JPH11150496A - Antenna system and portable radio equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an antenna system that is capable of good diversity reception. SOLUTION: This proposed system has a first and a second antennas 2, 3 and a selector switch 4 that selects either of the first and second antennas 2, 3 and conducts diversity reception by using the selector switch 4 to select any desired antenna from the first and second antennas 2, 3. A phase shift circuit 11 that delays the phase of a received signal by a desired value is provided between the first antenna 2, and the selector switch 4 or between the second antenna 3 and the switch 4. In this way, since the phase of a signal sent from the antenna during non-selection can be adjusted, cancellation of the received signal by the this signal is prevented. As a result, further improved diversity reception is realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[Table of Contents] The present invention will be described in the following order.

BACKGROUND OF THE INVENTION Prior Art (FIG. 6) Problems to be Solved by the Invention Means for Solving the Problems Embodiments of the Invention (1) First Embodiment (FIGS. 1 and 2) (2) Second Embodiment (FIG. 3) (3) Third Embodiment (FIG. 4) (4) Other Embodiments (FIG. 5) Effects of the Invention

[0003]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna device and a portable wireless device, and is suitably applied to a small wireless device such as a portable telephone.

[0004]

2. Description of the Related Art Conventionally, in such a small-sized radio device, two antennas are provided as receiving antennas, and so-called diversity reception in which an antenna having a better reception state is selected from the two antennas and received is selected. In some cases, it is possible to suppress the fading caused by the multiplex wave and perform good communication. In fact, even in Japan, PDC (Personal D
In a digital cellular phone called an "igital Cellular" system, a whip antenna is attached to the main body so that it can be pulled out and stored, and a built-in antenna such as a planar antenna is mounted inside the main body, and these two antennas are used. Diversity reception is performed.

Here, a receiver for performing such diversity reception will be specifically described with reference to FIG. As shown in FIG. 6, a receiver 1 for performing diversity reception is roughly divided into first and second antennas 2 and 3, a selection switch 4 for selecting these two antennas 2, 3, and a selection switch 4. Received signal S1 obtained by selecting operation of switch 4
Circuit 5 that performs predetermined demodulation processing on the received data to obtain received data
It is composed of

In this case, the first antenna 2 is composed of a whip antenna which is attached to the main body of the wireless device on which the receiver 1 is mounted so that it can be pulled out and stored, and the second antenna is attached to the main body. It has a built-in antenna that is stored. Also, the first and second antennas 2, 3
Are connected to the first and second input terminals a and b of the selection switch 4 via matching circuits 6 and 7 for impedance matching, respectively. The selection switch 4 is connected to the input terminals a, a based on the switching control signal S2 from the receiving circuit 5.
By connecting one of the signals b to the output terminal c, the reception signal having the higher signal level among the reception signals received by the first and second antennas 2 and 3 is output to the reception circuit 5 as the reception signal S1. I do.

The receiving circuit 5 outputs the switching control signal S1 to the selection switch 4 as appropriate to cause the selection switch 4 to perform the selection operation, and always determines the signal level of the resultant reception signal S1 by determining the signal level. The selection switch 4 selects the higher-level antenna. Thus, the receiving circuit 5 performs a demodulating process on the received signal S1 obtained by such a selecting operation, thereby performing a receiving operation in which the influence of fading is avoided, and receiving data transmitted from the transmitting side. Can be accurately restored.

[0008]

However, when the receiver 1 having such a configuration is mounted on a small portable radio, the first
Since the distance between the first and second antennas 2 and 3 cannot be sufficiently ensured, the first and second antennas 2 and 3 are spatially coupled with each other, and as a result, the unselected antenna May adversely affect the selected antenna, which may cause some inconvenience. Specifically, when in the selected state as shown in FIG. 6, the received signal received by the antenna (2) which is not selected is reflected at the open end (a), and the reflected received signal is reflected. Is radiated from the antenna (2), and this wraps around to the antenna (3). As a result, this signal degrades the signal level of a received signal that should be received by the antenna (3), and good diversity reception is achieved. If you can't do that, you will have problems.

The present invention has been made in view of the above points, and has as its object to propose an antenna device and a portable radio device capable of performing diversity reception better than before.

[0010]

In order to solve the above-mentioned problems, the present invention provides a first and a second antenna, and a first and a second antennas.
And a selecting means for selecting any one of the second and second antennas. The antenna apparatus is configured to perform diversity reception by selecting a desired first or second antenna by the selecting means. In the above, the phase delay means for delaying the phase of the received signal by a desired amount is provided between the first antenna and the selection means and / or between the second antenna and the selection means.

