JP2001119222A - Small radio - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the degradation of antenna performance by appropriately adjusting the impedance of an unselected antenna in a diversity reception system. SOLUTION: This small radio equipment, which has a whip antenna 11 for both transmission and reception and a built-in antenna 12 for diversity reception and which selects either of them by an antenna changeover switch 15, connects the antenna 12 to an impedance adjustment circuit 21 by a 2nd antenna receiving switch 18 included in the switch 15 that also operates as an impedance changeover switch 20 when the switch 15 selects the antenna 11, appropriately adjusts the impedance of the antenna 12 by connecting the antenna 12 to the ground of the equipment main body through the circuit 21 and makes a high frequency current flow to the unselected antenna 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small radio having an antenna of a diversity receiving system.

[0002]

2. Description of the Related Art In a conventional small wireless device such as a cellular phone,
As a countermeasure against fading in which the signal strength fluctuates periodically, a diversity receiving system is used. For example,
The antenna switching method that uses a whip antenna that can be stored in the main body of the radio and a built-in antenna for diversity reception has the advantage that only one system is required for the reception circuit compared to the diversity of the combined reception type. In order to meet the demand for smaller and thinner devices, antenna switching diversity is mainly used in small wireless devices.

FIG. 5 is an overall perspective view of a conventional small radio, and FIG. 6 is a side view of the small radio shown in FIG. The whip antenna 51 shown in each figure is a main antenna for both transmission and reception, and is generally located on the upper part of the wireless device main body 55 and the like. The built-in antenna (a flat antenna or the like) 52 is used as a sub-antenna dedicated to diversity reception, and is generally located on the opposite side of the receiver 56 so as not to be covered with the hand.

FIG. 7 is a block diagram showing the configuration of the conventional small radio shown in FIGS. 5 and 6. The whip antenna 51 is connected to a wireless circuit 64 via an antenna matching circuit 61 and an antenna switch 63. Similarly, the built-in antenna 52 is connected to a wireless circuit 64 via an antenna matching circuit 62 and an antenna switch 63. 800MHz for mobile phone systems in Japan
Band and PDC (Pers
Onal Digital Cellular) system is common, and the diversity reception of the antenna switching system is performed by using two antennas of the main whip antenna 51 and the sub built-in antenna 52 as described above. At the time of reception, the whip antenna 51 and the built-in antenna 52 select the antenna output with the higher received electric field strength by switching the antenna switch 63. The antenna switching by the antenna switch 63 is controlled by the control circuit 65 of the wireless circuit 64.
Such diversity reception enables high-quality and stable mobile communication.

[0005]

In the above conventional example, when transmission or reception is performed by the whip antenna 51, a high-frequency current having a transmission or reception frequency flows through the whip antenna 51. At this time, the built-in antenna 52 is connected to the wireless circuit 64
, No high-frequency current flows. However, the high-frequency current at the time of transmission / reception by the whip antenna 51 is not limited to the whip antenna 51, and also includes reflection / leakage via the feed line 53 such as a spring shown in FIGS. Will flow throughout.

Therefore, as shown in FIG. 8 in a state of use, a person holds the wireless device main body 55 by hand 71 and
When the whip antenna 51 is used with the
When transmitting or receiving the data, the radio frequency current flowing through the substrate 54 is covered with the hand 71 to shield the ground plane of the antenna, so that the antenna performance is deteriorated and the communication quality is deteriorated. There was a problem. Further, in order to reduce the size of the wireless device main body 55, it is desired that the antenna changeover switch 63 and the like be configured as small as possible to reduce the installation space.

[0007] The present invention has been made in view of the above circumstances, and in a diversity receiving system, a small radio device capable of appropriately adjusting the impedance of an unselected antenna and preventing deterioration of antenna performance. The purpose is to provide.

[0008]

According to the present invention, there is provided a small radio, comprising: a first antenna for transmission / reception, a second antenna for diversity reception, and antenna switching means for selectively switching between the first antenna and the second antenna. A second antenna impedance adjustment circuit that adjusts the impedance of the second antenna; and a second antenna that is provided integrally with the antenna switching unit and that switches connection between the second antenna and the second antenna impedance adjustment circuit. Antenna impedance switching means, and an impedance for connecting the second antenna and the second antenna impedance adjustment circuit to allow a high-frequency current to flow through the second antenna when the antenna switching means selects the first antenna. Adjustment control means.

