JP2002335197A - Diversity radio - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a diversity radio having no loss at the antenna joint. SOLUTION: The diversity radio comprises a plurality of antennas 21 and 22, an antenna switch 23 for selecting either the plurality of antennas, a transmission circuit 25 for up-converting a modulated signal into a signal of radio frequency, a reception circuit 26 for down-converting the frequency of a received signal, a switch 24 for switching between the transmission circuit and the reception circuit, a section 27 for modulating/demodulating data, and a section 28 for processing data where impedance is matched with that of the transmission circuit, for at least either of the plurality of antennas and is matched with that of the receiving circuit for at least one antenna, except at least one of the plurality of antennas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diversity radio used for radio communication and the like.

[0002]

2. Description of the Related Art Antenna diversity used for wireless communication and the like is an effective means for removing the influence of fading, and aims at improving the quality of wireless communication by using two or three or more antennas having low correlation. is there. A typical example of this is space diversity.

[0003] Spatial diversity is based on the fact that the manner in which fading changes at points far from each other near a receiving point is independent of each other. Usually, two or more antennas are spatially separated from each other,
At the time of reception, the signals are separately received, and then the signals are combined or switched for use. During transmission, the reverse process is performed.

FIG. 3 is a block diagram showing a conventional diversity radio, showing an antenna selection space diversity radio.

In FIG. 3, reference numerals 11 and 12 denote antennas, 1
3 is an antenna switch for selecting an antenna to be used, 1
Reference numeral 4 denotes a transmission / reception switch for selecting a transmission circuit 15 or a reception circuit 16 described later. Reference numeral 15 denotes a transmission circuit for up-converting modulated data to a radio frequency. Reference numeral 16 denotes a reception circuit for down-converting a received radio signal. And a data processing unit 18 for processing transmission / reception data.

In FIG. 3, the impedance when viewing the antenna 11 side from point A is Z1a, and the circuit side (in this case, the transmitting circuit 15 side) is viewed from point A when the antenna switch 13 selects the antenna 11. The impedance at the time of transmission is Z1t, the impedance at the time of reception when viewing the circuit side (in this case, the reception circuit 16 side) from point A when the antenna switch 13 selects the antenna 11 is Z1r, and the impedance at the antenna 12 side from point B. Z2a is the impedance when the antenna switch 13 selects the antenna 12, and the impedance when the transmission is viewed from the point B when the antenna switch 13 selects the antenna 12 is Z2a
t, the impedance at the time of reception when the circuit side is viewed from the point B when the antenna switch 13 selects the antenna 12 is Z2r. Now, assuming that impedance matching is performed at 50Ω, an attempt is made to adjust all the impedances to 50Ω. However, it is difficult to make all impedances completely 50 Ω, and in fact, they often shift slightly. For example, when the impedance Z1t at the time of transmission and the impedance Z1r at the time of reception are not equal (Z1t ≠ Z1t) when the circuit side is viewed from the point A, if the impedance Z1a of the antenna 11 and the impedance Z1t of the circuit of the transmission system are matched. If it is taken (that is, Z1a = Z1t *; * represents complex conjugate), matching with the impedance Z1r of the receiving circuit 16 cannot be achieved (Z1a ≠ Z1r *), and there is no problem at the time of transmission. Sometimes a loss due to impedance mismatch occurs. Conversely, if the impedance Z1a of the antenna 11 is matched with the impedance Z1r of the receiving circuit 16 (Z1a = Z1r *), the impedance Z1t of the transmitting circuit 15 cannot be matched (Z1a ≠ Z1t *). Loss due to impedance mismatch will occur during transmission. As described above, it is difficult to completely achieve impedance matching between transmission and reception, and at present, transmission and reception are designed to allow a loss to a certain level, and diversity is performed using a plurality of similarly designed antennas.

[0007]

As described above, the conventional diversity radio apparatus has a problem that it is difficult to perfectly match impedance for transmission and reception. However, the loss at the antenna coupling section has a direct and significant effect on the communication quality and should be minimized.