In the present invention, there are provided first and second antennas, and a selecting means for selecting one of the first and second antennas. Or in a portable wireless device having an antenna device adapted to perform diversity reception by selecting the second antenna, between the first antenna and the selection means, and or between the second antenna and the selection means, Phase delay means for delaying the phase of the received signal by a desired amount is provided.

If a desired amount of phase delay is applied to the received signal by the phase delay means, the phase of the signal transmitted from the antenna can be adjusted when the signal is not selected, so that the signal can be prevented from canceling out the received signal. I can do it.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

(1) First Embodiment In FIG. 1 in which parts corresponding to those in FIG. 6 are assigned the same reference numerals, reference numeral 10 denotes a receiver for performing diversity reception to which the present invention is applied as a whole. Matching circuit 6 for antenna 2
In the subsequent stage, a phase shift circuit 11 that can shift only the phase by a desired amount while maintaining the impedance matching of the characteristic impedance has a newly added structure.

In this receiver 10 as well, the first antenna 2 is composed of a whip antenna attached to the main body of a wireless device on which the receiver 10 is mounted so as to be able to be pulled out and stored, and The antenna 3 includes a built-in antenna housed in the main body. This first
Are connected to a phase shift circuit 11 via a matching circuit 6 for performing impedance matching. The phase shift circuit 11 is a circuit for delaying the phase of an input received signal by a desired amount. After delaying the phase of the received signal, the phase shift circuit 11 outputs the received signal to the input terminal a of the selection switch 4. The amount of phase delay of the phase shift circuit 11 is set to a value that minimizes the degree of spatial coupling between the first and second antennas 2 and 3 based on experiments and the like. In particular,
The phase delay amount is such that the phase difference between the signal radiated from the first antenna 2 by reflection and the signal to be received by the second antenna 3 does not become 180 degrees.

On the other hand, the second antenna 4 is directly connected to the input terminal b of the selection switch 4 via a matching circuit 7 for performing impedance matching, as in the prior art. The selection switch 4 connects one of the input terminals a and b to the output terminal c based on the switching control signal S2 from the receiving circuit 5 to receive the signals received by the first and second antennas 2 and 3. The received signal having the higher signal level among the signals is output to the receiving circuit 5 as the received signal S1.

The receiving circuit 5 outputs a switching control signal S1 to the selection switch 4 as appropriate to cause the selection switch 4 to perform a selection operation, and determines a signal level of the reception signal S1 obtained as a result, thereby always receiving a signal. The selection switch 4 selects the higher-level antenna. Thus, the receiving circuit 5 performs a demodulating process on the received signal S1 obtained by such a selecting operation, thereby performing a receiving operation in which the influence of fading is avoided, and receiving data transmitted from the transmitting side. Can be accurately restored.

Here, the configuration of the phase shift circuit 11 is shown in FIG.
As shown in FIG. 2, the phase shift circuit 11 includes capacitors C1 and C2 connected in series between input and output terminals, and a coil L1 connected between the connection midpoint between the capacitors C1 and C2 and ground. And a symmetrical T-type circuit composed of capacitive and inductive reactance elements. Such a phase shift circuit 11 includes capacitors C1, C
2 and the value of the coil L1, the phase delay amount is determined, and the phase of the input received signal is shifted by the phase delay amount.

Since the phase shift circuit 11 has a symmetrical structure, the phase shift is not performed only on the received signal supplied from the first antenna 2 but the input terminal a of the selection switch 4 is connected to the input terminal a of the selection switch 4. When an open end is established, a phase shift is also performed on a received signal reflected from the open end. Therefore, since the signal radiated from the first antenna 2 passes through the phase shift circuit 11 twice, the phase delay amount of the phase shift circuit 11 is set to half of the target phase delay amount.

In the above configuration, in the case of the receiver 10, since the first and second antennas 2 and 3 are arranged close to each other in a distance, the first and second antennas 2 and 3 are connected to each other. Even if they are spatially coupled, it is possible to prevent the signal level of the received signal from being deteriorated by the phase shift circuit 11 beforehand. More specifically, as shown in FIG. 1, when the second antenna 3 is selected by the selection switch 4, the input end a of the selection switch 4 becomes an open end. The signal received at 2 is reflected at the input end a. The reflected reception signal returns to the first antenna 2 and is radiated from the first antenna 2. The signal radiated from the first antenna 2 goes around the second antenna 3 due to the spatial coupling of the first and second antennas 2 and 3.

