JPS6057784B2 - Phase pulse signal regeneration method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for reproducing a phase pulse signal in a facsimile receiver or the like.

Conventionally, facsimile receivers perform the following steps in order to match the phase with the transmitting side during the phase signal period before transmitting the image signal.
The incoming phase pulse signal must be regenerated.

However, since the signal arriving at the facsimile receiver passes through the line, it is affected by the line, resulting in distortions and the like, making it impossible to reproduce a proper phase pulse signal. Figure 1 shows the phase pulse signal a transmitted from the transmitting side.
, the phase pulse signal arriving at the receiving side, the phase signal c after being detected by the wave detector, and the regenerated phase pulse signal d. e is a carrier wave, which is omitted from the middle. The wavy line f indicates the slice level.
The phase pulse signal a transmitted from the transmitting side is distorted due to the influence of the line, and when it arrives at the receiving side, it becomes a phase pulse signal. When this is detected by a wave detector, it becomes a phase pulse signal c, and this signal c is set at an appropriate slice level f.
When compared using a comparator or the like, a phase pulse signal d is reproduced. In this way, the phase pulse signal d reproduced on the receiving side becomes completely different from the phase pulse signal a transmitted from the transmitting side due to the influence of the line. When this phase pulse signal d is used, the facsimile receiver misunderstands that two phase signals have arrived in succession in a short period of time, causing malfunction. Therefore, even if the line has poor characteristics,
How to reproduce a phase pulse signal has been a technical problem for a long time. Generally, it has been known to provide a bandpass filter in order to correct the distortion of the phase pulse signal shown in FIG.

In other words, if a bandpass filter is provided in front of the detection circuit in the example shown in FIG. 1, a signal as shown in FIG. 2 will be generated at its output, and the distortion can be corrected. This is because the bandpass filter has the characteristics shown in Figure 3, so the overshoot parts A and A' can be removed.However, simply providing a bandpass filter is not appropriate.In other words, the input This is because bandpass filters have the characteristics of attenuating the voltage level of a signal or delaying a signal, which may conversely distort a normal image signal. This was done in view of the above drawbacks, and in facsimile receiving equipment that is equipped with multiple amplitude equalizers with different degrees of equalization to improve image quality and switches between them depending on the line condition, By forcibly selecting the amplitude equalizer with the maximum degree of equalization among the plurality of amplitude equalizers, distortion of the phase signal due to the influence of the line is removed, and However, it is an object of the present invention to provide a phase pulse signal reproducing method that can reliably reproduce a phase pulse signal.

The present invention was made by focusing on the fact that an amplitude equalizer has operating characteristics equivalent to a bandpass filter.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 4 is a block diagram of a main part of a facsimile receiver according to an embodiment of the present invention. In the figure, 1 is an input terminal, and all signals transmitted from the transmitting side are input to the facsimile receiver from this terminal. 2a-2c
are amplitude equalizers, but each has a different degree of equalization.

Here, the magnitude relationship of the equalization degrees of these amplitude equalizers is 2a
<2b minus 2c. The characteristics of the equalization degree of this amplitude equalizer are as shown in FIG. 5, which is similar to the characteristics of a bandpass filter. What is important here is that both bandpass filters and highpass filters tend to remove low frequency components. In other words, signal distortion due to line distortion can be treated as a low frequency component. A switch 3 selects one of the amplitude equalizers 2a to 2c according to the output signal h of the control circuit 10.

If the output signal h is a 2-bit signal, the signal h
The relationship between the selected amplitude equalizer is as shown in Table 1.
The mechanism of this relationship can be easily created using conventional known techniques. The amplitude equalizers 2a-2c and the switch 3 and part of the control circuit form an automatic amplitude equalizer.

This automatic amplitude equalization device is, for example,
I-Elm 1i-HtL-Sanojo groan μ! Control circuit 1 using the signal passing through the feedback loop in AGC circuit 4
0 detects the line status, and control circuit 1 responds to the line status.
0 operates switch 3 to designate the optimum amplitude equalizer. Note that if the line condition is very good, the amplitude equalizer is not necessary, so the selection of switch 3 is as follows:
A model without an equalizer has also been added. 4 is an AGC circuit that automatically controls the gain so that its output has a constant voltage level no matter what voltage level signal is input; 5 is an AGC circuit that controls the operation according to a control signal from the control circuit 10; A demodulation circuit whose start and end etc. are controlled, 6 is a demodulation circuit 5
This is a recording circuit that performs recording based on the demodulated signal output from the.

