is an integer in the range of 1 to 4, the graph Si_j is the j-th circle of the transmission array antenna 3. The inter-antenna passing characteristic to the 1st electric power feeding part 21 of the (i-8) circular loop antenna 12A-12D of the receiving array antenna 5 at the time of exciting the 1st electric power feeding part 21 of the loop antennas 12A-12D is shown. When the number i is an integer in the range of 9 to 12 and the number j is an integer in the range of 5 to 8, the graph Si_j is the (j-4) th circular loop antenna 12A of the transmission array antenna 3. The inter-antenna passing characteristic to the 1st electric power feeding part 21 of the (i-8) circular loop antenna 12A-12D of the receiving array antenna 5 at the time of exciting the 12th 2nd electric power feeding part 22 is shown. When the number i is an integer in the range of 13 to 16 and the number j is an integer in the range of 1 to 4, the graph Si_j is the number of the j-th circular loop antennas 12A to 12D of the transmission array antenna 3. The inter-antenna passing characteristics to the first feeding unit 21 of the (i-12) -th circular loop antennas 12A to 12D of the receiving array antenna 5 when the one feeding unit 21 is excited are shown. When the number i is an integer in the range of 13 to 16 and the number j is an integer in the range of 5 to 8, the graph Si_j is the (j-4) th circular loop antenna 12A of the transmission array antenna 3. The inter-antenna passing characteristic to the 1st electric power feeding part 21 of the (i-12) circular loop antenna 12A-12D of the receiving array antenna 5 at the time of exciting the 12th 2nd electric power feeding part 22 is shown.

In any case of FIGS. 9B to 9I, in the combination of the feeding units 21 and 22 facing the same direction of the circular loop antenna having the same radius between the transmission array antenna 3 and the reception array antenna 5, the inter-antenna passing characteristic is obtained. Is the largest. In other words, the inter-antenna passing characteristic of the graph represented by the following formula (4) is maximum as compared with other graphs.
S (i + 8) _i (4)
Here, the number “i” is an integer in the range of 1-8.

On the other hand, between the transmission array antenna 3 and the reception array antenna 5, in the combination of the feeding units 21 and 22 facing the directions different from each other by the angle determined by the above equation (3) of the circular loop antenna having the same radius, Inter-antenna passing characteristics are lower. In other words, the inter-antenna pass characteristic of the graph satisfying the following formula (5) or (6) is lower than the inter-antenna pass characteristic of the graph satisfying the above formula (4).
S (i + 12) _i (5)
S (i + 4) _i (6)
Here, the number “i” is an integer in the range of 1-8.

  For example, in any one of FIGS. 9B to 9I, the inter-antenna pass characteristic of the graph represented by the above formula (4) and the graph represented by the above formula (5) or (6) The combination with the smallest difference from the inter-antenna pass characteristic is the graph S16_8 and the graph S12_8 in FIG. 9I, and the difference is larger than 13 dB. In this combination, the graph S16_8 shows the carrier wave on which the desired signal is carried, that is, the intensity of the signal wave, and the graph S12_8 shows the carrier wave on which the unwanted signal is carried, that is, the intensity of the interference wave. In other words, if the intensity difference between the new wave and the interference wave is at least 13 dB or more, multiplex communication is possible. Further, in the examples of FIGS. 9B to 9I, the intensity difference in the other combinations is larger than 13 dB, so that a maximum of 8 multiplex communications is possible. In addition, if these intensity differences are larger, the performance of multiplex communication is further improved.

  Referring to FIGS. 10A to 10I, characteristics of wireless communication system 1 when array antenna 10 including circular loop antenna group 12 shown in FIGS. 7A to 7C is used as transmitting array antenna 3 and receiving array antenna 5. Will be described.

