JP2000031721A - Built-in antenna system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small sized antenna system that is built in a portable telephone set with excellent directivity, makes reception stable through the diversity configuration and copes with two frequencies over a broad band. SOLUTION: Two helical coil elements 8, 9 made almost orthogonal to each other are built in at an upper part of a portable telephone set to attain a dipole or diversity configuration, An electromagnetic shield plate is provided in the middle or at a lower part to reduce antenna interference and to enhance the diversity effect and a feeding or a parasitic element is added to the antenna system to attain wide frequency band through electromagnetic coupling and to cope with two frequencies.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna used for a portable telephone and, more particularly, to an antenna device having a good antenna radiation characteristic incorporated in a housing.

[0002]

2. Description of the Related Art Portable telephones have been miniaturized due to innovations in communication technology, but have the following problems. A mobile phone is provided with an antenna for transmitting and receiving radio waves. FIG. 12 to ensure good antenna radiation characteristics
As shown in (a), the whip antenna 1 is pulled out at the time of communication, and only the helical antenna 2 at the top of the antenna is put out as shown in FIG. As a result, the length of the antenna protruding from the housing 3 is large, which hinders portability and design.

At the time of reception, a plurality of operations for pulling out the whip antenna 1 and pressing the reception key 4 are required, and a plurality of operations for storing the whip antenna 1 and pressing the standby key 5 are also required at the time of standby. Must be operated with both hands.

[0004] In a mobile phone of a standard that requires diversity reception, a rod antenna 6 having a whip antenna 1 and a helical antenna 2 and an inverted-F antenna 7 or a microstrip antenna built in a housing 3 are usually used. Transmit and receive with multiple antennas. As a result, portability and cost are impeded.

[0005] In addition, despite the fact that the frequency used is high, and the antenna is miniaturized and digitized, no specific countermeasure is taken in the conventional example shown in FIG. It is also difficult to take countermeasures.

Further, in order to make the whip antenna 1 of the rod antenna 6 of the conventional example broader for transmission and reception or to be able to cope with two separate frequency bands, it is necessary to ensure the reliability and workability of the material. difficult.

[0007]

In order to solve the above-mentioned problems, a built-in antenna device according to the present invention comprises two helical coil elements which are tilted substantially symmetrically with respect to a longitudinal center plane of a mobile phone, and are provided inside a housing. , Two helical coil elements are arranged in the housing so as to face upward in the vicinity of the vertical center plane of the housing.

By making the central axes of the two helical coil elements substantially orthogonal to each other, the interference of the antenna between the helical coil elements is reduced.

The two terminals of the two helical coil elements are brought to the center and connected to the positive and negative power supply parts to form a dipole configuration of two non-linear helical coil elements. Also in this case, the two helical coil elements are arranged symmetrically and inclined.

[0010] Two terminals of the two helical coil elements are connected to independent power supply sections, and a diversity configuration is formed as two independent antennas. The two helical coil elements are arranged symmetrically and inclined.

In order to reduce interference of two helical coil elements symmetrically arranged as an antenna as an antenna, an electromagnetic shielding plate for shielding electromagnetic waves is arranged in the following configuration.

An electromagnetic shielding plate is disposed near the longitudinal center plane of the housing between the two helical coil elements, almost vertically to the front surface of the housing of the portable telephone, so as to reduce the interference of the radiation of both antennas.

In the vicinity of the lower part of the two helical coil elements,
By arranging the electromagnetic shielding plate, the interference between both antenna radiations is further reduced.

A continuous electromagnetic shielding plate is arranged from the lower part of the two helical coil elements to the front side of the housing to reduce the radiation of electromagnetic waves in the front direction of the housing.

A linear or helical coil-shaped parasitic element which is symmetrically bent near the central axis of the two helical coil elements having a dipole configuration or has a common central axis is arranged to widen the target frequency band. And pluralization.

A linear passive element bent symmetrically in the vicinity of the center axis of two helical coil elements having a diversity configuration, or a feed element of two additional helical coils with a common center axis is arranged. Then, the target frequency is broadened or pluralized.

The central portion of the upper part of the housing for housing the built-in antenna is made continuously convex so as to be excellent in portability and appearance.

By winding the two helical coil elements so that the main winding surface is parallel to the longitudinal center plane of the housing, the built-in antenna can be arranged functionally with respect to restrictions in the width direction of the housing. .

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described based on examples with reference to the drawings. In FIG. 1, two helical coil elements 9 and 10 are provided at the upper part of the mobile phone so as to be symmetrically inclined with respect to the longitudinal center plane of the housing 8. The helical coil elements 9, 10 are arranged upward in the vicinity of the vertical center plane.