[0009] Preferably, the second antenna impedance switching means includes a second antenna for connecting the second antenna to one of the radio circuit side and the second antenna impedance adjusting circuit, and for performing both antenna switching and impedance switching. And a changeover switch.

Preferably, the impedance adjustment control means connects the second antenna and the second antenna impedance adjustment circuit when the antenna switching means selects the first antenna during transmission. A high-frequency current is caused to flow through the second antenna.

Alternatively, the impedance adjustment control means connects the second antenna with the second antenna impedance adjustment circuit when the antenna switching means selects the first antenna at the time of reception, and controls the high-frequency current To the second antenna.

Alternatively, the second antenna impedance adjustment circuit includes a transmission adjustment circuit adapted to a transmission frequency;
A reception adjustment circuit adapted to a reception frequency, wherein the impedance adjustment control unit is configured to transmit the second antenna and the transmission adjustment circuit when the antenna switching unit selects the first antenna during transmission. And the high-frequency current is supplied to the second antenna, and the second antenna is connected to the reception adjustment circuit when the antenna switching unit is selecting the first antenna during reception. A high-frequency current flows through the second antenna.

Preferably, a first antenna impedance adjusting circuit for adjusting the impedance of the first antenna is provided integrally with the antenna switching means,
A first antenna impedance switching unit for switching connection between the first antenna and the first antenna impedance adjustment circuit, wherein the impedance adjustment control unit selects the second antenna when receiving the signal; In this case, the first antenna and the first antenna impedance adjusting circuit are connected to allow a high-frequency current to flow through the first antenna.

In the above configuration, when transmitting or receiving,
Alternatively, when the first antenna is selected by the antenna switching unit during transmission / reception, the second antenna not selected and the second antenna impedance adjustment circuit are connected to appropriately adjust the impedance of the second antenna. Accordingly, a high-frequency current flows to the second antenna. Also, when the second antenna is selected by the antenna switching means during reception by diversity, the first antenna not selected and the first antenna impedance adjustment circuit are connected to appropriately adjust the impedance on the first antenna side. The adjustment allows a high frequency current to flow through the first antenna. Thereby, the impedance of the unselected antenna is adjusted to an appropriate value in accordance with the antenna selection state at the time of transmission or reception, respectively, so that high-frequency current is prevented from flowing to the substrate of the wireless device body or the like. In addition, deterioration of antenna performance is reduced.

As the second antenna impedance switching means, a second antenna changeover switch which performs both antenna switching and impedance switching for connecting the second antenna to either the radio circuit side or the second antenna impedance adjusting circuit is used. With this configuration, the impedance switching means can be incorporated in the antenna switching means, so that the circuit of the switch portion of the switching means can be simplified and downsized, and the device can be downsized and thinned.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. [First Embodiment] FIG. 1 is a block diagram showing a configuration of a small wireless device according to a first embodiment of the present invention, and FIG. 2 is a state in which a person uses the small wireless device of the present embodiment in his hand. FIG.

The small wireless device of this embodiment has a whip antenna 11 as a first antenna serving as a transmitting / receiving main antenna and a built-in antenna 12 serving as a second antenna serving as a sub-antenna dedicated to diversity reception. The whip antenna 11 can be housed inside the wireless device main body, for example, and is provided so as to extend and contract from the main body when used. The first antenna is not limited to the whip antenna, and a helical antenna or the like can be used. The built-in antenna 12 is composed of a flat antenna or the like,
The whip antenna 11 is provided on the upper side of the wireless device main body.

The whip antenna 11 is connected to a radio circuit 19 via an antenna matching circuit 13 and an antenna switch 15. The built-in antenna 12 is connected to a radio circuit 19 via an antenna matching circuit 14 and an impedance changeover switch circuit 20 in the antenna changeover switch 15.
It is connected to the. The antenna changeover switch 15 corresponding to the antenna changeover means is configured by a group of switches for switching between the whip antenna 11 and the built-in antenna 12 in accordance with the operation of transmission and reception (diversity reception) by the wireless circuit 19. This antenna changeover switch 15
Are the first antenna transmission switch 16 and the first antenna reception switch 17 for switching the whip antenna 11.
And a second antenna reception switch 18 corresponding to a second antenna switch for switching the built-in antenna 12.