  FIG. 10A shows a change in reflection characteristics with respect to frequency of the transmission array antenna 3 when the array antenna 10 including the circular loop antenna group 12 shown in FIGS. 7A to 7C is used as the transmission array antenna 3 and the reception array antenna 5. It is a graph which shows an example. FIG. 10A shows the first graph S11, the second graph S22, the third graph S33, the fourth graph S44, the fifth graph S55, the sixth graph S66, the seventh graph S77, and the eighth graph S88. Including. Here, when the number i is an integer included in the range of 1 to 4, the i-th graph Sii shows the reflection characteristics when the first feeding unit 21 of the i-th circular loop antennas 12A to 12D is excited. . Further, when the number i is an integer included in the range of 5 to 8, the i-th graph Sii shows the reflection characteristics when the second feeding unit 22 of the (4 + i) circular loop antennas 12A to 12D is excited. Yes. At a communication frequency of 5.25 GHz, the reflection coefficient is -8 dB or less in any case. This indicates that each of the circular loop antennas 12 </ b> A to 12 </ b> D has characteristics that can be used as the transmission array antenna 3.

  FIG. 10B uses the array antenna 10 including the circular loop antenna group 12 shown in FIGS. 7A to 7C as the transmission array antenna 3 and the reception array antenna 5, and the first feeding unit 21A of the first circular loop antenna 12A. 6 is a graph showing an example of inter-antenna passing characteristics to each of the power feeding units 21 and 22 in the receiving antenna when the signal is excited. FIG. 10B shows the first graph S1_9, the second graph S1_10, the third graph S1_11, the fourth graph S1_12, the fifth graph S1_13, the sixth graph S1_14, the seventh graph S1_15, and the eighth graph S1_16. Including.

  10C uses the array antenna 10 including the circular loop antenna group 12 shown in FIGS. 7A to 7C as the transmission array antenna 3 and the reception array antenna 5, and the first feeding unit 21B of the second circular loop antenna 12B. 6 is a graph showing an example of inter-antenna passing characteristics to each of the power feeding units 21 and 22 in the receiving antenna when the signal is excited. FIG. 10C shows the first graph S2_9, the second graph S2_10, the third graph S2_11, the fourth graph S2_12, the fifth graph S2_13, the sixth graph S2_14, the seventh graph S2_15, and the eighth graph S2_16. Including.

  FIG. 10D uses the array antenna 10 including the circular loop antenna group 12 shown in FIGS. 7A to 7C as the transmission array antenna 3 and the reception array antenna 5, and the first feeding portion 21C of the third circular loop antenna 12C. 6 is a graph showing an example of inter-antenna passing characteristics to each of the power feeding units 21 and 22 in the receiving antenna when the signal is excited. FIG. 10D shows the first graph S3_9, the second graph S3_10, the third graph S3_11, the fourth graph S3_12, the fifth graph S3_13, the sixth graph S3_14, the seventh graph S3_15, and the eighth graph S3_16. Including.

  FIG. 10E uses the array antenna 10 including the circular loop antenna group 12 shown in FIGS. 7A to 7C as the transmission array antenna 3 and the reception array antenna 5, and the first feeding unit 21D of the fourth circular loop antenna 12D. 6 is a graph showing an example of inter-antenna passing characteristics to each of the power feeding units 21 and 22 in the receiving antenna when the signal is excited. FIG. 10E shows the first graph S4_9, the second graph S4_10, the third graph S4_11, the fourth graph S4_12, the fifth graph S4_13, the sixth graph S4_14, the seventh graph S4_15, and the eighth graph S4_16. Including.

  FIG. 10F uses the array antenna 10 including the circular loop antenna group 12 shown in FIGS. 7A to 7C as the transmission array antenna 3 and the reception array antenna 5, and the second feeding part 22A of the first circular loop antenna 12A. 6 is a graph showing an example of inter-antenna passing characteristics to each of the power feeding units 21 and 22 in the receiving antenna when the signal is excited. FIG. 10F shows the first graph S5_9, the second graph S5_10, the third graph S5_11, the fourth graph S5_12, the fifth graph S5_13, the sixth graph S5_14, the seventh graph S5_15, and the eighth graph S5_16. Including.

