JPH07112171B2 - Space diversity reception system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a space diversity receiving system used for microwave digital communication.

[0002]

2. Description of the Related Art In the space diversity receiving system, 2
By combining the phases of the received signals received by the original antenna after combining them, the interference components included in the received signals are canceled each other, and the influence of the deterioration of the S / N ratio due to fading or the like can be suppressed. .

FIG. 3 shows the configuration of a conventionally known space diversity receiving system. In this figure, the received signals received by the two antennas A1 and A2 are respectively amplified by the main system and sub system variable gain amplifiers 3 and 4, and then the output levels of the amplifiers 3 and 4 are detected by the level detector. It is detected at 6 and 7. Detection signals of these output level detectors 6 and 7 are sent to an automatic gain control circuit 9 (hereinafter referred to as an AGC control circuit), and a common automatic gain control voltage (hereinafter referred to as AGC voltage) output from the AGC control circuit 9 is output. The gain of the two amplifiers 3 and 4 is controlled by the above.

In the space diversity receiving system using the in-phase combining means, if the amplifiers 3 and 4 are individually gain-controlled, the receiving input level of one of them is lowered and the signal-to-noise ratio is deteriorated. In this case, if the signal level is raised, the signal-to-noise ratio of the in-phase combined output will be affected. Therefore, in order to suppress this effect, the conventional method uses the one with the larger absolute value of the AGC voltage, The AGC voltage of the higher input level is commonly used by the amplifier 3,
In addition to 4, the gains of the two amplifiers 3 and 4 were controlled to be kept equal.

Further, in the space diversity receiving system described in Japanese Patent Application Laid-Open No. 61-131625, there is a problem in FIG.
As shown in, the detection level value in the amplitude detector 22 for detecting the output level after the in-phase combination is maximized,
Transporter 20 connected to the output of one variable gain amplifier 4
The controller 23 controls the gains of the amplifiers 3 and 4 based on the outputs of the level detectors 6 and 7 so that the level of the combined output becomes large within a range where the two variable gain amplifiers 3 and 4 are not distorted.
It is configured to be controlled by.

[0006]

However, in the conventional space diversity receiving system shown in FIG. 3, since the gains of the amplifiers 3 and 4 are controlled by the common AGC voltage, the AGC of the two amplifiers 3 and 4 is controlled. If there is a difference in the voltage-gain characteristics, the gains of the two amplifiers 3 and 4 are not equal. Further, when there is a difference in the characteristics of the amplifiers 3 and 4, there arises a problem that the AGC voltage must be finely adjusted in accordance with the characteristics of the amplifiers 3 and 4 in order to equalize the gains.

In the space diversity receiving system shown in FIG. 4, the S / N ratio of the output of the combiner 21 is better than that of the system without the variable gain amplifier. Since the gains of the two are not equal, the S / N ratio of the output of the combiner is
The S / N ratio up to the input of 1 is dominated by the worse one.
For example, when the S / N ratio of the received signal in the main system is lower than that in the sub system, and the gain of the variable gain amplifier 3 on the main system side is large,
The S / N ratio of the combiner output may be worse than the S / N ratio of the reception signal of the sub system.

The present invention has been proposed in order to solve the problems of the prior art as described above, and it is possible to avoid the problems that occur when two AGC voltages are shared by two variable gain amplifiers, and at the same phase. S / of output signal after synthesis
An object of the present invention is to provide a space diversity receiving system capable of increasing the N ratio.

[0009]

To achieve this object, the present invention provides a main system and a sub system for amplifying a received signal received by a main antenna and a received signal received by a sub antenna, respectively. In a space diversity reception system having one amplifier and an in-phase combiner for combining the output signals of these two amplifiers in the same phase, first and second detecting the levels of the input signals to the main system amplifier and the auxiliary system amplifier, respectively. A second input level detector, first and second output level detectors for detecting the levels of the output signals from the main system and sub system amplifiers, respectively, a first input level detector and a second < br /> output level detector of the detection level value of the comparison result, and based on a second input level detector and a comparison result of the detected level value of the first output level detector, of the main system and the secondary system < br /> amplifier As the gain is always equal is configured to include a control unit for controlling the gain of the amplifiers, respectively.

Preferably, the control section includes first and second reference voltage generators for generating reference voltages corresponding to the detection outputs of the first and second input level detectors, respectively. a first comparator for comparing the reference voltage and the detection level value of the output level detector of the second <br/> from the reference voltage generator, the reference voltage and the first from the second reference voltage generator < The second comparator for comparing the detection level value of the output level detector of <br/> with the two of the main system and the sub system so that the comparison result of the first and second comparators becomes zero. A first automatic gain control circuit and a second automatic gain control circuit which respectively control the gain of the amplifier.