The second antenna receiving switch 18 also serves as an impedance changeover switch circuit 20.
The antenna matching circuit 14 is connected to the common terminal, the radio circuit 19 and the impedance adjustment circuit 21 are connected to the respective selection terminals, and the built-in antenna 12 is switched to the radio circuit 19 or the impedance adjustment circuit 21 for connection. That is, the antenna changeover switch 15 has a configuration in which the impedance changeover switch circuit 20 corresponding to the second antenna impedance changeover means is incorporated. The impedance adjustment circuit 21 corresponding to the second antenna impedance adjustment circuit is configured by an LC circuit or the like, and is a circuit for adjusting the impedance when the built-in antenna 12 is not selected, and the terminal is connected to the ground of the wireless device main body. . Note that if the receiving system using the built-in antenna 12 is matched once with an input / output impedance of 50Ω, the deviation is not as severe as that of the transmitting system, so the antenna matching circuit 14 may be omitted.

The radio circuit 19 includes a transmission circuit 24, a reception circuit 25, a frequency circuit 26, and a control circuit 23. The transmission circuit 24 includes a modulation unit, a transmission mixer, a transmission power amplification unit, and the like. The receiving circuit 25 includes a high-frequency amplifier, a reception mixer, an intermediate frequency amplifier, a demodulator, and the like. The frequency circuit 26 generates a frequency signal for frequency conversion in the transmission mixer and the reception mixer, and includes a temperature-compensated crystal oscillator (TCXO), a frequency synthesizer having a VCO, and the like.
The control circuit 23 corresponds to impedance adjustment control means, includes a baseband circuit for performing encoding / decoding of an audio signal, and controls overall transmission / reception operations, switching timing control of each switch of the antenna switching switch 15, and the like. And an MPU or DSP that performs the above.

Next, the operation of this embodiment will be described. The antenna switch 15 switches the connection between the whip antenna 11 and the built-in antenna 12 based on a switching control signal from the control circuit 23. In this embodiment,
1 illustrates a small wireless device of a PDC system that performs wireless communication of a TDMA system.

The antenna switch 15 includes a first antenna transmission switch 16 and a first antenna reception switch 1.
7, the connection of the whip antenna 11 is transmitted at a predetermined timing and at a constant cycle by the transmission circuit 24 or the reception circuit 25.
, The transmission and reception are switched, and the whip antenna 11 is shared for transmission and reception. Also, the first
Diversity reception is performed by selecting and switching between the whip antenna 11 and the built-in antenna 12 with the higher reception electric field strength by the antenna reception switch 17 and the second antenna reception switch 18.

The first embodiment describes in detail the impedance adjustment operation of the unselected internal antenna 12 at the time of transmission by the whip antenna 11. When transmission is performed by the whip antenna 11, in the antenna switch 15, the first antenna transmission switch 16 is turned on (conduction state), the first antenna reception switch 17 is turned off (non-conduction state), and the second antenna reception switch 18 is turned on. Is switched to the impedance adjustment circuit 21 side. As a result, the whip antenna 11 is
, The built-in antenna 12 is connected to the ground of the radio unit via the impedance adjustment circuit 21, and is separated from the receiving circuit 25.

In this case, the second antenna reception switch 18 also serving as the impedance changeover switch circuit 20 is switched in conjunction with the first antenna transmission switch 16 based on a switching control signal from the control circuit 23. That is, when the first antenna transmission switch 16 is on,
Antenna receiving switch 18 is impedance adjustment circuit 2
When the first antenna transmission switch 16 is off, the second antenna reception switch 18 is connected to the radio circuit 19. When the impedance adjustment circuit 21 is connected to the built-in antenna 12, the impedance when the built-in antenna 12 side is viewed from the connection point (the ground side of the impedance adjustment circuit 21) 22 in FIG. Set as follows.