[0008] In this diversity radio, it is required that there be no loss in the antenna coupling section.

An object of the present invention is to provide a diversity radio having no loss at an antenna coupling section in order to satisfy this requirement.

[0010]

In order to solve the above-mentioned problems, a diversity radio according to the present invention comprises a plurality of antennas, an antenna switch for selecting one of the plurality of antennas, and a modulated signal. A transmission circuit for up-converting the received signal to a radio frequency, a reception circuit for down-converting the received signal, a transmission / reception switch for switching between the transmission circuit and the reception circuit, a modulation / demodulation unit for modulating / demodulating data, and a data processing for processing data And at least one of the plurality of antennas has impedance matching with the transmitting circuit, and at least one of the plurality of antennas other than at least one antenna has impedance matching with the receiving circuit. It has a configuration.

Thus, a diversity radio having no loss at the antenna coupling section can be obtained.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A diversity radio according to a first aspect of the present invention includes a plurality of antennas, an antenna switch for selecting one of the plurality of antennas, A transmission circuit that up-converts the received signal, a reception circuit that down-converts the received signal, a transmission / reception switch that switches between the transmission circuit and the reception circuit, a modulation / demodulation unit that modulates / demodulates data, and a data processing unit that processes data. Provided, at least one of the plurality of antennas is impedance-matched with the transmission circuit, and at least one antenna other than the at least one of the plurality of antennas is impedance-matched with the reception circuit. Things.

With this configuration, it is possible to connect different antennas at the time of transmission and at the time of reception to achieve impedance matching, so that there is an effect that loss at the antenna coupling portion can be eliminated.

According to a second aspect of the present invention, there is provided the diversity radio device according to the first aspect,
The antenna switch preferentially selects an antenna that has impedance matching with the transmitting circuit at the time of transmission, and preferentially selects an antenna that has impedance matching with the receiving circuit at the time of receiving.

According to this configuration, since impedance matching can be achieved for both transmission and reception, there is an effect that loss at the antenna coupling portion can be eliminated.

According to a third aspect of the present invention, there is provided the diversity radio device according to the first aspect.
The antenna switch selects an antenna by diversity at the time of reception, and fixedly selects an antenna having impedance matching with the transmission circuit at the time of transmission.

With this configuration, the antenna is fixed at the time of transmission, and the control amount can be reduced.

A diversity radio according to a fourth aspect is the diversity radio according to the first aspect,
The antenna switch switches the antenna at an arbitrary cycle when waiting for reception, and selects the antenna at the time when the desired wave is detected.

According to this configuration, an antenna capable of detecting a desired wave is selected, and an effect of increasing the success rate of reception can be obtained.

According to a fifth aspect of the present invention, in the diversity wireless device of the first or fourth aspect, the antenna switch selects the same antenna at the time of transmission and at the time of reception immediately before the time of the transmission. It was done.

According to this configuration, the antenna having the best reception level or the like is selected, and the effect of fading can be reduced.

FIG. 1 shows an embodiment of the present invention.
This will be described with reference to FIG.

(Embodiment 1) FIG. 1 is a block diagram showing a diversity radio apparatus according to Embodiment 1 of the present invention.

In FIG. 1, reference numeral 21 denotes a first antenna, 2
2 is a second antenna, 23 is an antenna switch for selecting an antenna to be used, 24 is a transmission / reception switch for selecting a transmission circuit 25 or a reception circuit 26 described later, and 25 is a transmission for up-converting modulated data to a radio frequency. Circuit, a receiving circuit for down-converting the received radio signal, 27 a modulation / demodulation unit for performing data modulation / demodulation, and 28
Is a data processing unit for processing transmission / reception data.

The characteristics, operation, and the like of the diversity wireless device configured as described above will be described with reference to FIGS. 2 (a) and 2 (b). 2A is a block diagram showing a case where the first antenna 21 is connected by the antenna switch 23, and FIG. 2B is a block diagram showing a case where the second antenna 22 is connected by the antenna switch 23. is there.