  FIG. 10G uses the array antenna 10 including the circular loop antenna group 12 shown in FIGS. 7A to 7C as the transmission array antenna 3 and the reception array antenna 5, and the second feeding unit 22B of the second circular loop antenna 12B. 6 is a graph showing an example of inter-antenna passing characteristics to each of the power feeding units 21 and 22 in the receiving antenna when the signal is excited. FIG. 10G shows the first graph S6_9, the second graph S6_10, the third graph S6_11, the fourth graph S6_12, the fifth graph S6_13, the sixth graph S6_14, the seventh graph S6_15, and the eighth graph S6_16. Including.

  10H uses the array antenna 10 including the circular loop antenna group 12 shown in FIGS. 7A to 7C as the transmission array antenna 3 and the reception array antenna 5, and the second feeding part 22C of the third circular loop antenna 12C. 6 is a graph showing an example of inter-antenna passing characteristics to each of the power feeding units 21 and 22 in the receiving antenna when the signal is excited. FIG. 10H shows the first graph S7_9, the second graph S7_10, the third graph S7_11, the fourth graph S7_12, the fifth graph S7_13, the sixth graph S7_14, the seventh graph S7_15, and the eighth graph S7_16. Including.

  FIG. 10I uses the array antenna 10 including the circular loop antenna group 12 shown in FIGS. 7A to 7C as the transmission array antenna 3 and the reception array antenna 5, and the second feeding unit 22D of the fourth circular loop antenna 12D. 6 is a graph showing an example of inter-antenna passing characteristics to each of the power feeding units 21 and 22 in the receiving antenna when the signal is excited. FIG. 10I shows the first graph S8_9, the second graph S8_10, the third graph S8_11, the fourth graph S8_12, the fifth graph S8_13, the sixth graph S8_14, the seventh graph S8_15, and the eighth graph S8_16. Including.

  10B to 10I, when the number i is an integer in the range of 1 to 4 and the number j is an integer in the range of 9 to 12, the graph Si_j is the i-th circle of the transmission array antenna 3. The inter-antenna passing characteristics to the 1st electric power feeding part 21 of the (j-8) circular loop antenna 12A-12D of the receiving array antenna 5 at the time of exciting the 1st electric power feeding part 21 of the loop antennas 12A-12D are shown. When the number i is an integer in the range of 5 to 8 and the number j is an integer in the range of 9 to 12, the graph Si_j is the (i-4) th circular loop antenna 12A of the transmission array antenna 3. The inter-antenna passing characteristic to the 1st electric power feeding part 21 of the (j-8) circular loop antenna 12A-12D of the receiving array antenna 5 at the time of exciting the 12th electric power feeding part 22 of 12D is shown. When the number i is an integer in the range of 1 to 4 and the number j is an integer in the range of 13 to 16, the graph Si_j is the number of the i-th circular loop antennas 12A to 12D of the transmission array antenna 3. The inter-antenna passing characteristics to the first feeding unit 21 of the (j-12) -th circular loop antennas 12A to 12D of the receiving array antenna 5 when the one feeding unit 21 is excited are shown. When the number i is an integer in the range of 5 to 8 and the number j is an integer in the range of 13 to 16, the graph Si_j represents the (i-4) th circular loop antenna 12A of the transmission array antenna 3. The inter-antenna passing characteristic to the 1st electric power feeding part 21 of the (j-12) circular loop antenna 12A-12D of the receiving array antenna 5 at the time of exciting the ~ 12D 2nd electric power feeding part 22 is shown.

10B to 10I, in the combination of the feeding units 21 and 22 of the circular loop antenna having the same radius and facing in the same direction between the transmission array antenna 3 and the reception array antenna 5, the inter-antenna passing characteristics. Is the largest. In other words, the inter-antenna passing characteristic of the graph represented by the following formula (7) is maximum as compared with other graphs.
Si_ (i + 8) (7)
Here, the number “i” is an integer in the range of 1-8.

On the other hand, between the transmission array antenna 3 and the reception array antenna 5, in the combination of the feeding units 21 and 22 facing the directions different from each other by the angle determined by the above equation (3) of the circular loop antenna having the same radius, Inter-antenna passing characteristics are lower. In other words, the inter-antenna pass characteristic of the graph satisfying the following formula (8) or (9) is lower than the inter-antenna pass characteristic of the graph represented by the above formula (7).
Si_ (i + 12) (8)
Si_ (i + 4) (9)
Here, the number “i” is an integer in the range of 1-8.