[0011]

According to the above-mentioned structure, the input / output levels of the main system amplifier and the auxiliary system amplifier are detected, the detected output of the input / output level is compared for each system, and the two amplifiers are detected based on the comparison result. Since the gains can be controlled individually, the gains of the two amplifiers can always be made equal.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a space diversity receiving system according to the present invention. In this figure, the signal received by the main antenna A1 is amplified by the variable gain amplifier 3 to a level at which non-linear distortion does not occur, and is supplied to the in-phase combiner 5. The signal received by the sub-antenna A2 is similarly amplified by the variable gain amplifier 4 and supplied to the in-phase combiner 5. In the in-phase combiner 5, the output signals of the two amplifiers 3 and 4 are combined so that they have the same phase, and are taken out to the output terminal OUT.

The input signal levels to the main system and sub system amplifiers 3 and 4 are the first and second input level detectors 1 and 2.
Respectively detected by the first and second reference voltage generators 11 and 11 in the control unit 8 shown in FIG.
12 are supplied respectively. These reference voltage generators 1
In reference numerals 1 and 12, reference voltages V1 and V2 corresponding to the respective input levels detected by the detectors 1 and 2 are generated, and these reference voltages V1 and V2 are applied to the first and second comparators 13 and 1, respectively.
4 respectively. In this way, the reference voltages V1 and V corresponding to the input levels are generated by the reference voltage generators 11 and 12.
By generating 2, the gain setting of the amplifiers 3 and 4 becomes possible. The output signals from the amplifiers 3 and 4 are
Detected by the first and second output level detectors 6, 7.
The detection signals S3 and S4 are output to the comparators 13 and 14 in the control unit 8.
Is supplied to each.

In the comparator 13, the reference voltage V1 corresponding to the input signal level of the main system is compared with the output signal level S3 of the sub system , and the comparison output is supplied to the first AGC control circuit 15. On the other hand, in the comparator 14, the reference voltage V2 corresponding to the input signal level of the sub system is compared with the output signal level S4 of the main system , and the comparison output is supplied to the second AGC control circuit 16.

The AGC control circuit 15 produces an AGC control voltage S5 for controlling the gain of the main system amplifier 3 so that the comparison output from the comparator 13 becomes zero, and the AGC control circuit 16 produces a comparator. AGC for controlling the gain of the auxiliary amplifier 4 so that the comparison output from 14 becomes zero.
A control voltage S6 is created.

When there is a difference between the signal levels received by the amplifiers 3, bells and the sub-antenna A2 due to the AGC control voltages S5, S6 output from the control unit 8, the level difference is compared with the comparator 13 and And / or 14
The lower of the amplifier by the level difference amount reception level 3 or 4
It is possible to perform the in-phase synthesis in a state in which the output level of is reduced and the gains of the main system and sub system amplifiers 3 and 4 are always equalized. As a result, the S / N ratio of the in-phase combined output can be maintained high. By controlling the gain of No. 4, the signal level received by the main antenna A1 is

[0017]

As described above, according to the present invention, the input level and the output level of the amplifiers of the main system and the sub system are respectively detected, and the comparison result of the detection output of the input and output levels of the main system and the sub system is obtained. The gains of the amplifiers are controlled based on the gains of the amplifiers, even if the received signal levels of the main antenna and the sub-antenna are different or the AGC voltage-gain characteristics of the amplifiers are different. There is an effect that the in-phase synthesis can be performed in a state where the two are equal. As a result, the AGC required when the AGC voltage is common
There is an advantage that fine adjustment of the voltage becomes unnecessary and the S / N ratio of the in-phase combined output can be increased even when the level of the input signal of one system is low.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a space diversity receiving system according to the present invention.

FIG. 2 is a block diagram showing an internal configuration of a control unit in FIG.

FIG. 3 is a block diagram showing a conventional space diversity receiving system.

FIG. 4 is a diagram showing another conventional space diversity receiving system.

[Explanation of symbols]

 A1 Main antenna A2 Sub-antenna 1, Input level detector 3,4 Amplifier 5 In-phase combiner 6,7 Output level detector 8 Control section 11,12 Reference voltage generator 13,14 Comparator 15,16 AGC control circuit

Claims (2)

[Claims] 1. A main system and a sub system for amplifying a received signal received by a main antenna and a received signal received by a sub antenna, respectively.
In a space diversity reception system having two amplifiers of 1) and an in-phase combiner for combining the output signals of these two amplifiers in phase, the level of the input signal to each of the main system and sub system amplifiers is detected. First and second input level detectors, first and second output level detectors that detect the levels of the output signals from the main system and sub system amplifiers, respectively, and a first input level detector and a second input level detector . Based on the comparison result of the detection level values of the second output level detector and the comparison result of the detection level values of the second input level detector and the first output level detector, the gains of the main system and sub system amplifiers A space diversity receiving system characterized by having a control unit for controlling the gains of these amplifiers so that the values are always equal to each other. 2. The first and second reference voltage generators for generating the reference voltages according to the detection outputs of the first and second input level detectors, respectively, and the first reference voltage. A first comparator that compares the reference voltage from the generator with the detection level value of the second output level detector, and a reference voltage from the second reference voltage generator and the detection of the first output level detector A second comparator for comparing the level value with the first and second gains for controlling the gains of the two amplifiers of the main system and the sub system, respectively, so that the comparison result of the first and second comparators becomes zero. The space diversity receiving system according to claim 1, wherein the space diversity receiving system comprises a second automatic gain control circuit.