In FIG. 1, the first antenna 2
The impedance when viewing the circuit side (in this case, the transmitting circuit 25 side) from point A when the antenna switch 23 selects the first antenna 21 is Z1t, and the impedance when viewing the first side is Z1a. Switch 23 is the first
When the antenna 21 is selected, the impedance at the time of reception when the circuit side (the receiving circuit 26 side) is viewed from the point A when the antenna 21 is selected is Z1r, the impedance when the second antenna 22 side is viewed from the point B is Z2a, The antenna switch 23 is the second
The impedance at the time of transmission when the circuit side is viewed from the point B when the antenna 22 is selected is Z2t, and the reception when the circuit side is viewed from the point B when the antenna switch 23 is selecting the second antenna 22. The impedance at the time is Z2r. Now, the impedance Z1a of the first antenna 21
And impedance Z1t at the time of transmission when the circuit side is viewed from point A
In addition, the impedance Z2a of the second antenna 22 is matched with the impedance Z2r at the time of reception as viewed from the point B on the circuit side. That is, Z1a = Z1t
*, Z2a = Z2r *. At this time, at the time of transmission, FIG.
As shown in (a), the first antenna 21 is preferentially selected,
At the time of reception, by controlling the antenna switch 23 so as to preferentially select the second antenna 22 as shown in FIG. 2B, it is possible to transmit a signal without loss at the antenna coupling unit in both transmission and reception. The conventional diversity wireless device allows a transmission and reception loss of about 1 dB in both transmission and reception, and the diversity wireless device according to the present embodiment can improve the communication distance by over 10%.

When the communication quality of the selected antenna deteriorates below a certain level, it is assumed that diversity is performed by selecting another antenna. For example, the received electric field strength at the receiving antenna is monitored, and assuming that the signal is being received by the second antenna 22 as shown in FIG. When a lower value is detected, the antenna switch 23 is switched so that the signal is received by the first antenna 21. At this time, the impedance Z1a of the first antenna 21 is out of matching with the impedance Z1r at the time of reception when the circuit side is viewed from the point A,
By setting = 〜Z1t (= 〜 means substantially equal), loss can be minimized. If Z1r = と Z1t cannot be set, a level at which the antenna is switched is set in consideration of the loss due to the impedance mismatch. For example, assuming that the threshold of the received electric field strength when switching from the second antenna 22 to the first antenna 21 is R21 (dBm) and the loss due to the impedance mismatch is L (dB), The threshold value R12 of the reception electric field strength when switching to the second antenna 22 is set to R12 = R21 + L (dB
m). By doing so, accurate diversity can be achieved.

Further, by fixing the antenna at the time of transmission to the first antenna 21 having impedance matching with the transmission circuit 25, control for determining the transmission antenna can be reduced.

Further, the diversity at the time of waiting for reception can be obtained by switching the antenna switch 23 at regular intervals.
When the desired wave is detected, the antenna that has received the desired wave is selected. At this time, if the selected antenna has an impedance matching with the receiving circuit 26, the antenna is received as it is. If the selected antenna is an antenna that is not matched with the receiving circuit 26, reception may be continued with that antenna. However, an antenna that is matched with the receiving circuit 26 has better communication quality. If you like, you may switch to that antenna.

Further, as an example of performing transmission diversity, antenna selection diversity is performed based on the received electric field strength at the time of reception, and the same antenna as at the time of reception is selected at the time of transmission to perform transmission. For example, the radio wave propagation path at the time of transmission is equal to the radio wave propagation path at the time of reception. Since fading is gradual in time as compared with the transmission / reception switching cycle, the above method enables transmission diversity that can reduce the effects of fading.

In this embodiment, the case where two antennas are used is shown. However, the present invention is not limited to this case, and three antennas are used.
It can be applied to more than one case, and has the same effect.