In the case of a configuration in which no countermeasures are taken as in the prior art, the phase difference between the signal radiated from the first antenna 2 and the signal that should be received by the second antenna 3 is If the angle is shifted by exactly 180 degrees, signal cancellation occurs and the signal level of the signal to be received by the second antenna 3 is degraded. As a result, good diversity reception cannot be performed and the received data can be accurately restored. When it disappeared, inconvenience had occurred.

On the other hand, when the phase shift circuit 11 is provided after the matching circuit 6 of the first antenna 2 as in the receiver 10, the reception by the first antenna 2 is performed by the phase shift circuit 11. A phase delay occurs in the received signal. Therefore, if the amount of phase delay of the phase shift circuit 11 is set to a desired value in advance by experiments or the like, the signal radiated from the first antenna 2 and the signal radiated by the second antenna 3 should be originally received. It is possible to prevent the phase difference from the signal from becoming exactly 180 degrees, thereby avoiding the signal cancellation beforehand, perform good diversity reception without signal deterioration, and improve communication quality.

In this case, the phase shift circuit 11 is provided on the side of the first antenna 2 composed of a whip antenna, thereby preventing signal cancellation on the side of the built-in antenna having a relatively low signal level of the received signal. Therefore, it is possible to effectively prevent the signal level from lowering and perform good diversity reception.

According to the above configuration, the phase shift circuit 11 for delaying the phase of the signal received by the first antenna 2 by a desired amount is provided at the subsequent stage of the matching circuit 6 of the first antenna 2. As a result, it is possible to avoid a decrease in the signal level of the received signal due to the cancellation of the signal in the second antenna 3 beforehand, and perform good diversity reception. Further, by mounting the antenna system having such a configuration on a small-sized portable wireless device, a wireless device capable of performing excellent diversity reception can be realized.

(2) Second Embodiment In FIG. 3, in which parts corresponding to those in FIG. 1 are assigned the same reference numerals, reference numeral 20 denotes a receiver as a whole according to the second embodiment, The major difference from the second embodiment is that a phase shift circuit 21 is newly provided in the subsequent stage of the matching circuit 7 of the second antenna 3.

The phase shift circuit 21 has basically the same configuration as that of the phase shift circuit 11, and is configured to delay the phase of an input received signal by a desired amount. The phase delay amount of the phase shift circuit 21 is set to a value that minimizes the degree of spatial coupling between the first and second antennas 2 and 3 based on experiments and the like. Specifically, the phase difference between the signal radiated from the second antenna 3 by reflection and the signal to be received by the first antenna 2 is 18
This is the amount of phase delay that does not reach 0 degrees.

In the above configuration, in the case of this receiver 20, when the first antenna 2 is selected by the selection switch 4, the received signal received by the second antenna 3 is transmitted to the selection switch 4. Since the input end b is an open end, it is reflected and radiated from the second antenna 3. For the same reason as in the first embodiment, the phase of the received signal is changed by the phase shift circuit 21. Because it is delayed by the desired amount,
It is possible to prevent signal cancellation of a received signal that should be originally received by the first antenna 2. Therefore, also in this case, it is possible to prevent a decrease in the signal level of the received signal, and perform good diversity reception.

Thus, according to the above configuration, the second antenna 3 is also provided after the matching circuit 7 of the second antenna 3.
By providing the phase shift circuit 21 for delaying the phase of the received signal received by the desired amount by a desired amount, it is possible to prevent a decrease in the signal level of the received signal due to cancellation of the signals in the first and second antennas 2 and 3 beforehand. Thus, good diversity reception can be performed. Further, by mounting the antenna system having such a configuration on a small-sized portable wireless device, a wireless device capable of performing excellent diversity reception can be realized.

(3) Third Embodiment In FIG. 4, in which parts corresponding to those in FIG. 1 are assigned the same reference numerals, reference numeral 30 denotes a receiver as a whole according to the third embodiment, The difference from the first embodiment is that the configuration of the phase shift circuit 31 is different from the phase shift circuit 11 of the first embodiment.

As shown in FIG. 4, the phase shift circuit 31 according to this embodiment includes first and second phase shift circuits 31A and 31B having different phase delay amounts. The circuits 31A and 31B can be switched according to the operation mode of the receiver. The internal configurations of the first and second phase shift circuits 31A and 31B are almost the same as the phase shift circuit 11 described in the first embodiment.