In the embodiments of the present invention, a helical coil element is used as the elongated antenna element of the first aspect. This is because it is the easiest to configure and the dimensionally efficient. However, as another configuration example, an antenna element in which a conductor is bent into a plurality of pieces and shortened can be used as the elongated antenna element of the first aspect.

Returning to FIG. 1, the terminals 11 and 12 of the two helical coil elements 9 and 10 are housed in the housing 8 and are connected to a transmission / reception circuit via a matching circuit (not shown). A reception speaker 14 is provided on the front surface 13 of the housing 8.

When the two helical coil elements 9 and 10 shown in FIG. 1 are installed on the upper part of the housing 8 as built-in antennas, the upper part 16 of the housing 15 is curved as shown in FIG. As shown in FIG. 2 (b), even when the upper portion 18 of the housing 17 has a linear appearance, the upper portion 16 is continuously formed such that the central portions of the upper portion 18 are convex.

Since there is no antenna protruding from the housing, it is easy to take it out when carrying it.
It is not necessary to perform a plurality of operations of pressing one or more of the standby keys 20 and 22.

As shown in FIG. 1, the center axes of the two helical coil elements 9, 10 are made substantially orthogonal to each other to reduce mutual interference between antennas. However, it can be considered as an almost independent antenna, which is necessary for a diversity configuration.

As shown in FIGS. 3, 4 and 5, the reason why an electromagnetic shielding material is used other than the orthogonal arrangement of the two helical coil elements is that the electromagnetic shielding material absorbs and attenuates electromagnetic waves from an adjacent antenna. Close or reflected
An object of the present invention is to further reduce mutual interference between antennas of the helical coil elements.

In FIG. 3, two helical coil elements 23,
An electromagnetic shielding plate 25 is disposed substantially perpendicular to the front surface 13 of the housing 8 near the vertical center plane of the housing between the housings 24 to reduce mutual interference between antennas of the adjacent helical coil elements 23 and 24. it can.

In FIG. 4, two helical coil elements 26,
By disposing the electromagnetic shielding plates 28 and 29 near the lower part of the 27, mutual interference between the antennas of the adjacent helical coil elements 26 and 27 can be reduced.

In FIG. 5, two helical coil elements 32,
33, a continuous electromagnetic shielding plate 34 is disposed on the front surface 13 side of the housing 8 so that the helical coil element
And 33, the mutual interference of the antennas can be reduced.

FIGS. 1 to 5 show the built-in antenna device of the present invention.
As shown in the embodiment, the orthogonal arrangement of two helical coil elements and mutual interference reduction by an electromagnetic shielding plate, the directivity of different antennas of the two helical coil elements by orthogonal arrangement, and the antenna of the helical coil element Can effectively detect both an electric field and a magnetic field.

Reducing the mutual interference between the antennas of the two helical coil elements is necessary for diversity reception with the two antennas. Furthermore, in a mobile phone which is miniaturized and a free arrangement of parts is restricted, there is a limit only in spatial diversity depending on a distance between antennas. Therefore, the present invention is effective for radio wave reception in which the directional diversity and the polarization diversity by two antennas having different directivities like the built-in antenna device of the present invention are stable.

The helical coil element can detect both the electric field component and the magnetic field component of the spatial electromagnetic wave from the base station, unlike a linear whip antenna or the like. Accordingly, reception can be performed on average with respect to the attitude of the mobile phone during reception or a random inclination of the polarization plane due to fading.

As shown in the embodiment of FIG. 4, power is supplied to the terminals 30 and 31 of the two helical coil elements 26 and 27 from the power supply section in positive and negative directions, so that the two helical coil elements 26 and 27 have a dipole structure. Can act as an antenna. Two helical coil elements are as if 2
This is almost equivalent to a diversity configuration transmitting and receiving with one antenna. The winding directions of the two helical coil elements 26 and 27 are the same. By using the built-in antenna device having the dipole configuration, a small amount of current does not flow through the ground plate metal in the housing or the housing itself, and the change in the radiation characteristics of the antenna due to handling by the hand of the mobile phone is small.

As shown in the embodiment of FIG. 5, by connecting the terminals 35, 36 of the two helical coil elements 32, 33 to independent power supply parts, the two helical coil elements 32,
33 acts as a diversity antenna.
In the case of the terminal arrangement of FIG. 5, two helical coils 32,
The winding direction of 33 is the same. The electrical length of the two helical coil elements 32 and 33 may be approximated to three-eighths of the target frequency in order to reduce the change in the radiation characteristics of the antenna and prevent the antenna impedance from becoming too large.