[0032]

As described above, according to the diversity radio device of the first aspect of the present invention, a plurality of antennas, an antenna switch for selecting any one of the plurality of antennas, and a modulated antenna. A transmission circuit that up-converts the received signal to a radio frequency, a reception circuit that down-converts the received signal, a transmission / reception switch that switches between the transmission circuit and the reception circuit, a modulation / demodulation unit that modulates / demodulates data, and processes data. A data processing unit, wherein at least one of the plurality of antennas is impedance-matched with the transmitting circuit, and at least one of the plurality of antennas other than at least one is impedance-matched with the receiving circuit. By connecting separate antennas for transmission and reception, It is possible to take a dance matching, advantageous effect can be eliminated loss of the antenna coupling unit can be obtained.

According to the diversity wireless device of the second aspect, in the diversity wireless device of the first aspect, the antenna switch preferentially selects an antenna having impedance matching with the transmission circuit at the time of transmission. However, by preferentially selecting an antenna that has impedance matching with the receiving circuit at the time of reception, impedance matching can be achieved for both transmission and reception, which has the advantageous effect of eliminating loss at the antenna coupling section. can get.

According to the diversity radio device of the third aspect, in the diversity radio device of the first aspect, the antenna switch selects an antenna by diversity at the time of reception, and performs impedance matching with the transmission circuit at the time of transmission. By fixedly selecting the antenna being taken, the antenna is fixed at the time of transmission, and an advantageous effect that the control amount can be reduced can be obtained.

According to the diversity wireless device of the fourth aspect, in the diversity wireless device of the first aspect, the antenna switch switches the antenna at an arbitrary period when waiting for reception and detects a desired wave. By selecting an antenna in the above, an antenna capable of detecting a desired wave is selected, and an advantageous effect that the success rate of reception can be increased can be obtained.

According to the diversity radio described in claim 5, in the diversity radio described in claim 1 or 4, the antenna switch selects the same antenna at the time of transmission and at the time of reception immediately before the transmission. By doing
The best antenna in the reception level etc. is selected,
The advantageous effect that the influence of fading can be reduced can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a diversity radio device according to a first embodiment of the present invention.

FIG. 2A is a block diagram illustrating a case where a first antenna is connected by an antenna switch. FIG. 2B is a block diagram illustrating a case where a second antenna is connected by an antenna switch.

FIG. 3 is a block diagram showing a conventional diversity radio.

[Explanation of symbols]

 Reference Signs List 21 first antenna 22 second antenna 23 antenna switch 24 transmission / reception switch 25 transmission circuit 26 reception circuit 27 modulation / demodulation unit 28 data processing unit

Claims (5)

[Claims] 1. A plurality of antennas, an antenna switch for selecting one of the plurality of antennas, a transmission circuit for up-converting a modulated signal to a radio frequency, and down-converting a received signal. A reception circuit, a transmission / reception switch for switching between the transmission circuit and the reception circuit, a modulation / demodulation unit for performing data modulation / demodulation, and a data processing unit for processing data, and at least one of the plurality of antennas For impedance matching with the transmission circuit,
A diversity wireless device, wherein impedance matching is performed on at least one antenna other than at least one of the plurality of antennas with the receiving circuit. 2. The antenna switch preferentially selects an antenna having impedance matching with the transmitting circuit during transmission, and preferentially selects an antenna having impedance matching with the receiving circuit during reception. The diversity wireless device according to claim 1, wherein 3. The diversity radio according to claim 1, wherein the antenna switch selects an antenna by diversity at the time of reception, and fixedly selects an antenna having impedance matching with the transmission circuit at the time of transmission. 4. The diversity radio device according to claim 1, wherein the antenna switch switches an antenna at an arbitrary cycle when waiting for reception, and selects an antenna when a desired wave is detected. 5. The diversity radio according to claim 1, wherein the antenna switch selects the same antenna at the time of transmission and at the time of reception immediately before the transmission.