7 is a detection circuit, and 8 is a comparison circuit. By comparing the signal inputted from the detection circuit 7 and the constant voltage level signal inputted from the terminal 9, a phase pulse signal is reproduced.

10 is a control circuit containing a microcomputer, which controls the entire mechanism of the facsimile receiver;
It also controls each circuit. Here, phase matching is also performed using the regenerated phase pulse signal output from the comparator 8. Next, a method for reproducing a phase pulse signal in the facsimile receiver having the above configuration will be explained.

First, the control circuit 10 operates the switch 3 using the signal h from the end of the image signal section of the previous communication until just before the start of the phase signal section of the current communication, and forces the switch 3 to obtain the highest degree of equalization. The amplitude equalizer 2c is selected and the signal h is not changed during the phase signal section. In the example in Table 1, the signal h is (1.1
). As mentioned above, the amplitude equalizer performs the same operation as a high-pass filter, and since the amplitude equalizer 2c with the highest degree of equalization is selected, the amplitude equalizer 2c as shown in FIG. It also has great operating characteristics as a high-pass filter. Therefore, since the phase signal arriving at the input terminal always passes through the amplitude equalizer 2c, distortion of the phase signal that occurs while passing through the line can be reliably corrected no matter what state of the line.

Furthermore, since the amplitude equalizer 2c operates in the same manner as a high-pass filter, the voltage level at its output is somewhat attenuated; however, the amplitude equalizer 2c is located before the AGC circuit 4;
Detection circuit 7 and comparison circuit 8 for reproducing phase pulse signals
is located after the ACC circuit 4, so even if the voltage ν of the phase signal is attenuated by the amplitude equalizer 2c, the AGC circuit 4 guarantees the amount of attenuation. has no adverse effect. Furthermore, although the amplitude equalizer outputs the signal with a slight delay, there is no problem because it is configured to show the same amount of delay no matter which option the switch 3 selects. . Next, the control circuit 10 performs phase matching using the re-outputted phase pulse signal output from the comparison circuit 4, and after completing the phase matching, releases the fixation of the signal b.

Thereby, the automatic amplitude equalizer detects the original line condition and selects an appropriate amplitude equalizer according to the line condition. Therefore, in the image signal section after the phase signal section, over-equalization will not occur and the image signal will not be adversely affected. As described above, according to the present invention, a plurality of amplitude equalizers with different degrees of equalization are provided,
It is equipped with an automatic amplitude equalizer that selects an amplitude equalizer suitable for the line condition from among these multiple amplitude equalizers, and uses the maximum degree of equalization among the automatic amplitude equalizers in the phase signal section. By forcibly selecting the amplitude equalizer that has an amplitude equalizer and removing the forced selection after phase matching, signal distortion due to the influence of the line can be corrected, and there will be no adverse effect on the image signal. The phase pulse signal can be reproduced without any noise.

[Brief explanation of drawings]

Figures 1A, b, c, and d are signal waveform diagrams explaining the conventional method for reproducing phase pulse signals, Figure 2 is a waveform diagram showing the output signal of the bandpass filter, and Figure 3 is the characteristic of the bandpass filter. 4 is a block diagram of essential parts showing an example of a facsimile receiver implementing the method of the present invention,
FIG. 5 is a characteristic diagram of the amplitude equalizer. 1...Signal input terminal, 2a-2c...Amplitude equalizer, 3...Switch, 4...A
GC circuit, 5... Demodulation circuit, 6... Recording circuit, 7... Detection circuit, 8... Comparison circuit, 9
... Constant voltage input terminal, 10... Control circuit.

Claims (1)

[Claims] 1 It has a plurality of amplitude equalizers with different degrees of equalization, and has a function of selecting an amplitude equalizer suitable for the line condition from among the plurality of amplitude equalizers, The phase pulse signal is regenerated by forcibly selecting an amplitude equalizer having a maximum degree of equalization among the amplitude equalizers of the above, and the forced selection is canceled after phase matching. How to play the signal.