JPH02143720A - Space diversity reception system - Google Patents

Abstract

PURPOSE:To improve S/N by using the output of an automatic gain controller (AGC) to control a variable attenuator (V-ATT) provided to an output terminal of a receiver. CONSTITUTION:An antenna (ANT) 1 and a receiver (RX) 1 are connected and the output terminal of the receiver is provided with the 1st system connecting the AGC 1 and the V-ATT 1 and with the 2nd system provided with the ANT 2, the RX2, the AGC2 and the V-ATT2 similarly. Each system is operated similarly. For example, in the system, the V-ATT 1 is controlled provided to the output terminal of the RX 1 by the output of the AGC 1. Thus, the synthesized output S/N is operated to be maximized.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a space diversity reception system for a receiver equipped with an AGC circuit.

(Prior Art) FIG. 2 shows a space diversity reception system that has been conventionally used to compensate for the effects of fading phenomena in which radio wave propagation conditions change due to changes in atmospheric density, reflections from the ground surface, and the like.

As shown in the figure, the antennas ANTI and ANT2 have N'& for a period of two or more in order to compensate for the influence of fading phenomenon on radio waves, and the signals input multiple times to the respective antennas are sent to the receivers RXI and RX2. It demodulates and amplifies the output signal of the AGC so that it has a certain value, and furthermore, in order to maximize the level of the low frequency signal, the mutual receiver output signals are synthesized and output in the same phase. be.

However, in the above method, when the input signal level of one receiver is low as shown in Figure 3 (S) and the input signal level of the other receiver is high as shown in Figure 3 (H), the respective receiver output signals are is amplified to a certain value by an independent AGC to obtain a signal with a low S/N and a signal with a high S/H as shown in Figures 3 and 3. Furthermore, by making the phase of each signal the same and inputting them to the synthesizer ADD, only a very low signal of 87N as shown in Figure 3 (sword) is obtained as an output. In addition, if a switch is installed at each output end of the receiver, when the S/N of one receiver's output signal is poor, if switch Z is operated so as not to combine the output signals, the output signal will not be combined. There was a drawback that the S/N in the input signal could not be improved more than the S/N in the input signal.

(Objective of the Invention) As described above, an object of the present invention is to provide a reception signal system that operates to maximize the combined output S/N in the conventional space diversity reception system.

(Summary of the invention) When combining and outputting signals received by a space diversity reception method using a plurality of receivers equipped with independent AGC in order to monitor received electric field strength, the above-mentioned A
A circuit is configured so that the variable attenuator (V, ATT) provided at the output end of each receiver is controlled by the GC output.

(Example) The present invention will be described in detail below based on the illustrated embodiments.

FIG. 1 is a block diagram showing one embodiment of the present invention, and the same symbols as in the block diagram of the conventional circuit shown in FIG. 2 have the same meanings.

In the figure, ANTI is an antenna, the antenna is connected to a receiver RXI, and the output terminal of the receiver is connected to an AGC1
and the first system connected with variable attenuator V-ATT1'4, and similarly ANT2. RX2゜AGC2, V-A'l"
l' 2 , the output end of the variable attenuator V-ATT1 in the first system is connected to the output end of the combiner ADD, and the second system The output terminal of the variable attenuator V-ATT2 is connected to the infinite phase shifter P8.

The output terminal of the PS is connected to the other input terminal of the ADD, and the output terminal of the ADD is connected to a load and a rectifier DET. The output terminal of the DET is connected to the phase control circuit C0NT, and the output terminal of the DET is connected to the phase control circuit C0NT.
The output end of ON'l' is connected to the PH.

In the circuit configured as described above, each system operates in the same way, so to simplify the explanation, the operation of only one system will be explained.

As shown in the prior art, the antenna ANTI is shown in Fig. 4 (a).
As shown in the figure, signals and noise in a band with a center frequency fc are input and demodulated and amplified by a receiver.

The amplification degree of the receiver is determined by inputting the AGC output signal obtained by detecting the receiver output by AGC to the receiver, and the AGC characteristics are shown in FIG.

As shown in the figure, when the output level of one receiver is low, the output of the AGC is increased to increase the amplification degree of the receiver.

Furthermore, a variable attenuator V- is connected to the output terminal of the receiver RXI.
ATTI operates on the output of AG (2) in the opposing second system. When the AGC output is high, the attenuation of V-A'l"l' is set to be low (and when the AGC output is low, the attenuation of V-AT T is set to be high. In other words, the signal level is set to one antenna. When a high signal and a signal with a low signal level are input to the other antenna, the AGC output in the system on the high input signal side will be low, and the attenuation of the variable attenuator V-A'l"l' in the other system will be reduced accordingly. At this time, the signal level input to other systems is low as shown in FIG. 4 (CI), and the S/N is low, so the signal with the low S/N? The attenuation is performed as shown in Fig. 4 (f).

Furthermore, in order to make the phases of the outputs of both systems the same, an infinite phase shifter PS is installed in one system, and the in-phase output signals are sent to a combiner ADD.
The signals are added as shown in FIG. 4 (g) and outputted.

To control the infinite phase shifter Pa, the output of the synthesizer ADD is rectified by the rectifier DET, and the DET output is connected to the control circuit CO.
N'l'K is input, and the infinite phase shifter is controlled by the C0NT output.

It is clear that the S/N of the output signal of the circuit operated as described above is significantly improved compared to the output signal of the conventional circuit, and furthermore, when the S/N of one input signal is extremely low, Since the signals input to each system can also be combined, the S/N ratio can be improved.

(Effects of the Invention) Since the present invention is configured and operates as described above, the noise level of the signals input to each antenna in the space diversity reception system is suppressed and combined, so that the S/ This has the effect of improving N.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a block diagram of a conventional circuit, FIG. 3 is a diagram showing signal states at each block point in FIG. 2, and FIG. 4 is a block diagram of an embodiment of the present invention. A diagram showing the signal status at each block point in Figure 1, Figure 5 is for AG
FIG. 6 is a diagram showing the operating characteristics of V-ATT. ANTI, ANT2...Antenna. AGCI, AGC2...0 gain control device. V-ATTI, V-ATTz......Variable attenuator. RXI, RX2---Receiver, P
S・・・・・・Infinite phase shifter, C0NT・
・・・・・・・・・Phase control circuit, DB'l'・
...... Rectifier ADD ...... Combiner. -RS0LJT 5th figure → V-ATv AttenueLtAory Vo/uyne ”it figure dormitory 6th figure

Claims (1)

[Claims] When combining and outputting signals received by the space diversity reception method using multiple receivers equipped with independent automatic gain control devices (hereinafter referred to as AGC), the output of each receiver is determined by the AGC output. A space diversity reception system characterized by controlling a variable attenuator V-ATT provided at the end.