WO2014021081A1 - Antenna apparatus - Google Patents

Description

Antenna device

The present invention relates to an antenna device including a feeding radiation electrode connected to a feeding point and a parasitic radiation electrode connected to a ground conductor, and in particular, mobile communication devices such as mobile phone terminals and GPS receivers, and wireless devices. The present invention relates to a small antenna device used in an electronic device having a wireless communication function such as a LAN.

For example, Patent Documents 1 and 2 disclose antennas provided in mobile communication devices and electronic devices having a wireless communication function.

FIG. 10 is a plan view of the antenna device disclosed in Patent Document 1. FIG. In the example of FIG. 10, the radiation electrode 3 (31, 32, 33, 34) of the antenna is formed on the substrate, a plurality of reactance elements 5 and 6 are inserted in the middle of the radiation electrode, and the feeding electrode 2 and the radiation electrode 3 is inserted in the inductor 11. With this configuration, the resonance frequencies of the fundamental mode and the higher-order mode of the radiation electrode 3 can be adjusted by determining the reactance of the reactance elements 5 and 6.

FIG. 11 is a perspective view of a chip antenna provided in the antenna device disclosed in Patent Document 2. FIG. In FIG. 11, the chip antenna 20 is formed on a base body 21, first and second radiation electrodes 22 and 23 constituting comb-shaped electrodes on the upper surface of the base body 21, and side surfaces of the base body 21, and the first radiation is formed. A feeding radiation electrode 24 connected to one end of the electrode 22, a first ground electrode 25 formed on the side surface and connected to the second radiation electrode 23, and terminal electrodes 27 to 29 formed on the bottom surface of the substrate 21. And. The first terminal electrode 27 is connected to a power supply line formed on the printed board. The second terminal electrode 28 is connected to a ground conductor on the printed board.

International Publication No. 2009/28251 JP 2011-61638 A

In the antenna device shown in FIG. 10, the resonance frequency of the fundamental mode and the higher order mode can be adjusted by changing the value of the reactance element, but the bandwidth cannot be adjusted.

In the chip antenna 20 having the radiation electrode having the shape as shown in FIG. 11, a capacitance is formed in the vicinity of the open end of the radiation electrode and the vicinity of the power feeding portion. The radiation electrode 22 and the second radiation electrode 23, which is a non-feed radiation electrode, are capacitively coupled, and a broadband characteristic is obtained by double resonance.

However, in order to achieve a wide band by obtaining double resonance characteristics by resonance by the feed radiation electrode and resonance by the feed radiation electrode, the amount of electromagnetic coupling between the feed radiation electrode and the feed radiation electrode must be optimized. For this purpose, a certain distance is required between the feeding radiation electrode and the non-feeding radiation electrode. This is one factor that prevents miniaturization.

An object of the present invention is to provide an antenna device that obtains an optimum amount of coupling between a feeding radiation electrode and a parasitic radiation electrode within a limited area, and is small in size and suitable for a plurality of frequency bands. It is in.

The antenna device of the present invention is an antenna having a base and a plurality of radiation electrodes formed on the base.
The radiation electrode includes a feed radiation electrode that resonates in a plurality of resonance modes including a higher order resonance mode, and a parasitic radiation electrode that resonates in a higher order resonance mode or a fundamental resonance mode,
Double resonance occurs between the resonance mode of the non-feed radiation electrode and the higher-order resonance mode of the feed radiation electrode at a frequency higher than the higher-order resonance mode of the feed radiation electrode,
A circuit element is connected in series to the feeding end of the feeding radiation electrode.

With this configuration, the current intensity distribution of the higher-order resonance mode of the feed radiation electrode is determined by the circuit element inserted at the feed end of the feed radiation electrode, and the resonance mode of the parasitic radiation electrode and the higher-order resonance mode of the feed radiation electrode are determined. Is determined.

The feeding radiation electrode may include a first radiation electrode and a second radiation electrode extending from the first radiation electrode.