In order to cope with the widening of the transmission / reception target frequency and the multi-band handling of a plurality of widely separated target frequencies, it is easy to electromagnetically couple an additional element to two helical coil elements. Is effective in

FIG. 6 shows an example in which an additional element is used for a dipole antenna. FIG. 6A shows two helical coil elements 37, 3 having a dipole configuration.
8, a parasitic helical coil element 39 which is symmetrically bent with a common central axis is added. The winding diameter of the parasitic helical coil element 39 is two helical coil elements 37, 38.
The diameter may be smaller or the same diameter.

In FIG. 6B, a parasitic linear element 42 bent symmetrically near the center axis of the two helical coil elements 37 and 38 having the dipole structure is added.

The electric length of the additional parasitic helical coil element 39 or the linear element 42 is reduced to half of the target frequency, so that resonance occurs at the target frequency, and radio waves are received from the terminals 40 and 41 by electromagnetic coupling. And then transmit radio waves.

The electrical length of the helical coil element 39 or the linear element 42 without power supply is reduced to half the frequency slightly different from the target frequency of the two helical coil elements 37 and 38 having the dipole configuration. The target frequency can be broadened.

The electric length of the non-powered helical coil element 39 and the linear element 42 is reduced to one half of the high frequency greatly deviated from the target frequency of the two helical coil elements 37 and 38 of the dipole configuration. One target frequency can be handled.

FIG. 7 shows an embodiment in which an additional element is used for a diversity antenna. FIG.
In (a), two additional helical coil elements 45 and 46 having the same central axis as the two helical coil elements 43 and 44 of the diversity configuration are arranged, and connected independently to the terminals 47 and 48 to supply the power. And By making the electrical length correspond to the target frequency, it is possible to widen the band and cope with two target frequencies.

In FIG. 7B, an additional parasitic element 49 that is symmetrically bent is disposed near the central axis of the two helical coil elements 43 and 44 in the diversity configuration. When the electrical length of the parasitic element 47 is set to half the target frequency, resonance is likely to occur, and the terminal
Transmission and reception are possible from 7 and 48, and it is possible to cope with a wider band and two target frequencies.

When two helical coil elements are accommodated in the upper part of a miniaturized portable telephone, the two ends are inclined with respect to the vertical direction of the casing and cannot be accommodated in the width of the casing when the coil is normally wound. . Even if stored, the helical coil element is in a contracted state, and the efficiency as an antenna is reduced.
In order to avoid this, the dipole configuration shown in FIG.
The main winding surfaces of the two helical coil elements 50 and 51 and the two helical coil elements 54 and 55 having the diversity configuration shown in FIG. 8B are connected to the terminals 52 and 53 and the terminals 56 and 57, respectively. It is preferable that the end is parallel to the longitudinal center plane of the housing.

FIG. 8 shows two helical coil elements 58 and 59 from the top in order to avoid restrictions on the storage dimensions.
As shown in (c), it is preferable to shift the center axis and bring the inner end closer. By displacing the center axis, mutual interference between the antennas of the two helical coil elements 58 and 59 is reduced.

The electromagnetic shielding plate used in FIGS. 3, 4 and 5 is for reducing mutual interference between antennas of two adjacent helical coil elements, and is made of a material that absorbs or reflects electromagnetic waves. There is a need.

An electromagnetic shielding plate that absorbs and attenuates electromagnetic waves is considered to be the most excellent for shielding the built-in antenna of the present invention. 800 MHZ as the frequency used for mobile phones
From z to 1.9 GHz, it is necessary to efficiently absorb and attenuate in this band. As an example of a specific material,
Examples thereof include soft magnetic ferrite and fine powder thereof molded from rubber or resin, carbon, a molded metal wire having a fixed length, or a mixture of the above materials mixed at a fixed ratio.

To make the absorption of electromagnetic waves almost complete, the thickness needs to be about several mm or more. However, there is a limit in mobile phone applications where the shape and size and weight are restricted. As a countermeasure, it is conceivable to design with a certain level of attenuation or to add another configuration.

As another configuration, a plate of a conductive material such as a metal plate is laminated on a plate of a material that absorbs electromagnetic waves, and the electromagnetic waves that have not been absorbed or attenuated are reflected to further absorb the electromagnetic waves. Increase the efficiency of damping by passing through the layers of the board. In this case, in order to reduce the behavior of the plate made of a conductive material as an antenna, the plate may be electrically connected to a ground conductor such as a case metal in the mobile phone.

