JPS5850059B2 - Reception signal control circuit - Google Patents

Description

[Detailed description of the invention] The present invention relates to a received signal control circuit.

Conventionally, a space diversity method has been used in which a plurality of receivers are switched and used in response to fluctuations in the received signal level.

As a typical example of this received signal control circuit, the circuit shown in the block diagram of FIG. 1 or 2 is used.

In FIG. 1, the received signals of AI and A2 applied to input terminals 114 and 115 pass through branch amplifiers 101 and 102, and after one of them is selected by a switching circuit 103, they are output from an output terminal 116. Sent out.

On the other hand, the signals branched by the branch amplifiers 101 and 102 are compared by the control signal generation circuit 104, and then sent to the switching circuit 10.
Sends a control signal to 3.

The configuration of control signal generation circuit 104 is as shown in FIG.

105 and 106 are buffer amplifiers, 107 is a switch, 1
08 is an amplifier, 109 is an AGC circuit, 110 and 111 are synchronous detection circuits, 112 is a logic circuit, and 113 is a switching oscillator.

In response to the switching signal from the switching oscillator 113, the switching circuit 107 alternately switches and outputs each received signal from the amplifiers 105 and 106.

The output from this switching circuit 107 is supplied to synchronous detectors 110 and 111 after passing through an amplifier 108 with an AGC circuit.

Since the synchronous detectors 110 and 111 are configured to operate in conjunction with the switching circuit 107 by the switching signal from the oscillator 11'3, received signals corresponding to AI and A2 are obtained at their outputs, respectively.

The logic circuit 112 compares the levels of the detected outputs thus obtained and controls the switching circuit 103 to select the received signal with the higher level.

In other words, the circuit shown in FIG. 1 always selects and outputs the received signal having a higher input level in response to fluctuations in the two received signals.

Although the present control signal generation circuit 104 is excellent in terms of control refinement, it is expensive due to its complicated configuration.

Furthermore, an example of a conventional circuit shown in FIG. 2 will be explained.

121 and 122 are amplifiers, the gains of which are controlled by AGC circuits 123 and 124.

The output levels 125 and 126 of the AGC circuits 123 and 124 change according to the signal levels of the input terminals 114 and 115, and these two signals are compared in a comparison circuit 127 to control the switch 103.

This method has a simpler configuration than the method shown in FIG.
Since the linearity of 126 is not very good, there is a drawback that control errors are likely to occur.

SUMMARY OF THE INVENTION An object of the present invention is to provide a received signal control circuit that has a very simple configuration and can perform control with very little error, which has been devised to eliminate these conventional drawbacks.

Next, the present invention will be explained by examples.

FIG. 3 shows a received signal level detection circuit according to an embodiment of the present invention, and FIG. 4 shows a circuit diagram of an embodiment of switch control when the circuit of FIG. 3 is used.

The received signal applied to the input terminal 14 is amplified by a saturation type amplifier 11 composed of n stages having a limiter function, and then becomes a constant level and is sent out from the terminal 15.

When the signal level applied to the terminal 14 increases from a low level state, the amplifiers 11 are sequentially directed from amplifier n at the final stage to previous stages (n-1), (n-2), etc. ...2,
It becomes saturated at 1.

These levels are detected by a detector 12 (
1, 2, .

Figure 5 shows the terminal 14 in Figure 3 in the case of a five-stage detection circuit.
Person level vs. each detector 12 and adder 13 output terminal 1
6, a signal with very good linearity can be obtained from terminal 16.

Figure 4 is an example of controlling a switch using the circuit shown in Figure 3, with AI and A2 applied to terminals 25 and 26.
The received signals are respectively amplified by the level detection circuits 21 and 22 in FIG. 3, selected by the switch 23, and sent out from the output terminal 27.

Signals with good linearity from detection circuits 21 and 22 28 and 29
are compared in a comparison circuit 24, and if a difference greater than a certain standard occurs between the two signal levels, a signal is sent to a switch to preferentially select the signal with better transmission quality.

The example shown in FIG. 4 is a case of switching using RF or IP signals, but switching using baseband signals can also be performed in a similar manner by using a demodulator after the level detection circuits 21 and 22.

Further, the circuit for the signal 23 may be a composite image instead of a switch.

As explained above, a control circuit with a very simple configuration and little control error is possible, and by using this, a switching device and a combining device with stable operation and low cost can be constructed.

[Brief explanation of the drawing]

1 and 2 are block diagrams of a conventional reception control circuit, FIG. 3 is a block diagram of a level detection circuit according to an embodiment of the present invention, FIG. 4 is a block diagram of an embodiment of the present invention, and FIG. 5 is the characteristic diagram of FIG. In the figure, IL 108, 121.122...
・Amplifier, 12...Detector, 13...
Adder, 14°25.26, 114, 115...
・Reception input terminal, 15.27, 116... Output terminal, 16... Control output terminal, 23, 103,
107...Switcher, 24°127...
Comparison circuit, 28, 29... Addition output terminal, 10
1,102...branch amplifier, 104...
・Control signal generation circuit, 105, 106...Buffer amplifier, 109, 123, 124...AG
C circuit, 110.111... Synchronous detection circuit, 1
12...Logic circuit, 113...Switching oscillator, 125°126...AGC output terminal.

Claims (1)

[Claims] 1 Each of a plurality of receiving systems is provided with an input reception level detection circuit consisting of a detection circuit connected to each stage of a saturation multistage amplifier and an adder circuit that adds the detected outputs, and the detection circuit of these receiving systems. A received signal control circuit comprising a circuit that compares the outputs of the plurality of receiving systems and controls the synthesis or switching of the outputs of the plurality of receiving systems in response to the comparison result.