  For example, in any one of FIGS. 10B to 10I, the inter-antenna passing characteristics of the graph satisfying the above equation (7) and the antennas of the graph represented by the above equation (8) or (9) The combination having the smallest difference from the pass characteristic is the graph S3_11 and the graph S3_15 in FIG. 10D, and the difference is larger than 18 dB. That is, the intensity difference is improved by 5 dB compared to the cases of FIGS. 9B to 9I. Accordingly, in this case, a maximum of 8 multiplex communications are possible.

  As described above, in the array antenna 10 having the configuration according to the first embodiment, even if the radii of the circular loop antennas 12A to 12D are equal, if the directions with respect to the center point O of the power feeding units 21 and 22 are different, the antennas pass between the antennas. Characteristics can be suppressed. In short-range wireless communication in which a pair of such circular loop antennas 12A to 12D are arranged close to each other, as described in the third embodiment, 8-level multiplexing, which is twice the number of antenna elements of the array antenna 10, is performed. Can be realized.

  Moreover, in the array antenna 10 having the configuration according to the second embodiment, it is possible to suppress passage of the same array antenna 10 to other circular loop antennas, and as a result, further communication compared to the first embodiment. The performance can be improved.

  The above feature realizes not only the short-range wireless communication but also the increase of the multiplicity of the orbital angular momentum mode and the improvement of the orthogonality, and is also effective in the long-range OAM communication.

  Furthermore, in the wireless communication system 1 having the configuration according to the third embodiment, a carrier wave carrying a signal independent of each other can be input to each of the power feeding units 21 and 22 of the transmission array antenna 3. At this time, the presence of the signal is arbitrary. For example, when the first signal sequence and the second signal sequence are to be transmitted, the first carrier wave carrying the first signal sequence is input to one of the power supply units 21 of the same circular loop antenna 12A to 12D, and the other power supply unit 22 is input. The second carrier wave carrying the second signal sequence may be input to the.

  Also, a carrier wave on which the first signal series and the second signal series are combined is input to one power supply unit 21, and the first combined wave of the first signal series and the second signal sequence is input to the other power supply unit 22. May receive another carrier wave carrying another primary coupled wave. In this case, the transmitted signals are mixed at the time of reception, but this mixing is linear, and therefore can be separated by signal processing after reception. If this method is used, a signal transmitted by OAM communication having discretely changed phases can be processed at the time of reception.

  The invention made by the inventor has been specifically described based on the embodiment. However, the present invention is not limited to the embodiment, and various modifications can be made without departing from the scope of the invention. Needless to say. In addition, the features described in the embodiments can be freely combined within a technically consistent range.

DESCRIPTION OF SYMBOLS 1 Wireless communication system 2 Transmitter 3 Transmitting array antenna 4 Receiver 5 Receiving array antenna 6 Wireless transmission 10 Array antenna 11 Reflector 12 Circular loop antenna (group)
12A to 12D Circular loop antenna 13 Dielectric substrate 14 Upper surface pattern (group)
14A-14D Upper surface pattern 15 Lower surface pattern (group)
15A~15D lower surface pattern 16 via 17A top feeding portion 18A the underside feeding portion 19 electrode 20 electrode 21,21A~21D feeding portion 22,22A~22D feeding portion a ₁ ~a ₄ radial d distance O central point theta ₁ through? ₄ angle φ ₁ ~φ ₃ angle

Claims (10)