It is conceivable that the electromagnetic shielding plate is made of only a conductive material such as a metal plate. However, even if the electromagnetic shielding plate is sufficiently grounded, the antenna-like behavior cannot be eliminated. Therefore, the configuration of the electromagnetic shielding plate using only the metal plate is limited to the case where a certain effect is intended.

FIG. 10 shows the directional characteristics of the built-in antenna device of the present invention. FIG. 9 shows a measuring method, and FIG.
In the figure, a mobile phone 61 that houses a built-in antenna composed of two orthogonal helical coil elements 60 is arranged. An electromagnetic shielding plate 62 is arranged below the two helical coil elements 60, and a ground conductor 64 made of a plate-like metal plate is built in from the center to the bottom.

FIG. 9C shows a single helical coil element 6.
5 shows an arrangement in which a mobile phone 68 having an electromagnetic shielding plate 66 and a ground conductor 67 made of a metal plate is arranged below it.

FIG. 9B shows the measurement method three-dimensionally, and FIG. 10 shows the electric field intensity on the XY plane. A curve 69 shown by a thick solid line is a radiation pattern in the case of FIG. 9A, which is a built-in antenna composed of two orthogonal helical coil elements 60 of the present invention, and a curve 70 shown by a thin solid line is shown in FIG. 9 shows a radiation pattern in the case. In comparison, the difference in electric field strength in the X direction, that is, in the direction of the central axis of the single helical coil element 65 is large. The electrical length of the helical coil element was equivalent to 3/8 of the measurement frequency in each case.

Therefore, compared to using two helical coil elements having a single or parallel central axis as a built-in antenna device, the use of two helical coil elements whose central axes are orthogonal to each other is used as the built-in antenna device. Directivity characteristics can be obtained. As already described, a diversity effect can also be expected, which is naturally advantageous as a built-in antenna device of a mobile phone.

In FIG. 11, the voltage standing wave ratio (VSWR) of the built-in antenna device of the embodiment of FIG.
Is shown. The horizontal axis indicates the reception frequency, and the vertical axis indicates the VSWR. The closer the VSWR value is to 1.0, the more desirable the impedance is. There are regions where the VSWR is 2 or less in the frequency bands near 850 MHz and 1.9 GHz. By the way, the built-in antenna device is 850
A helical antenna element having an electrical length of 3/8 of the wavelength of MHz and 1.9 GHz was measured with the configuration shown in FIG.

[0054]

Since the present invention is configured as described above, it has the following effects.

Since the two helical coil elements are built in the upper part of the mobile phone, there is no protrusion of the antenna from the housing, which is excellent in portability and design.

Since there is no operation of pulling out or storing the antenna, the operation is simplified only by pressing the reception key during reception and the standby key during standby.

Since the two helical coil elements are substantially orthogonally housed in the upper part of the mobile phone, and the housing is configured such that the helical coil element is located close to the inside of the upper part, the space occupied by the built-in antenna device is relatively small. It becomes small and cohesive.

Even if two helical antennas and an electromagnetic shielding plate are used, the production is close to the production of a single component, and the cost is not higher than that of the conventional antenna.

The directional characteristics of the antenna are stable in almost any direction because the two helical coils are used orthogonally and the mutual interference is reduced.

Further, the two helical coil elements behave as two independent antennas. As a result, in the dipole configuration and the diversity configuration, in addition to a certain degree of spatial diversity, directional diversity and polarization diversity work effectively.

An electromagnetic shielding plate for reducing the interference between the antennas of the two helical coil elements is also provided continuously on the front side of the housing, so that the radiation of electromagnetic waves to the head during use of the mobile phone is suppressed. Is done.

By providing an additional helical coil element or a linear element with or without power supply to the two helical coil elements, it is relatively easy to widen the transmission and reception range and to achieve two frequencies.

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view of an embodiment of the present invention.

FIG. 2 is an external view of an embodiment of the present invention.

FIG. 3 is a partially cutaway perspective view of the embodiment of the present invention.

FIG. 4 is a partially cutaway perspective view of an embodiment of the present invention.

FIG. 5 is a partially cutaway perspective view of the embodiment of the present invention.

FIG. 6 is a configuration diagram of two helical coil elements of the present invention.

FIG. 7 is a configuration diagram of two helical coil elements of the present invention.

FIG. 8 is a configuration diagram of two helical coil elements of the present invention.

FIG. 9 is a diagram showing a measuring method according to an example of the present invention.

FIG. 10 is a diagram showing a radiation pattern of the built-in antenna device of the present invention.