As described above, at the time of transmission by the whip antenna 11, the built-in antenna 12 is connected to the impedance adjustment circuit 21 by the second antenna reception switch 18, and the terminal is terminated via the impedance adjustment circuit 21 to the ground of the radio main unit. Connected to. For this reason, as shown in FIG. 2, unnecessary high-frequency currents at the time of transmission, such as current components reflected back without being radiated by the antenna at high-frequency currents of the transmission frequency flowing through the whip antenna 11, are transmitted by the antenna switch 15. Hardly flows to the substrate 33 on which the wireless circuit 19 and the like are mounted, flows to the built-in antenna 12, and is radiated as heat.

As shown in FIG. 2, the built-in antenna 12 is mounted on the radio body 31 so that the radio body 31 is not covered with the hand 34 while the person is holding the radio body 31 with the hand 34 during use. It is located above a portion opposite to the receiver 32 with the substrate 33 interposed therebetween. Therefore, whip antenna 1
Since the high-frequency current flows to the built-in antenna 12 side and hardly flows to the substrate 33 at the time of transmission by 1, the high-frequency current does not fluctuate due to the influence of the hand 34, and deterioration of the antenna performance is minimized. .

As described above, according to the present embodiment, the impedance of the built-in antenna 12 can be adjusted to an appropriate value at the time of transmission by the whip antenna 11, and unnecessary high-frequency current can flow through the built-in antenna 12. This allows
It is possible to prevent the antenna performance from deteriorating when a person is holding it with his / her hand, to maximize the use of the antenna in accordance with the selected state of the antenna, and to improve the communication quality. Further, an impedance changeover switch circuit 2
By incorporating “0” into the antenna change-over switch 15 also as the second antenna receiving switch 18, the circuit of the switch portion can be simplified and downsized, and the device can be further downsized and thinned. . Also, in this case,
Since the number of connection paths is reduced, insertion loss can be reduced, and the antenna performance can be further improved.

[Second Embodiment] FIG. 3 is a block diagram showing a configuration of a small wireless device according to a second embodiment of the present invention.
The second embodiment describes in detail the impedance adjustment operation of the unselected internal antenna 12 at the time of reception by the whip antenna 11. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

The antenna changeover switch 35 serves as a first antenna transmission switch 16 and a first antenna reception switch 17 for switching the whip antenna 11 and a second antenna reception switch circuit 20 serving as an impedance changeover switch circuit 20 for switching the built-in antenna 12. It has a switch 18 and an impedance switch 38 for switching the impedance of the whip antenna 11. An impedance adjustment circuit 36 for adjusting the impedance when the built-in antenna 12 is not selected is connected to one selected terminal of the second antenna reception switch 18, and the terminal is connected to the ground of the radio unit. Impedance adjustment circuit 3
Reference numeral 6 denotes a connection point in FIG. 3 when connected to the built-in antenna 12 (the ground side of the impedance adjustment circuit 36).
The impedance when looking at the built-in antenna 12 side from 37 is
It is set so as to be 50Ω at the reception frequency.

The impedance changeover switch 38
Is connected to an impedance adjustment circuit 39 for adjusting the impedance when the whip antenna 11 is not selected.
The end is connected to the ground of the radio. When the impedance adjustment circuit 39 is connected to the whip antenna 11, the impedance when the whip antenna 11 side is viewed from the connection point (the ground side of the impedance adjustment circuit 39) 40 in FIG. Set it.

Next, the operation of this embodiment will be described. In general antenna switching type diversity reception, the whip antenna 11 and the built-in antenna 12 are arranged at a predetermined distance based on the reception wavelength, and the antenna with the higher reception electric field strength is selected from the two antennas. Second
In the embodiment, an operation when the whip antenna 11 is selected in the diversity reception will be described.

When receiving with the whip antenna 11,
In the antenna switch 35, the first antenna transmission switch 16 is turned off, and the first antenna reception switch 1 is turned off.
7 is turned on, the second antenna reception switch 18 is turned to the impedance adjustment circuit 36 side, and the impedance changeover switch 38 is turned off. Thus, the whip antenna 11 is connected to the receiving circuit 25, and the built-in antenna 12
Is connected to the ground of the radio unit via an impedance adjusting circuit 36 and is separated from the receiving circuit 25.

In this case, the second antenna reception switch 18 also serving as the impedance switching switch circuit 20 is switched in conjunction with the first antenna reception switch 17 based on a switching control signal from the control circuit 23. That is, when the first antenna reception switch 17 is on,
The antenna receiving switch 18 is the impedance adjustment circuit 3
On the other hand, when the first antenna reception switch 17 is off, the second antenna reception switch 18 is connected to the radio circuit 19.

