JPS5944837B2 - signal receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a signal receiver that receives push button signals and the like.

When signals are transmitted using the so-called end-to-end method in which data is transmitted from subscriber terminals to a central data receiving device using pushbutton signals, echoes may occur due to the 4-wire loop at the relay stage (see Literature 1EEE
TRAN5ACT10N50NC0MMUN1CAT1
0NTECHN0L0GYV0L, C0M-15｜N0
．． 6DEC67PP812-824).

Therefore, a multi-frequency signal receiver that receives these data requires protection means to prevent it from being affected by echoes. Conventionally, as this protection means, (1) AGC circuit (
(2) Pad control circuit (Japanese Patent Publication No. 49-156
No. 43, etc.) are known, but (1) has a relatively complicated AGC circuit, and (2) requires a relay circuit and an external reset signal to control the pad.
It had the following drawbacks. A block diagram of a terminal PB receiver considered to solve these problems is shown in FIG. 1, a part of the detailed circuit of FIG. 1 is shown in FIG. 2, and its operating waveforms are shown in FIG. 3.

The multi-frequency signal input to the input terminal IN is separated into one high group wave and one low group wave 11, 11' by one branching filter, and then
The signal is applied to the limiter circuits 2 and 2', and at the same time, it is also applied to the maximum value detection circuits 3 and 3'. The maximum value of the 1-wave component of the input signal detected here is then input to the variable threshold circuits 4, 4', and is compared with the lowest level (fixed threshold) VF to be received, to first determine whether it is the level to be detected or not. After checking, if the level is to be detected, a threshold value that is attenuated by the necessary amount than the previously detected maximum value is applied to the detection terminals of limiters 2 and 2', and if the level is not to be detected, it is fixed. Apply threshold value VF. On the other hand, limiter circuit 2, 2
The other end of 5 is one wave 11 of the input signal from the splitter filter 1.
, 11' has arrived, the limiter circuit compares the levels applied to both terminals, and determines the level applied to the detection level generation terminal (output level of variable threshold circuits 4, 4': 12, 12'). Limiter circuit 2 only when exceeding
, 2' output square waves 13, 13', and the output 13
, 13' select the applied signal by the bandpass filter circuit 5, and the level detection circuit 6 determines whether the frequency is to be detected, and then the output circuit 7 determines whether or not to output it. It is checked and outputs are generated at the corresponding terminals of outputs 0UT1-8. Here, a protection method when an echo signal component arrives will be explained using FIGS. 2 and 3. The output of the demultiplexing filter 1 is applied to 11 in FIG. 2, and the maximum value of the applied input signal is applied to the capacitor C in the maximum value detection circuit 3. is charged and stored. Also, this maximum value is the time constant C. - It is maintained at a level higher than the level due to the echo component for a time determined by (RO+R1).
At the same time, the maximum value is attenuated by a ratio determined by R, ARO+R1) and is subsequently applied to the variable threshold circuit 4.
On the other hand, the variable threshold circuit 4 includes an operational amplifier 9 and a diode D1.
The maximum value detection circuit 3 is
The output level PHIN is compared with a fixed threshold value VF, and the dominant level 12 is applied to one terminal of the limiter circuit 2 constituted by an operational amplifier 10. The output of the demultiplexing filter 1 applied from 11 is added to the other one terminal, and the PHI
This level 12 compared to the dominant level 12 of N or F
A rectangular wave output 13 is obtained only when the input signal level exceeds . FIG. 3 shows the waveforms of each part, 11 is the output waveform of the branching filter 1, and 12 is the output waveform of the variable threshold circuit 4. Also, 1
3 is the output waveform of the limiter circuit 2. It is clear from FIG. 3 that the duty of this rectangular wave is less than 50%, and there is a drawback that a waveform with a duty of 50e cannot be obtained. Therefore, it is clear that the alternating current component of this rectangular wave is smaller than the duty of 50%, and there is a drawback that the subsequent detection operation does not operate normally. For general explanation of these receivers, please refer to Japanese Patent Publication No. 39-207
It is described in Publication No. 51 "Multi-Frequency Signal Receiver". Further, in FIG. 3, A indicates a normal input signal, and B indicates each part of an echo signal. SUMMARY OF THE INVENTION An object of the present invention is to provide a signal receiver that eliminates the drawbacks of the prior art described above, prevents the influence of echoes with a simple circuit, and can obtain a rectangular wave with a duty of 50%.

In order to achieve the above object, the present invention includes a second limiter circuit that converts an input signal into a rectangular wave signal with a duty of 50% and outputs the signal, and a first limiter circuit that receives an input signal according to the maximum level of the input signal. A circuit is provided to rectify the output signal of the circuit, the output signal of the rectifier circuit is ANDed with the output signal of the second limiter circuit, and the AND output is applied to the bandpass filter. be.

FIG. 4 is a block diagram showing one embodiment of the present invention, and the present invention will be explained in detail below with reference to the drawings.