According to the present invention, the current intensity distribution (generated magnetic field distribution) of the radiation electrode changes depending on the value of the circuit element inserted into the feeding end of the radiation electrode. Without changing the shape of the feed radiation electrode and the parasitic radiation electrode, the amount of magnetic coupling between the feed radiation electrode and the parasitic radiation electrode can be adjusted, so that a predetermined frequency characteristic can be obtained without changing the antenna electrode shape. It is done. Further, the degree of freedom in the interval between the feeding radiation electrode and the non-feeding radiation electrode is increased, and a broadband antenna device can be realized by downsizing correspondingly.

Furthermore, the frequency of the resonance mode of the non-feeding radiation electrode is higher than the frequency of the higher-order resonance mode of the feeding radiation electrode, and the two resonance modes are magnetically coupled to form a double resonance without causing an antiresonance point. Broadband by double resonance becomes possible.

FIG. 1 is a plan view of an antenna device 101 according to an embodiment of the present invention. FIG. 2 is a perspective view of the chip antenna 50. FIG. 3 is a schematic circuit diagram of the antenna device 101 shown in FIG. 4A and 4B are diagrams showing the distribution of current intensity on each electrode of the antenna device 101 in the frequency 5 GHz band. FIG. 5A is a diagram illustrating the frequency characteristics of the return loss (S11) of the antenna 101, and FIG. 5B is a diagram illustrating the frequency range of 4 GHz to 6 GHz in FIG. FIG. 6A is a diagram showing an impedance trajectory viewed from the feeding point of the antenna 101 on a Smith chart, and FIG. 6B is a diagram showing a frequency range of 4 GHz to 6 GHz in FIG. FIGS. 7A, 7B, and 7C are plan views of the antenna devices ANT3, ANT4, and ANT5. 8A is a frequency characteristic diagram of the return loss of the antenna ANT3 shown in FIG. 7A, and FIG. 8B is a frequency characteristic diagram of the return loss of the antenna ANT4 shown in FIG. 7B. FIG. 9A is a plan view of an antenna device 102 according to another embodiment, and FIG. 9B is a schematic circuit diagram thereof. FIG. 10 is a plan view of the antenna device disclosed in Patent Document 1. In FIG. FIG. 11 is a perspective view of a chip antenna provided in the antenna device disclosed in Patent Document 2. FIG.

FIG. 1 is a plan view of an antenna device 101 according to an embodiment of the present invention. The antenna device 101 includes a substrate 40, various electrodes formed on the substrate 40, a chip antenna 50 mounted on the substrate 40, and circuit elements 61 to 66.

A ground conductor 41 is formed on the front and back surfaces of the substrate 40. The ground conductors on the front and back surfaces are connected through a large number of through holes (plated through holes). A ground conductor non-formation region 42 in which no ground conductor is formed is provided on the front and back surfaces of the substrate 40, and a feeding radiation electrode and a parasitic radiation electrode are formed in the ground conductor non-formation region 42.

FIG. 2 is a perspective view of the chip antenna 50. The chip antenna 50 includes a rectangular parallelepiped dielectric base 51 and electrodes 52 and 53 formed from the lower surface to the upper surface of the dielectric base.

The first feed radiation electrode is constituted by the electrodes 45 and 46 and the electrode 53 of the chip antenna 50 shown in FIG. Further, the electrode 47 and the electrode 52 of the chip antenna 50 constitute a second feeding radiation electrode. A parasitic radiation electrode 48 is formed in the ground conductor non-forming region 42. A power supply electrode 43 and a power supply line 44 are further formed on the substrate 40.

A circuit element 63 is mounted in the middle from the first end P11 to the second end P12 of the first feed radiation electrode by the electrodes 45, 46 and the electrode 53 (position near the feed end). A circuit element 62 is mounted between the feed end (first end P11) of the first feed radiation electrode and the feed line 44. A circuit element 64 is mounted in the middle of the second feeding radiation electrode by the electrode 47 and the electrode 52 (near the branch point from the first feeding radiation electrode). Further, the first end P31 of the parasitic radiation electrode 48 is open, and the circuit element 66 is mounted between the second end P32 and the ground conductor 41. Further, a circuit element 65 is mounted between the vicinity of the second end P <b> 32 of the parasitic radiation electrode 48 and the electrode 45. A circuit element 61 is mounted between the feed line 44 and the ground conductor 41.

