JPS5840676Y2 - receiving circuit - Google Patents

Description

[Detailed Description of the Invention] Generally, in a terminal device that receives data via a long transmission line, various malfunctions occur due to noise mixed into the received signal.

The present invention relates to a receiving circuit applied to a terminal device in such a field that requires means for enhancing noise resistance.

A conventionally used method is to insert a noise filter.

This method is extremely simple and can be expected to be quite effective, so it is thought that it will be used frequently in the future, but as the signal transmission speed increases, problems arise in terms of responsiveness.

In addition, as another method, various methods have been proposed in which a time width T is set sufficiently shorter than the minimum pulse width of the signal, and pulses having a time width smaller than T are ignored.

Although this method is also very effective, it cannot be applied when the pulse width of the mixed noise is wide.

Therefore, in the case where the received signal level can be expected to be relatively large, the present invention aims to eliminate the noise mixed in the received signal by setting a low-level mixed noise level compared to the signal level. The purpose is to realize the circuit.

According to the present invention, two signals having mutually opposite phases are extracted from a received signal.

When these opposite phase signals are used as an A signal and a B signal, the A signal is applied to the first amplifier and the B signal is applied to the second amplifier.

1st. The second amplifier operates in response to an input signal exceeding its own threshold value, and does not operate in response to an input signal below the threshold value (deepened by the bias voltage), resulting in an insensitive region.

1st. The same waveforms having a phase difference of 180° are obtained from the outputs of the second amplifiers, and the signals are shaped by the shaping circuit in the next stage.

FIG. 1 is a block diagram of an embodiment of the present invention, in which 1 is a receiving transformer for receiving signals from a communication line, 2 and 3 are bias circuits, and 3 is marked with an arrow. This shows that the bias voltage can be made variable.

4 and 5 are a pair of amplifiers, and 6 is a shaping circuit.

In this example, a balanced coupling transformer with a secondary winding center tap is used as the receiving transformer 1, a bias voltage is applied to the center tap, both terminals are connected to amplifiers 4 and 5, and the reverse phase signal is output. Here is an example of how to get .

In FIG. 2, A is the waveform applied to the amplifier 4,
B is a waveform applied to the amplifier 5.

7 is a threshold value of each amplifier, and the amplifier is operated by a voltage exceeding this threshold value (shaded area in the figure).

8 is a bias potential. The outputs of amplifiers 4 and 5 are as shown in C and D, respectively, and have different tenity cycles compared to the received waveform, but the shaping circuit 6 at the next stage is a flip-flop, and is set by the signal from amplifier 4, and is set by the signal from amplifier 5. The waveform shown in E can be obtained from the output of the shaping circuit 6.

In Fig. 2, the received signal is expressed as a sine wave, but in general digital data transmission, the signal form is often square wave or pulse waveform, and according to the present invention, the rising and falling edges of the signal are The edge of the signal (
Noise on the rising edge and falling edge is not affected much.

Furthermore, it is highly effective against troubles such as noise that is input only when no signal is being received from the transmission line, inducing malfunctions.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an embodiment of the present invention, and Fig. 2 is a block diagram of an embodiment of the present invention.
It is a figure which showed the waveform of each part of a figure. In the figure: 1...receiving transformer, 2, 3... bias circuit, 4, 5... amplifier, 6...
...Shaping circuit.

Claims (1)

[Scope of utility model registration request] A receiving circuit connected to a transmission line includes a circuit that obtains two signals with opposite phases from the received signal, a pair of amplifiers into which the two signals from the circuit are respectively input, and a circuit that is common to each of the amplifiers. A receiving circuit comprising a bias circuit that provides a bias potential.