FIG. 11 is a diagram showing a voltage standing wave ratio characteristic of the built-in antenna device of the present invention.

FIG. 12 is an external view showing an antenna of a conventional mobile phone.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Whip antenna 2 Helical antenna 3, 8, 15, 17 Housing 4, 19, 21 Receiving key 5, 20, 22 Standby key 6 Rod antenna 7 Inverted F type antenna 9, 10, 23, 24, 26, 27 , 32, 33, 3
7, 38, 43, 44, 50, 51, 54, 55, 5,
8, 59, 60, 65 Helical coil elements 11, 12, 30, 31, 35, 36, 40, 41, 4,
7, 48, 52, 53, 56, 57 Terminal 25, 28, 29, 34, 62, 66 Electromagnetic shielding plate 39 Bendless parasitic helical coil element 42, 49 Bend parasitic parasitic linear element 45, 46 Feed helical coil element

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04B 7/10 H04B 7/10 AB

Claims (19)

[Claims] 1. An antenna used in a mobile phone, wherein two elongated antenna elements are provided at an upper portion inside a housing so as to be substantially symmetrically inclined with respect to a longitudinal center plane of the housing.
A built-in antenna device, wherein a plurality of elongated antenna elements are arranged in an upward direction near the longitudinal center plane. 2. An antenna used in a portable telephone, wherein two helical coil elements are used as the two elongated antenna elements, and the central axes of the two helical coil elements are substantially orthogonal to each other. The built-in antenna device according to claim 1, wherein: 3. The built-in antenna device according to claim 2, wherein in the antenna used for the mobile phone, the two helical coil elements are provided with positive and negative power supply portions to form a dipole configuration. 4. The built-in antenna device according to claim 2, wherein in the antenna used in the portable telephone, the two helical coil elements are provided with independent power supply portions to form a diversity configuration. 5. An antenna used in a mobile phone, wherein an electromagnetic shielding plate is arranged near the longitudinal center plane of the two helical coil elements and perpendicular to the front surface of the housing. The built-in antenna device according to claim 2. 6. An antenna used in a mobile phone, wherein an electromagnetic shielding plate is arranged below said two helical coil elements.
The antenna device as described in the above. 7. An antenna used in a portable telephone, wherein a continuous electromagnetic shielding plate is arranged from a lower part of said two helical coil elements to a front side of said casing. 5. The built-in antenna device according to 4. 8. The built-in antenna device according to claim 5, wherein said electromagnetic shielding plate is made of a radio wave absorbing material in an antenna used for a portable telephone. 9. An antenna used in a mobile phone, wherein a plate obtained by laminating a radio wave absorbing material and a conductive material is used as the electromagnetic shielding plate, and the radio wave absorbing material is arranged on the two helical coil element sides. The built-in antenna device according to claim 5, 6, or 7, wherein: 10. The built-in antenna device according to claim 9, wherein said conductive material of said stacked plates is electrically connected to a ground conductor in said housing. 11. An antenna used in a portable telephone, wherein an additional parasitic helical coil element which is symmetrically bent with a common central axis of said two helical coil elements of said dipole configuration is arranged. The built-in antenna device according to claim 3. 12. An antenna used in a portable telephone, wherein an additional parasitic wire element symmetrically bent is disposed near a center axis of the two helical coil elements in the dipole configuration. 3. The built-in antenna device according to 3. 13. An antenna used in a mobile phone, wherein an additional parasitic wire element symmetrically bent is disposed near a center axis of the two helical coil elements in the diversity configuration. 5. The built-in antenna device according to 4. 14. An antenna used in a mobile phone, wherein two additional helical coil elements are provided with a common central axis of said two helical coil elements in said diversity configuration, and are connected to said independent feeder. The built-in antenna device according to claim 4, wherein: 15. An antenna used in a mobile phone, wherein said two helical coil elements are housed in an upper portion of said housing, and a central portion of said upper portion of said housing is continuously convex. The built-in antenna device according to claim 2, wherein: 16. An antenna used in a portable telephone, wherein an electric length of the symmetrically bent parasitic helical coil element is set to a half of a wavelength of a target frequency. Built-in antenna device. 17. An antenna used for a portable telephone, wherein an electric length of the symmetrically bent parasitic element is set to a half of a wavelength of a target frequency. A built-in antenna device as described. 18. An antenna used in a mobile phone, wherein main winding surfaces of the two helical coil elements are parallel to the longitudinal center plane of the housing. Built-in antenna device. 19. An antenna used in a portable telephone, wherein the central axes of said two helical coil elements are shifted in the front-rear direction of said housing.
A built-in antenna device as described.