FIG. 3 is a schematic circuit diagram of the antenna device 101 shown in FIG. The circuit elements 62 and 63 are chip inductors, and the circuit elements 64 to 66 are chip capacitors. The circuit element 61 is a chip inductor.

Thus, the circuit element 63 is connected in series at a position near the feeding end of the first feeding radiation electrode by the electrodes 45 and 46 and the electrode 53. A circuit element 62 (inductor) is connected in series between the electrode 45 near the feeding end of the first feeding radiation electrode and the feeding line 44. In addition, a circuit element 64 (capacitor) is connected in series in the middle of the second feeding radiation electrode by the electrode 47 and the electrode 52 (near the branch point from the first feeding radiation electrode). The grounding end of the parasitic radiation electrode 48 is grounded via a circuit element 66 (capacitor). Further, a circuit element 65 (capacitor) is connected between the vicinity of the ground end of the parasitic radiation electrode 48 and the electrode 45. A circuit element 61 (inductor) is connected to the shunt between the feed line 44 and the ground conductor 41.

The circuit element 63 adjusts the frequency of the 1/4 wavelength resonance (fundamental mode) of the first feeding radiation electrode by the electrodes 45 and 46 and the electrode 53. The circuit element 64 adjusts the frequency of the quarter wavelength resonance (fundamental mode) of the second feeding radiation electrode by the electrode 47 and the electrode 52. The circuit element 66 adjusts the frequency of the 1/4 wavelength resonance (fundamental mode) of the parasitic radiation electrode 48. The circuit element 65 adjusts the frequency of the 3/4 wavelength resonance (third mode) by the first feeding radiation electrode. The circuit element 62 adjusts the current intensity distribution on the first feeding radiation electrode by the electrodes 45 and 46 and the electrode 53. As a result, as shown later, the coupling amount between the ¼ wavelength resonance of the first feeding radiation electrode and the ¼ wavelength resonance of the parasitic radiation electrode 48 is adjusted, thereby ensuring the bandwidth due to the double resonance. To do. The circuit element 61 matches the impedance of the power feeding circuit with the impedance of the antenna device.

4 (A) and 4 (B) are diagrams showing the distribution of current intensity on each electrode of the antenna device 101 in the frequency 5 GHz band (4.955 GHz). Here, the current intensity is expressed by concentration. The antenna device ANT1 shown in FIG. 4A and the antenna device ANT2 shown in FIG. The element values of each circuit element are as follows.

[Table 1]
―――――――――――――――――――――――
Circuit element ANT1 ANT2
―――――――――――――――――――――――
61 1.0nH 1.0nH
62 0.5nH 1.0nH
63 2.7nH 3.0nH
64 3.6pF 2.0pF
65 0.9pF 0.9pF
66 0.1 pF 0.1 pF
―――――――――――――――――――――――
In addition, in order to set the frequency of the 1/4 wavelength resonance of the first feeding radiation electrode and the frequency of the quarter wavelength resonance of the second feeding radiation electrode to predetermined values, the circuit element 62 is set with the inductance of the circuit element 62. The element values of 63 and 64 are also changed.

Since the circuit element 62 is inserted in series at a position near the feeding end of the first feeding radiation electrode, if the reactance of the circuit element 62 is changed, the circuit element 62 is placed on the first feeding radiation electrode by the electrodes 45 and 46 and the electrode 53. Current distribution changes, and the magnetic field strength distribution changes accordingly. The current intensity distribution on the first feeding radiation electrode, particularly the portion facing the parallel with the parasitic radiation electrode 48 (portion surrounded by an ellipse E in FIGS. 4A and 4B) is the same as that of the first feeding radiation electrode. The magnetic field coupling with the parasitic radiation electrode 48 is affected. Therefore, the amount of coupling between the first feeding radiation electrode and the non-feeding radiation electrode varies depending on the inductance of the circuit element 62. Then, the amount of coupling is optimized so as to ensure the bandwidth due to the double resonance.