As described above, at the time of reception by the whip antenna 11, the built-in antenna 12 is connected to the impedance adjustment circuit 36 by the second antenna reception switch 18, and the terminal is terminated via the impedance adjustment circuit 36 to the ground of the radio body. Connected to. For this reason, as in the case of the transmission shown in FIG. 2, unnecessary high-frequency current such as in the vicinity of the reception frequency at the time of reception hardly flows to the substrate 33 on which the antenna changeover switch 35 and the radio circuit 19 are mounted. Flows toward the built-in antenna 12 and is radiated as heat. Therefore, at the time of reception by the whip antenna 11, the high-frequency current flows to the built-in antenna 12 side and hardly flows to the substrate 33.
4 does not fluctuate under the influence of (4), and deterioration of antenna performance is minimized.

As described above, according to the present embodiment, the impedance of the built-in antenna 12 can be adjusted to an appropriate value at the time of reception by the whip antenna 11, and unnecessary high-frequency current can flow through the built-in antenna 12. This allows
It is possible to prevent the antenna performance from deteriorating when a person is holding it with his / her hand, to maximize the use of the antenna in accordance with the selected state of the antenna, and to improve the communication quality.

[Third Embodiment] FIG. 4 is a block diagram showing a configuration of a small radio device according to a third embodiment of the present invention.
The third embodiment describes in detail the impedance adjustment operation of an unselected antenna during transmission / reception with the whip antenna 11 or reception with the built-in antenna 12. The same components as those in the first and second embodiments are denoted by the same reference numerals, and description thereof is omitted.

The antenna switch 41 is a first antenna transmitting switch 16 and a first antenna receiving switch 17 for switching the whip antenna 11 and a second antenna receiving switch circuit 42 for switching the impedance of the built-in antenna 12. A switch 43 and an impedance changeover switch 38 corresponding to first antenna impedance changeover means for changing over the impedance of the whip antenna 11 are provided. The selection terminal of the second antenna reception switch 43 includes a radio circuit 19, an impedance adjustment circuit 21 corresponding to a transmission adjustment circuit for adjusting the impedance of the built-in antenna 12 at the time of transmission of the whip antenna 11, And an impedance adjustment circuit 36 corresponding to a reception adjustment circuit for adjusting the impedance of the built-in antenna 12.

The impedance adjustment circuit 21 controls the impedance adjustment circuit 3 so that the impedance seen from the connection point 22 toward the built-in antenna 12 when connected to the built-in antenna 12 becomes 50Ω at the transmission frequency.
6 is a connection point 37 when connected to the built-in antenna 12.
Is set so that the impedance when looking at the built-in antenna 12 side becomes 50Ω at the reception frequency.

The impedance changeover switch 38
Has a built-in antenna 12 and a whip antenna 11 at the time of reception.
The impedance adjustment circuit 39 corresponding to the first antenna impedance adjustment circuit for adjusting the impedance of the wireless communication device is connected, and the terminal end is connected to the ground of the wireless device main body.
The impedance adjustment circuit 39 includes the whip antenna 11
When connected to the whip antenna 1 from the connection point 40
The impedance seen from one side is 50 at the reception frequency.
Set to Ω.

Next, the operation of this embodiment will be described. First, an operation at the time of transmission by the whip antenna 11 will be described. When transmitting with the whip antenna 11, in the antenna changeover switch 41, the first antenna transmission switch 16 is turned on, the first antenna reception switch 17 is turned off, and the second antenna reception switch 43 is placed on the impedance adjustment circuit 21 side. The changeover switch 38 is turned off. As a result, the whip antenna 11 is connected to the transmission circuit 24, the built-in antenna 12 is connected to the ground of the radio unit via the impedance adjustment circuit 21, and is separated from the reception circuit 25.

Next, the operation when the whip antenna 11 is selected in the diversity reception will be described. When receiving with the whip antenna 11, the first antenna transmission switch 16
Is turned off, the first antenna reception switch 17 is turned on, the second antenna reception switch 43 is turned to the impedance adjustment circuit 36 side, and the impedance changeover switch 38 is turned off. As a result, the whip antenna 11 is connected to the receiving circuit 25, and the built-in antenna 12 is connected to the ground of the radio unit via the impedance adjusting circuit 36, and is separated from the receiving circuit 25.