In FIG. 4, the same blocks as those in FIG. 1 are given the same numbers. In the figure, 14, 14' are rectifier circuits, 1
5 and 15' are limiter circuits, and 16 and 16' are AND circuits. After the multi-frequency signal applied to the input terminal 1N is separated into high group and low group frequencies 11 and 11' by the splitter filter 1, a rectangular wave signal with a duty of 50% is obtained. It is applied to the limiter circuits 15, 15'. On the other hand, the output of the splitter filter 1 is connected to the limiter circuits 2 and 2' and 3
, 3' are applied to the maximum value detection circuit. The outputs of the variable threshold circuits 4 and 4' are 12 as explained in FIGS. 1 to 3 above.
, 12' are obtained, and these outputs 12, 12' are applied to the limiter circuits 2, 201 ends.

In the limiter circuits 2 and 2', these outputs 12 and 12
' and outputs 11, 1V of the demultiplexing filter 1 are compared to obtain outputs 13, 13' corresponding to normal input signals. The outputs 13, 13' are applied to rectifier circuits 14, 14' to obtain rectified outputs 17, 17'. These outputs 17, 17' are only the output of the normal input signal part, and the outputs 17, 17'
' is added to one end of the AND circuits 16, 16', and a limiter circuit 15, 15/ is added to the other end of the AND circuits 16, 16'.
By applying the outputs 18, 18' and performing a logical product, a rectangular wave pulse with a duty of 50% can be obtained from the AND outputs 19, 19', and the above-mentioned drawback can be eliminated.
A specific example of a real tumor is shown in FIG. 5, and its #chii waveform is shown in FIG.

The output of the branching filter 1 is added to 11 in FIG. 5, and is applied to a limiter circuit 15 comprising an operational amplifier 20 and resistors R3 and R4. The output waveform 18 of this limiter circuit 15 is shown in FIG. It is also applied to the input terminals of the limiter circuit 2 of the operational amplifier 10 and the maximum value detection circuit 3 of the operational amplifier 8, and the maximum value potential of the input signal 11 is applied to the capacitor C. is charged and stored. Also, this maximum value is the time constant C. - It is maintained at a level higher than the level caused by the echo signal for a time determined by (RO+R1). At the same time, the maximum value is attenuated by a ratio determined by R1/(RO+R1) and applied to the subsequent variable threshold circuit 4. On the other hand, the variable threshold circuit 4 compares the output level PHIN from the maximum value detection circuit 3 with the fixed threshold VF by a comparison circuit constituted by an operational amplifier 9 and a diode D1, and selects the dominant level from the operational amplifier constituting the limiter circuit 2. Output to the negative terminal of 10. The output waveform 12 is shown in FIG. A comparison circuit 1 compares this level 12 with the branching filter output level 11.
Compare with 0. The output waveform 13 of the limiter circuit 2 is shown in FIG. If this output 13 is applied to a rectifier circuit 14 composed of capacitors Cl and C2, a diode D2, resistors R5 and R6, and an operational amplifier 21, the output 17 will have the output waveform shown in FIG. Note that V1 is a DC power supply for operating the operational amplifier 21, and is a comparison voltage with a rectified output. In order to AND the output 17 and the limiter output 18, it is added to an AND circuit 16 consisting of a diode D3 and a resistor R7. 19 shows the output waveform of the AND circuit.

As described above, according to the circuit configuration according to the present invention, the echo signal B can be protected and a rectangular wave output 19 with a duty of 50% can be obtained. As described above, according to the present invention,
Echo signals can be protected economically with a simple circuit configuration, and a square wave output with a duty of 50% can be obtained.

In the above practical example, a case was described in which a two-frequency mixed multi-frequency signal was received, but the present invention is not limited to this, and for example, a single-frequency signal that does not require a splitting filter. Needless to say, this can also be applied to reception.

Further, it goes without saying that a maximum value detection circuit, a variable threshold value circuit, etc. can be provided commonly to each group.

[Brief explanation of the drawing]

Figure 1 is a block diagram of the considered signal receiver, Figure 2
The figure is a detailed circuit diagram of a part of FIG. 1, FIG. 3 is an operation waveform diagram of each part in FIG. 2, FIG. 4 is a block diagram showing one embodiment of the present invention, and FIG. A detailed circuit diagram of each part, FIG. 6 is an operation waveform diagram of each part in FIG. 1... Branch filter, 2, 2', 15, 15'.
...Limiter circuit, 3,3t...Maximum value detection circuit, 4,4'...Variable threshold circuit, 5...
...Band filter circuit, 6...Level detection circuit,
7... Output circuit, 8, 9, 10, 20, 21.
...Operation amplifier, 14... Rectifier circuit, 1
6...AND circuit, 11, 12, 13, 17,
18, 19... Signal.

Claims (1)

[Claims] 1. A signal receiver that receives and identifies an input signal according to its frequency, which includes a first limiter circuit that operates according to the signal level of the input signal, and a second limiter that outputs the input signal as an output signal with a duty of 50%. a maximum value detection circuit that detects the maximum value of an input signal; a variable threshold circuit that varies the detection level of the first limiter circuit according to an output level of the maximum value detection circuit; and the first limiter. A rectifier circuit that rectifies the output signal of the circuit, and an AND circuit that ANDs the output signal of the rectifier circuit and the output signal of the second limiter circuit are provided, and the output signal of the AND circuit is A signal receiver characterized in that a signal in a predetermined frequency band is received by applying the signal to a bandpass filter.