FIG. 5A is a diagram showing the frequency characteristics of the return loss (S11) of the antenna 101. FIG. FIG. 6A is a diagram showing the locus of impedance viewed from the feeding point of the antenna 101 on a Smith chart. FIG. 5B is a diagram showing a frequency range of 4 GHz to 6 GHz in FIG. Similarly, FIG. 6B is a diagram illustrating a frequency range of 4 GHz to 6 GHz in FIG. In these figures, the conditions of the circuit elements that obtain the characteristics of the antenna devices ANT1 and ANT2 are as shown in Table 1.

5A and 5B, the return loss is low at the frequencies indicated by (a), (b), (c), and (d). (a) is 1.57 GHz resonance due to 1/4 wavelength resonance of the first feeding radiation electrode (45, 46, 53), and (b) に よ る is due to 1/4 wavelength resonance of the second feeding radiation electrode (47, 52). 2. 45 GHz resonance, (c) is approximately 5.0 GHz resonance due to 3/4 wavelength resonance of the first feeding radiation electrode (45, 46, 53), and (d) １ ／ is ¼ wavelength of the parasitic radiation electrode 48. The resonance is approximately 5.5 GHz due to resonance.

5 (A) and 5 (B), (c) 3/4 wavelength resonance of the first feeding radiation electrode indicated by and (d) 1/4 wavelength resonance of the parasitic radiation electrode indicated by are magnetically coupled. Thus, it is in a double resonance state. 6A and 6B, the impedance locus passes through the vicinity of the center of the Smith chart in the 5 GHz band. As apparent from FIGS. 6A and 6B, the impedance locus of ANT1 passes near the center of the Smith chart as compared with the antenna device ANT2. That is, the antenna device ANT1 is more matched. As is clear from FIG. 5B, the antenna apparatus ANT1 has a return loss of −15 dB over 5.1 to 5.6 GHz. In the antenna device ANT2, a return loss of −7 dB is obtained over 4.8 to 5.6 GHz.

The 1.5 GHz band is a GPS band, and the 2.4 GHz band and the 5 GHz band are both wireless LAN bands. In this way, it functions as a three-band antenna device.

Generally, when one end open and other end short-circuited resonators (quarter wavelength resonators, etc.) are coupled via an electric field (capacitive coupling), the resonance frequency of the resonator on the coupling side is lower. An anti-resonance point is generated. On the other hand, when coupling is performed via a magnetic field (inductive coupling), an anti-resonance point is generated on a higher frequency side than the resonance frequency of the resonator on the coupling side.

In the present embodiment, the ¼ wavelength resonance of the first feeding radiation electrode and the ¼ wavelength resonance of the parasitic radiation electrode are magnetically coupled. 5 (A) and 5 (B), the frequency of the 1/4 wavelength resonance of the parasitic radiation electrode (resonator on the coupling side) indicated by (d) is the first feeding radiation indicated by (c). Since the frequency is higher than the 3/4 wavelength resonance frequency of the electrode, an antiresonance point is generated on the side higher than the resonance frequency of (d). Therefore, double resonance occurs without affecting the passbands (c) to (d). If the frequency of the quarter-wave resonance of the parasitic radiation electrode is lower than the frequency of the quarter-wave resonance of the first feed radiation electrode, the frequency is higher than the frequency of the quarter-wave resonance of the parasitic radiation electrode. Since an anti-resonance point is generated, an anti-resonance point is generated between the two frequencies (c) and (d), and broadband characteristics cannot be obtained.

7 (A), 7 (B), and 7 (C) are plan views of the antenna devices ANT3, ANT4, and ANT5. In these examples, the range including the entire substrate is shown. The structure of the antenna device ANT3 in FIG. 7A is the same as that of the antenna device 101 shown in FIG. The extending direction of the first and second feeding radiation electrodes and the non-feeding radiation electrode is not limited to the direction along the long side of the substrate, but on the short side of the substrate 40 as shown in the antenna device ANT4 in FIG. It may be along the direction. Further, the formation positions of the first and second feed radiation electrodes and the non-feed radiation electrode are not limited to the corners of the substrate 40, but are positions along the sides as shown in the antenna device ANT5 in FIG. 7C. May be.

The element values of the circuit elements of the antenna devices ANT3, ANT4, and ANT5 shown in FIGS. 7A, 7B, and 7C are different. For example, the element values of the circuit elements of the antenna devices ANT3 and ANT4 are as follows.