The reason for switching between the phase shift circuits 31A and 31B is that the degree of spatial coupling between the first and second antennas 2 and 3 depends on the use state of the portable wireless device on which the receiver 30 is mounted. Because it changes. For example, when the portable wireless device is in a standby state, the portable wireless device is often placed in a bag or the like, and is relatively insensitive to the human body. On the other hand, when the portable wireless device is in a call state, the portable wireless device is located at the head of the human body for a call, so that the portable wireless device is easily affected by the human body. When a human body exists near the antenna, the degree of spatial coupling between the first and second antennas 2 and 3 greatly changes due to various factors such as reflection.
As described above, the degree of spatial coupling between the first and second antennas 2 and 3 greatly changes when the portable wireless device is in the standby state and in the talking state. Therefore, the amount of signal delay required to prevent signal cancellation caused by the spatial coupling also changes.

Therefore, in the third embodiment, a first phase shift circuit 31A having a phase delay amount capable of optimally preventing signal cancellation occurring during standby and a phase capable of optimally preventing signal cancellation occurring during talking. A second phase shift circuit 31B having a delay amount is provided, and these are switched according to a use state.

As shown in FIG. 4, a key signal S3 from an operation key 32 such as a call switch or a call end key is taken into a control circuit 33 for controlling the entire operation of the portable radio device on which the receiver 30 is mounted. It is. When the control circuit 33 detects that the talk key has been pressed based on the key signal S3 from the operation key 32, the receiving circuit 5 and the transmitting circuit (not shown)
To the talk state, and the second phase shift circuit 31B
Is output. When the control circuit 33 detects that the call end key has been pressed based on the key signal S3, the control circuit 33 causes the receiving circuit 5 and the transmitting circuit to transition to the standby state and to select the first phase shift circuit 31A. The control signal S4 is output.

The control signal S4 from the control circuit 33 is supplied to the first and second selection switches 31C and 31C constituting the phase shift circuit 31.
31D. First and second selection switches 31
C and 31D switch the connection state based on the content of the control signal S4, so that the first state is set in the standby state.
Is selected, and the second phase shift circuit 31B is selected during the call state. Thus, the first and second phase shift circuits 31 according to the standby state and the call state as described above.
By switching between A and 31B, an optimal phase shift circuit can be set according to the operation mode.

In the above configuration, the receiver 30 of this embodiment has two phase shift circuits 31 having different phase delay amounts.
A and 31B are provided, and are switched according to the operation mode. In this case, the first phase shift circuit 31
A has an optimal amount of phase delay to prevent signal cancellation caused by spatial coupling of the first and second antennas 2 and 3 during standby, and the second phase shift circuit 31B operates during a call. It has an optimal amount of phase delay to prevent signal cancellation caused by spatial coupling of the first and second antennas 2,3. Therefore, if the first phase shift circuit 31A is selected during standby and the second phase shift circuit 31B is selected during a call, signal cancellation caused by the spatial coupling of the first and second antennas 2, 3 is eliminated. This can be reliably prevented, and diversity reception can be performed even better.

According to the above configuration, the two phase shift circuits 31A and 31B having different phase delay amounts are provided, and the two phase shift circuits 31A and 31B are switched according to the operation mode. And second antennas 2, 3
Can be reliably prevented from occurring due to the spatial combination of the signals, and thus the diversity reception can be more effectively performed. Further, by mounting the antenna system having such a configuration on a small-sized portable wireless device, a wireless device capable of performing excellent diversity reception can be realized.

(4) Other Embodiments In the above embodiment, as shown in FIG.
Capacitors C1, C2 connected in series between input and output terminals
And the case where the phase shift circuit 11 is constituted by the coil L1 connected between the connection midpoint of the capacitors C1 and C2 and the ground, but the present invention is not limited to this, and the present invention is not limited to this. Even when two coils are connected in series and a capacitor is connected between the connection midpoint of the coils and the ground, the same effect as in the above case can be obtained. it can. In short, if the phase circuit is constituted by a symmetric T-type circuit composed of capacitive and inductive reactance elements, the same effect as in the above case can be obtained.

Further, in the above-described embodiment, as shown in FIG. 2, the case where the phase shift circuit 11 is constituted by capacitive and inductive reactance elements has been described, but the present invention is not limited to this. As shown in FIG. 5, a phase shift circuit 41 for delaying the phase of a received signal by a desired amount by using the line length of a high-frequency transmission line 41A such as a microstrip line is also provided. The effect of can be obtained. In this case, since the phase of the signal radiated from the antenna 2 is determined by the line length of the transmission line through which the signal passes, a high-frequency transmission line 41A is inserted between the antenna 2 and the selection switch 4, and the high-frequency transmission line is inserted. If the line length of 41A is set to a desired length, a desired amount of phase delay can be obtained. Therefore, in this example, the line length of the high-frequency transmission line 41A is set to a length corresponding to the amount of phase delay necessary to prevent signal cancellation, thereby preventing signal cancellation as in the above-described case. And good diversity reception can be performed.

