JPS6395717A - Signal receiving circuit - Google Patents

Abstract

PURPOSE:To prevent the generation of a digital signal from an irregular bipolar signal due to noise or the like by providing a lower limit on a threshold voltage in generating a digital signal through the comparison between the rectified bipolar signal voltage and the threshold voltage changing in response to the voltage. CONSTITUTION:A regulating voltage of a prescribed level generated by a level setting means 4 is fed to a threshold value generating circuit 3, compared with a threshold voltage changing in proportion to the bipolar signal voltage generated from the circuit 3 and rectified, and either higher voltage is outputted as a threshold voltage. Thus, the threshold voltage is not less than the regulated voltage. Since the regulated voltage is set higher than the output voltage of a rectifier circuit 1 receiving a bipolar signal of a minute level due to crosstalk or the like, even if the bipolar signal of a minute level due to crosstalk of the like is received. the output voltage of the rectifier circuit 1 is below the threshold voltage and a comparator 2 does not generate the digital signal. which compares the output voltage of the rectifier circuit 1 and the threshold voltage.

Description

[Detailed Description of the Invention] [Summary] In a signal receiving circuit, when generating a digital signal by comparing the voltage of a rectified bipolar signal and a threshold voltage that changes in accordance with the voltage, a threshold value is determined. A lower limit is set on the value voltage to prevent a digital signal from being generated from an irregular bipolar signal due to noise or the like.

[Industrial application field]

The present invention relates to improvements in signal receiving circuits used in digital subscriber circuits of digital exchanges and the like.

Bipolar signals sent from digital telephones, etc. are received by the signal receiving circuit of the digital subscriber circuit, converted to digital signals, and sent to the exchange side. However, if the received signal stops, the signal at a minute level due to crosstalk etc. There is a need to provide a signal receiving circuit that does not operate with very small level signals because the signal may be mistakenly converted into a digital signal.

[Conventional technology]

FIG. 3 is a signal receiving circuit diagram of a conventional example, and FIG. 4 is a voltage waveform explanatory diagram of the main part of FIG. 3.

Since the bipolar signal sent from a digital telephone etc. passes through a filter etc., at the input point a of the rectifier circuit 1, the voltage waveform as shown in Fig. 4(a) is received by the rectifier circuit 1, and the rectified output is The voltage waveform shown in FIG. 4(b) is now sent to the comparator 2.

The output of the rectifier circuit 1 is also sent to the peak value detection circuit 31,
The peak voltage of the output is detected, and at point C, as shown in Fig. 4(c)
A voltage waveform like this is output.

The amplifier 32 amplifies the output of the peak value detection circuit 31 so that the output becomes a voltage % of the peak voltage, and charges the capacitor C via the diode D. Therefore,
The voltage at point d becomes two times the peak voltage as shown in FIG. 4(d), and a threshold voltage is generated that changes in accordance with the bipolar signal voltage.

Comparator 2 compares the voltage waveform at point d with the threshold voltage at point d, determines whether the received signal is ``0'' or ``1'', and generates a digital signal at point e as shown in Figure 4(e). do.

[Problem that the invention seeks to solve]

In the conventional signal receiving circuit, the threshold voltage for determining the sign "0" or "1" of the rectified bipolar signal is
Varies depending on the received bipolar signal voltage. Therefore, if a micro-level bipolar signal due to crosstalk or the like is received when a normal received signal has stopped, the threshold voltage will correspondingly decrease, and the exchange will consider it to be a normal signal and generate a digital signal. There are problems that can cause it to malfunction.

[Failure to solve the problem]

FIG. 1 is a block diagram of the principle of the present invention.

In the figure, 1 is a rectifier circuit that rectifies a bipolar signal;
3 is a threshold generation circuit that generates a threshold voltage that changes according to the output voltage of the rectifier circuit 1; 2 is a threshold generator that generates a digital signal by comparing the output voltage of the rectifier circuit 1 and the threshold voltage; It is a comparator.

4 relates to the present invention and generates a regulated voltage of a certain level,
This is level setting means for applying the voltage to the threshold generation circuit 3. This measure solves the problem.

[Effect]

The constant level regulation voltage generated by the level setting means 4 is applied to the threshold generation circuit 3 and compared with a threshold voltage that changes in proportion to the rectified bipolar signal voltage generated by the circuit. , whichever is higher is output as the threshold voltage.

Therefore, the threshold voltage never becomes lower than the regulation voltage.

The regulated voltage is set higher than the output voltage of the rectifier circuit 1 that has received a minute level bipolar signal due to crosstalk, etc., so even if a minute level bipolar signal due to crosstalk or the like is received, the output voltage of the rectifier circuit 1 is The voltage is below the threshold voltage, and the comparator 2 that compares the output voltage of the rectifier circuit 1 with the threshold voltage considers it to be a normal signal and does not generate a digital signal.

A digital signal is generated at the very small level of Pai Borai No. 3 due to crosstalk, etc., and the switching equipment will no longer malfunction.

〔Example〕

The present invention will be specifically explained below with reference to illustrated examples.

FIG. 2 shows a signal receiving circuit according to one embodiment of the present invention. The same reference numerals refer to the same objects throughout the design.

In FIG. 2, resistors R1, R2, and R3 correspond to the level setting means 4 in FIG.

In FIG. 2, the voltage created by resistors R1 and 112 charges a capacitor C via a resistor R3 to maintain a regulated voltage at a constant level.

The regulated voltage is set higher than the output voltage of the rectifier circuit 1 that has received a minute level bipolar signal due to crosstalk or the like.

When a minute level bipolar signal is received, the output voltage of the rectifier circuit 1 is determined by the peak value detection circuit 31 and amplifier 3.
2, a threshold voltage that changes depending on the bipolar signal is created, but since it is lower than the above-mentioned regulation voltage, the regulation voltage is used as the threshold voltage.

Therefore, even if a very small level bipolar signal is received, the comparator 2 will make a determination of "0", and no erroneous digital signal will be generated.

When a normal bipolar signal is received, the threshold voltage created by the peak value detection circuit 31 and amplifier 32, which changes according to the bipolar signal voltage, is descended from the regulation voltage, so the threshold voltage is used to The comparator 2 determines whether the received signal is ``0'' or ``1'' and generates a digital signal.

〔Effect of the invention〕

As explained above, in the present invention, even if a minute level bipolar signal such as crosstalk is received, the signal receiving circuit considers it to be a normal signal and does not generate a digital signal, thereby preventing malfunction of the exchange. (There is an effect.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the principle of the present invention, Fig. 2 is a signal receiving circuit diagram of an embodiment of the present invention, Fig. 3 is a signal receiving circuit diagram of a conventional example, and Fig. 4 shows the main parts of Fig. 3. It is a voltage waveform explanatory diagram. In the figure, 1 is a rectifier circuit, 2 is a comparator, 3 is a threshold generation circuit, and 4 is a level setting means.

Claims (1)

[Claims] A rectifier circuit (1) that receives and rectifies a bipolar signal;
a threshold generation circuit (3) that generates a threshold voltage that changes depending on the output voltage of the rectification circuit (1); and an output voltage of the rectification circuit (1) and the threshold generation circuit (3). In a signal receiving circuit consisting of a comparator (2) that generates a digital signal by comparing the voltage with a threshold voltage of A signal receiving circuit characterized in that a level setting means (4) is provided, and the threshold voltage outputted from the threshold voltage generation circuit (3) is prevented from becoming lower than the regulation voltage.