[Table 2]
―――――――――――――――――――――――
Circuit element ANT3 ANT4
―――――――――――――――――――――――
61 1.0nH 1.0nH
62 1.0nH 1.0nH
63 2.7 nH 2.7 nH
64 4.0 pF 4.0 pF
65 1.3pF 1.0pF
66 0.05pF 0.05pF
―――――――――――――――――――――――
8A is a frequency characteristic diagram of the return loss of the antenna ANT3 shown in FIG. 7A, and FIG. 8B is a frequency characteristic diagram of the return loss of the antenna ANT4 shown in FIG. 7B. In FIGS. 8A and 8B, the numbers Mkr1 to Mkr7 correspond to the mark numbers represented with the triangle symbols in the characteristic diagrams. In both the antenna devices ANT3 and ANT4, low return loss characteristics are obtained in the 1.5 GHz band, the 2.4 GHz band, and the 5 GHz band.

As described above, even if the antenna device is formed at different positions on the substrate, the return loss characteristics can be obtained in a predetermined frequency band by setting the element values of the respective circuit elements.

FIG. 9A is a plan view of an antenna device 102 according to another embodiment different from the antenna device shown in FIG. The antenna device 102 includes a substrate 40, various electrodes formed on the substrate 40, and circuit elements 62 mounted on the substrate 40.

Unlike the antenna device 101 shown in FIG. 1, the antenna device 102 does not include the chip antenna 50, the electrode 47, and the circuit elements 61, 63, 64, 65, and 66. A circuit element 62 is connected in series to the feeding end of the feeding radiation electrode 46P. One end of the parasitic radiation electrode 48P is directly grounded to the ground conductor 41. Other configurations are the same as those of the antenna device 101.

FIG. 9B is a schematic circuit diagram of the antenna device 102. The circuit element 62 is a chip inductor. In this way, the circuit element 62 (inductor) is connected in series between the feeding end of the feeding radiation electrode and the feeding circuit.

The circuit element 62 adjusts the current intensity distribution of the portion surrounded by the ellipse E on the feeding radiation electrode 46P. This adjusts the amount of coupling between the ¼ wavelength resonance of the feed radiation electrode 46P and the ¼ wavelength resonance of the parasitic radiation electrode 48P, thereby ensuring a bandwidth due to double resonance.

As described above, the present invention can also be applied to an antenna device including one feeding radiation electrode and one parasitic radiation electrode.

In each of the embodiments described above, the feeding radiation electrode and the parasitic radiation electrode are configured by the electrode pattern on the substrate. However, the chip antenna is formed by forming the feeding radiation electrode and the parasitic radiation electrode on the dielectric substrate. The chip antenna may be configured and mounted on a substrate.

Further, in each of the embodiments described above, an example in which the higher-order mode of the feed radiation electrode and the fundamental mode of the feed-off radiation electrode are coupled and double-resonated has been shown. The present invention can be similarly applied to a configuration in which a higher-order mode of the radiation electrode is coupled to cause double resonance.

ANT1 to ANT5 ... antenna device P11 ... first end P12 ... second end P31 ... first end P32 ... second end 40 ... substrate 41 ... ground conductor 42 ... ground conductor non-forming region 43 ... feed electrode 44 ... feed line 45, 46, 47 ... electrode 48 ... parasitic radiation electrode 50 ... chip antenna 52, 53 ... electrodes 61-66 ... circuit elements 101, 102 ... antenna device

Claims (2)

In an antenna having a base and a plurality of radiation electrodes formed on the base,
The radiation electrode includes a feed radiation electrode that resonates in a plurality of resonance modes including a higher order resonance mode, and a parasitic radiation electrode that resonates in a higher order resonance mode or a fundamental resonance mode,
Double resonance occurs between the resonance mode of the non-feed radiation electrode and the higher-order resonance mode of the feed radiation electrode at a frequency higher than the higher-order resonance mode of the feed radiation electrode,
An antenna device, wherein a circuit element is connected in series to a feeding end of the feeding radiation electrode. The antenna device according to claim 1, wherein the feeding radiation electrode includes a first radiation electrode and a second radiation electrode extending from the first radiation electrode.

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