JPS59133779A - Picture receiving system - Google Patents

Abstract

PURPOSE:To reduce the low frequency noises through a simple constitution by detecting the level fluctuation of a low frequency from the horizontal synchronizing signal of a received picture signal and then superposing the detection output on the original signal at the rear stage side of a picture receiving part. CONSTITUTION:The picture signal at the transmission side arrives at the reception side with the fluctuation generated from a horizontal synchronizing signal by the low frequency noises to the reference level of a picture signal. The horizontal synchronizing signal is extracted from said picture signal by a reproducing circuit HSR for horizontal synchronizing signal. Then only the horizontal synchronizing signal component is extracted from the arrived reception wave by a horizontal synchronizing level detecting circuit HSL. This horizontal synchronizing signal is transmitted through an LPF to obtain a signal having a smooth waveform. This signal is converted into an adverse phase and then synthesized with the received signal through a synthesizing circuit LMB. Thus the fluctuation at a part corresponding to a low frequency noise is corrected to obtain a signal free from noises at an output terminal OUT. It is possible to combine a signal phase inverting circuit and the circuit CMB into a differential amplifier.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to an image receiving system that reduces the influence of noise in an image signal transmission system.

(2) Prior art and problems In general, in millimeter wave band signal transmission systems, it has been found that noise generated by local oscillators used on the transmitting and receiving sides has a large effect on the quality of transmitted signals.

Therefore, especially when transmitting an image signal, the signal level may fluctuate due to the influence of noise from the power supply circuit, and the image may appear shaky. Conventionally, it was possible to escape from this influence by inserting a signal clamp circuit inside the receiver, but
There are problems when using it within a communication channel. That is, since the clamp circuit operates as a DC component regeneration circuit, discontinuous signal changes occur.

It has also been proposed to detect the peak voltage on the horizontal synchronizing signal side and apply feedback, but this method has the disadvantage of malfunctioning due to impulse noise.

(3) Purpose of the Invention The purpose of the present invention is to improve the above-mentioned drawbacks and to make it applicable to communication channels, and to provide an image receiving method that uses a horizontal synchronization signal and reduces the influence of noise in an image signal transmission system. It is about providing.

(4) Structure of the Invention The structure of the present invention to achieve the above-mentioned object is that in an image receiving method in which a wirelessly transmitted modulated image signal is received and demodulated on the receiving side to obtain an original image signal, the horizontal direction of the received image signal is A circuit for detecting a level fluctuation signal having a lower frequency than the horizontal synchronizing signal from the synchronizing signal, and a circuit for detecting a level fluctuation signal lower than the horizontal synchronizing signal from the horizontal synchronizing signal of the detected image signal. The method is to include a circuit that superimposes the signal on the original signal.

(5) Embodiment of the invention FIG. 1 is a diagram showing the configuration of the first embodiment of the invention, where IN is an image signal input terminal, ) (SR is a horizontal synchronizing signal reproducing circuit,
-HS L indicates a horizontal synchronization level detection circuit, LPF indicates a low-pass filter, CMB indicates a synthesis circuit, and OUT indicates a signal output terminal. The signal waveforms of each part are shown in FIG. 2, with prefixed numbers corresponding to each other. In Fig. 2, the image signal on the transmitting side, that is, the signal that has undergone noise removal processing on the receiving side, is shown as ■.The reference level of the image signal may fluctuate due to low frequency noise, for example, several kHz, which is lower than the horizontal synchronization signal. The signal is generated and reaches the receiving side (see Fig. 2 (■)). From this signal, only the horizontal synchronizing signal is extracted by the horizontal synchronizing signal reproducing circuit H3R as shown in FIG. Next, the horizontal synchronization level detection circuit H3L extracts only the horizontal synchronization signal part from the incoming received wave, and
Obtain figure ■. This signal is passed through a low-pass filter LPF to obtain a signal (2) with a smooth waveform, which is then converted into an inverse phase signal and combined with the received signal in a combining circuit LMB. As a result, fluctuations in the portion corresponding to low frequency noise can be corrected, and a noise-free signal can be obtained at the output terminal OUT.

In addition, in Fig. 1, the signal phase inversion circuit and the synthesis circuit CMB
may be collectively used as a differential amplifier.

FIG. 3 is a block diagram of a second embodiment of the present invention.

Although FIG. 3 differs from FIG. 1 in that it is of a feed bank type, the same reference numerals indicate similar parts.

In FIG. 3, H is a hybrid circuit that branches signals, and BPF is a band pass filter that does not pass signals of extra frequencies and returns only a predetermined signal to the signal input side and guides it to the operational amplifier OPA.

Therefore, stable operation and noise reduction can be achieved. Further, the waveforms of each part correspond to the prefixed numbers shown in FIG.

In Figure 3, an operational amplifier OPA is inserted into the signal circuit, and a feedback signal is applied to its input terminal, so the residual noise signal can be reduced to almost zero, and the effect of removing the effects of noise is greater than in the case of Figure 1. Remarkable.

FIG. 4 shows the configuration of a third embodiment of the present invention. Since waveform distortion is a problem in the image signal transmission system, a low-pass LPF is used as the filter, a DC offset voltage vO is applied, and the feedback signal level is adjusted by the operational amplifier 0PA2. Therefore, the operational amplifier 0PAI of the main transmission system can operate with less distortion, which is effective in a digital signal transmission system.

(6) Effects of the Invention As described above, according to the present invention, low frequency noise caused by local oscillators and the like can be reduced with a simple configuration, and a clear received image can be easily obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of the first embodiment of the present invention, FIG. 2 is a signal waveform diagram explaining the operation of FIG. 1, and FIG. 3 is a diagram showing the configuration of the second embodiment of the present invention. FIG. 4 is a diagram showing the configuration of a third embodiment of the present invention. IN-・Image signal input terminal. HSR-Horizontal periodic signal regeneration circuit. H3L--Horizontal cycle level detection circuit. LPF--Low pass filter. CMB...Synthesis circuit. OUT...Signal output terminal. H-Hybrid circuit. 0PA--Operation amplifier. BPF ---Band pass filter. Vo... - Offcent voltage patent applicant Fujitsu Limited agent Patent attorney Eisuke Suzuki

Claims (1)

[Claims] 1. In an image receiving method in which a wirelessly transmitted modulated image symbol is received and demodulated on the receiving side to obtain an original image signal, a level of a frequency lower than the horizontal synchronizing signal from a horizontal synchronizing signal of the received image signal is determined. An image receiving system comprising: a circuit for detecting a fluctuation signal; and a circuit for superimposing the output of the detecting circuit with an original signal at a downstream side of an image receiving section. 2. In an image receiving system in which a wirelessly transmitted modulated image signal is received and demodulated on the receiving side to obtain an original image signal, a circuit that detects a level modulation signal having a lower frequency than the horizontal synchronization signal of the received image signal from the horizontal synchronization signal. and a circuit for superimposing the output of the detecting circuit at an input stage of an image receiving section.