In the third embodiment described above,
The case has been described where the selection operation of the first and second phase shift circuits 31A and 31B is performed in conjunction with the call key and the call end key. However, the present invention is not limited to this. Separately, a dedicated key for selecting a phase shift circuit is provided, and the first and second phase shift circuits 31 are operated in accordance with the operation of the dedicated key.
A and 31B may be selected.

In the above embodiment, the phase shift circuit 1 is provided after the matching circuit 6 of the first antenna 2 or after the matching circuits 6 and 7 of the first and second antennas 2 and 3.
Although the case where 1 and 21 are provided has been described, the present invention is not limited to this, and a phase shift circuit may be provided at any other position as long as the position can delay the phase of a signal radiated when not selected. You may do it. The point is that it has first and second antennas and selection means for selecting one of the first and second antennas, and the desired first or second antenna is selected by the selection means. In the antenna device made to perform diversity reception by selecting,
If the phase delay means for delaying the phase of the received signal by a desired amount is provided between the first antenna and the selection means and / or between the second antenna and the selection means, the same effect as in the above case can be obtained. Obtainable.

[0041]

As described above, according to the present invention, the phase delay means for delaying the phase of a received signal by a desired amount between the first antenna and the selection means and / or between the second antenna and the selection means. Is provided, signal cancellation of the received signal can be avoided beforehand, and good diversity reception can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a receiver for diversity reception according to a first embodiment.

FIG. 2 is a block diagram showing a configuration of a phase shift circuit.

FIG. 3 is a block diagram showing a configuration of a receiver for diversity reception according to a second embodiment.

FIG. 4 is a block diagram showing a configuration of a receiver for diversity reception according to a third embodiment.

FIG. 5 is a block diagram showing a configuration of a phase shift circuit according to another embodiment.

FIG. 6 is a block diagram showing a configuration of a conventional receiver for diversity reception.

[Explanation of symbols]

1, 10, 20, 30, 40 ... receiver, 2, 3, ... antenna, 4, 31C, 31D ... selection switch, 5 ...
Receiving circuit, 6, 7, matching circuit, 11, 21, 31, 3
1A, 31B, 41 ... Phase shift circuit, 32 ... Operation keys,
33 ... Control circuit, 41A ... High frequency transmission line.

Claims (12)

[Claims] A first and a second antenna; and a selecting means for selecting one of the first and the second antennas. The first or the second antenna is selected by the selecting means. An antenna device configured to perform diversity reception by selecting two antennas, wherein between the first antenna and the selecting means and / or between the second antenna and the selecting means, An antenna device comprising phase delay means for delaying a phase by a desired amount. 2. The antenna device according to claim 1, wherein said phase delay means comprises a symmetrical T-shaped circuit constituted by capacitive and inductive reactance elements. 3. The antenna device according to claim 1, wherein said phase delay means is constituted by a high-frequency transmission line having a line length corresponding to a phase delay amount. 4. The phase delay means comprises first and second phase delay means having different amounts of phase delay, and the first and second phase delay means are provided in accordance with a use state of a portable wireless device on which the antenna device is mounted. 2. The antenna device according to claim 1, wherein a desired phase delay unit is selected from the two phase delay units. 5. The antenna device according to claim 1, wherein said first antenna comprises a whip antenna, and said second antenna comprises a built-in antenna. 6. The antenna device according to claim 5, wherein said phase delay means is provided between said first antenna comprising at least a whip antenna and said selection means. 7. A first and a second antenna, and a selecting means for selecting one of the first and the second antennas, the first or the second antenna being desired by the selecting means. In a portable wireless device having an antenna device adapted to perform diversity reception by selecting the second antenna, the antenna device may be provided between the first antenna and the selection means, and / or the second antenna. A portable wireless device comprising phase delay means for delaying a phase of a received signal by a desired amount between the selection means. 8. The portable wireless device according to claim 7, wherein said phase delay means comprises a symmetric T-type circuit constituted by capacitive and inductive reactance elements. 9. The portable wireless device according to claim 7, wherein said phase delay means is constituted by a high-frequency transmission line having a line length corresponding to a phase delay amount. 10. The phase delay means comprises first and second phase delay means having different amounts of phase delay, and the first and second phase delay means are provided in accordance with a use state of the portable wireless device. 8. The portable wireless device according to claim 7, wherein a desired phase delay unit is selected. 11. The portable wireless device according to claim 7, wherein said first antenna comprises a whip antenna, and said second antenna comprises a built-in antenna. 12. The portable wireless device according to claim 11, wherein said phase delay means is provided between said first antenna comprising at least a whip antenna and said selection means.