A dielectric substrate having an upper surface that is one surface and a lower surface that is the other surface opposite to the upper surface;
A plurality of circular loop antennas formed on the upper and lower surfaces of the dielectric substrate and arranged concentrically so as to share respective center points;
Each of the i-th circular loop antennas included in the plurality of circular loop antennas has a different radius a _i , where the order of the symbols i is the same order as the magnitude relationship of the radius a _i ,
Perimeter 2Paiei _i wherein each of the i circular loop antenna having is m _i times the wavelength λ corresponding to the communication frequency, where m _i is a natural number, and wherein the magnitude of a natural number m _i code in the same order as _i ,
Each circular loop antenna is
An upper surface pattern disposed on the upper surface of the dielectric substrate;
A lower surface pattern disposed on the lower surface of the dielectric substrate;
A first power feeding unit including a first electrode provided at one end of the upper surface pattern and a second electrode provided at one end of the lower surface pattern;
Comprising a second electrode including a third electrode provided at the other end of the upper surface pattern and a fourth electrode provided at the other end of the lower surface pattern;
n is an arbitrary integer, and in each of the i-th circular loop antennas, a first radius passing through the center point and the first feeding portion, and a second radius passing through the center point and the second feeding portion, the angle between, (2n + 1) π / 2m i equal array antenna. The array antenna according to claim 1, wherein
The center point and the first feeding part of each circular loop antenna are arranged on a straight line. The array antenna according to claim 1, wherein
In an arbitrary combination of a first circular loop antenna and a second circular loop antenna included in the plurality of circular loop antennas, the first feeder of the first circular loop antenna and the first of the second circular loop antenna. A direction different from the feeding point with respect to the center point is an array antenna. In the array antenna as described in any one of Claims 1-3,
Further comprising a reflector disposed parallel to the dielectric substrate;
A distance between the dielectric substrate and the reflecting plate is shorter than one fifth of the wavelength. A transmitter for transmitting radio signals;
A first array antenna connected to the transmitter;
A receiver for receiving the radio signal;
A second array antenna connected to the receiver;
Each of the first array antenna and the second array antenna is
A dielectric substrate having an upper surface that is one surface and a lower surface that is the other surface opposite to the upper surface;
A plurality of circular loop antennas formed on the upper and lower surfaces of the dielectric substrate and arranged concentrically so as to share respective center points;
Each of the i-th circular loop antennas included in the plurality of circular loop antennas has a different radius a _i , where the order of the symbols i is the same order as the magnitude relationship of the radius a _i ,
Perimeter 2Paiei _i wherein each of the i circular loop antenna having is m _i times the wavelength λ corresponding to the communication frequency, where m _i is a natural number, and wherein the magnitude of a natural number m _i code in the same order as _i ,
Each circular loop antenna is
An upper surface pattern disposed on the upper surface of the dielectric substrate;
A lower surface pattern disposed on the lower surface of the dielectric substrate;
A first power feeding unit including a first electrode provided at one end of the upper surface pattern and a second electrode provided at one end of the lower surface pattern;
Comprising a second electrode including a third electrode provided at the other end of the upper surface pattern and a fourth electrode provided at the other end of the lower surface pattern;
n is an arbitrary integer, and in each of the i-th circular loop antennas, a first radius passing through the center point and the first feeding portion, and a second radius passing through the center point and the second feeding portion, The angle between is equal to (2n + 1) π / 2m _i wireless communication system. The wireless communication system according to claim 5, wherein
In each of the first array antenna and the second array antenna, the center point and the first feeding unit of each circular loop antenna are arranged on a straight line. The wireless communication system according to claim 5, wherein
In each of the first array antenna and the second array antenna, in any combination of the first circular loop antenna and the second circular loop antenna included in the plurality of circular loop antennas, the first circular loop antenna includes the first circular antenna. A wireless communication system in which one feeding unit and the first feeding unit of the second circular loop antenna have different directions as viewed from the center point. In the radio communication system according to any one of claims 5 to 7,
Each of the first array antenna and the second array antenna is
A wireless communication system further comprising a reflector arranged in parallel to the dielectric substrate. In the communication system according to any one of claims 5 to 7,
Each of the first array antenna and the second array antenna is
A virtual central axis passing through the central point and orthogonal to the dielectric substrate;
The wireless communication system, wherein the first array antenna and the second array antenna are arranged such that the central axis of the first array antenna and the central axis of the second array antenna coincide with each other. The wireless communication system according to claim 9, wherein
The first array antenna is
A first reflector arranged in parallel to the dielectric substrate and opposite to the second array antenna;
The second array antenna is
A wireless communication system, further comprising: a second reflector disposed in parallel to the dielectric substrate and on the side opposite to the first array antenna.