Next, the operation when the built-in antenna 12 is selected in the diversity reception will be described. When receiving with the built-in antenna 12, the antenna switch 41 turns off the first antenna transmission switch 16, turns off the first antenna reception switch 17, and switches the second antenna reception switch 43 to the radio circuit 19 side. The switch 38 is turned on. As a result, the built-in antenna 12 is connected to the receiving circuit 25, the whip antenna 11 is connected to the ground of the radio unit via the impedance adjusting circuit 39, and is separated from the transmitting circuit 24 and the receiving circuit 25.

In this case, the second antenna reception switch 43 also serving as the impedance changeover switch circuit 42 and the impedance changeover switch 38 are connected to the first antenna transmission switch 1 based on the changeover control signal from the control circuit 23.
6 and the first antenna reception switch 17. That is, when the first antenna transmission switch 16 is on, the second antenna reception switch 43 is connected to the impedance adjustment circuit 21 side by the first antenna reception switch 1.
When the switch 7 is on, the second antenna reception switch 43 is connected to the impedance adjustment circuit 36 side. When the second antenna reception switch 43 is connected to the wireless circuit 19, the impedance changeover switch 38 is turned on to connect to the impedance adjustment circuit 39.

As described above, at the time of transmission by the whip antenna 11, the built-in antenna 12 is connected to the impedance adjustment circuit 21 by the second antenna reception switch 43. Connected to. Further, at the time of reception by the whip antenna 11, the built-in antenna 12 is connected to the impedance adjustment circuit 36 by the second antenna reception switch 43, and the impedance adjustment circuit 3
The terminal is connected to the ground of the radio unit via the terminal 6. Further, at the time of reception by the built-in antenna 12, the whip antenna 11 is connected to an impedance adjustment circuit 39 by an impedance changeover switch 38, and the terminal is connected to the ground of the wireless device main body via the impedance adjustment circuit 39.

For this reason, unnecessary high-frequency currents during transmission and reception hardly flow to the substrate 33 on which the antenna changeover switch 41 and the radio circuit 19 are mounted, as in the case shown in FIG. At the time of transmission / reception by the antenna 11, it flows toward the built-in antenna 12, and at the time of reception by the built-in antenna 12, it flows toward the whip antenna 11 and is radiated as heat. Therefore, the high-frequency current hardly flows through the substrate 33 during transmission / reception, so that the high-frequency current does not fluctuate due to the influence of the hand 34, and deterioration of the antenna performance is minimized.

As described above, according to the present embodiment, in each state of transmission and reception by the whip antenna 11 and reception by the built-in antenna 12, by appropriately switching and connecting the three systems of impedance adjustment circuits, Even in a proper antenna selection state, the impedance of the unselected antenna can be adjusted to an appropriate value, and unnecessary high-frequency current can flow to the non-selected antenna. This prevents deterioration of antenna performance when a person is holding it by hand in both transmission and diversity reception, and maximizes the antenna's capabilities according to the antenna selection state. Therefore, the effect of improving communication quality and enabling high-quality and stable mobile communication can be obtained.

[0047]

As described above, according to the present invention, in the diversity receiving system, the antenna switching means is the first type.
When the antenna is selected, the second antenna impedance switching means connects the second antenna and the second antenna impedance adjustment circuit to cause a high-frequency current to flow through the second antenna, thereby reducing the impedance of the unselected antenna. There is an effect that adjustment can be appropriately performed and deterioration of antenna performance can be prevented.

The second antenna impedance switching means has a second antenna changeover switch for performing both antenna switching and impedance switching for connecting the second antenna to either the radio circuit side or the second antenna impedance adjustment circuit. With this configuration, the circuit of the switch portion of the switching unit can be simplified and downsized,
There is an effect that the size of the device can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a small wireless device according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram illustrating a state in which a person uses the small wireless device of the present embodiment while holding the wireless device.

FIG. 3 is a block diagram illustrating a configuration of a small wireless device according to a second embodiment of the present invention.

FIG. 4 is a block diagram illustrating a configuration of a small wireless device according to a third embodiment of the present invention.

FIG. 5 is an overall perspective view of a conventional small wireless device.

FIG. 6 is a side view of the small wireless device shown in FIG. 5;

FIG. 7 is a block diagram showing a configuration of a conventional small wireless device.

8 is an explanatory diagram showing a state in which a person uses the conventional small wireless device shown in FIG. 6 while holding it.

[Explanation of symbols]

 Reference Signs List 11 whip antenna 12 built-in antenna 13, 14 antenna matching circuit 15, 35, 41 antenna changeover switch 16 first antenna transmission switch 17 first antenna reception switch 18 second antenna reception switch 19 radio circuit 20 impedance changeover switch circuit 21, 36, 39 impedance adjustment circuit 22, 37, 40 connection point 23 control circuit 24 transmission circuit 25 reception circuit 26 frequency circuit 31 radio body 32 receiver 33 substrate 34 hand

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04B 7/26 H04B 7/26 D (72) Inventor Yoshio Koyanagi 4--3 Tsunashima Higashi, Kohoku-ku, Yokohama-shi, Kanagawa Prefecture No. 1 Inside Matsushita Communication Industrial Co., Ltd. (72) Inventor Masaomi Nishinomaki 3-1-1 Tsunashima Higashi, Kohoku-ku, Yokohama, Kanagawa Prefecture Inside (72) Inventor Kenichi Yamada Tsunashima, Kohoku-ku, Yokohama, Kanagawa Prefecture No. 4-1, Higashi 4-chome F-term in Matsushita Communication Industrial Co., Ltd. (reference) 5J021 AA02 AA13 AB03 AB06 CA01 CA06 DB04 FA20 FA24 FA26 FA31 FA32 GA01 HA05 HA10 JA02 5J047 AA03 AA07 AB06 AB10 FA09 5K059 CC03 DD02 DD27 5K067 AA02 BB04 CC DD51 EE02 EE10 KK03

Claims (6)

[Claims] A first antenna for transmission / reception, a second antenna for diversity reception, an antenna switching means for selectively switching between the first antenna and the second antenna, and a first antenna for adjusting an impedance of the second antenna. A second antenna impedance adjustment circuit, a second antenna impedance switching unit that is provided integrally with the antenna switching unit, and switches connection between the second antenna and the second antenna impedance adjustment circuit; Impedance selecting control means for connecting the second antenna and the second antenna impedance adjusting circuit to allow a high-frequency current to flow through the second antenna when the first antenna is selected. Small radio. 2. The second antenna impedance switching means, comprising: a second antenna changeover switch that performs both antenna switching and impedance switching for connecting the second antenna to either a radio circuit side or the second antenna impedance adjustment circuit. 2. The small wireless device according to claim 1, comprising: 3. The impedance adjustment control means connects the second antenna and the second antenna impedance adjustment circuit when the antenna switching means selects the first antenna during transmission, and controls the high frequency current. 3. The small wireless device according to claim 1, wherein the second radio is supplied to the second antenna. 4. The radio communication apparatus according to claim 1, wherein said impedance adjustment control means connects said second antenna and said second antenna impedance adjustment circuit when said antenna switching means selects said first antenna at the time of reception. 3. The small wireless device according to claim 1, wherein the second radio is supplied to the second antenna. 5. The second antenna impedance adjustment circuit includes a transmission adjustment circuit adapted to a transmission frequency, and a reception adjustment circuit adapted to a reception frequency, wherein the impedance adjustment control means is configured to transmit the antenna at the time of transmission. When the switching means is selecting the first antenna, the second antenna is connected to the adjustment circuit for transmission so that a high-frequency current flows through the second antenna. 3. The small radio device according to claim 1, wherein when one antenna is selected, the second antenna is connected to the reception adjustment circuit to pass a high-frequency current to the second antenna. 6. A first antenna impedance adjustment circuit that adjusts the impedance of the first antenna, and is provided integrally with the antenna switching means, and switches connection between the first antenna and the first antenna impedance adjustment circuit. A first antenna impedance switching unit that performs the first antenna impedance adjustment circuit when the antenna switching unit selects the second antenna during reception. The small wireless device according to any one of claims 1 to 5, wherein a high-frequency current flows through the first antenna by connecting the first antenna and the second antenna.