JPS6163167A - Sound multiplex signal processing device - Google Patents

Abstract

PURPOSE:To remove disturbing signals of 2Hf component added to sound multiplex signals by producing signals twice horizontal repetitive frequency from a horizontal synchronizing signal or fly-back pulse and adding the signal to the adder of a demodulating circuit of sub-sound signal. CONSTITUTION:A horizontal repetitive signal input is supplied to the 2fH generating circuit 4 of a sound multiplex signal processing device, and a 2fH signal phase locked to the input signal is generated from a 2fHPLL circuit 7. The phase and amplitude of the 2fH signal from the circuit 7 are processed by a phase adjusting circuit 5 and an amplitude adjusting circuit 6, and adjusted so as to shift by 180 deg. from the 2fH disturbing wave signal and to the same amplitude and applied to an adder 3. Sound multiplex signals are applied to another terminal of the adder 3 through a BPF1, and added to the 1Hf signal from the 2Hf generating circuit 4, and output of the adder 3 is demodulated by a sub-sound demodulating circuit 2. Thus, disturbing signals of 2Hf component added to sound multiplex signals are removed, and sound multiplex signals are demodulated satisfactorily.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an audio multiplex signal processing device for a color television receiver.

Configuration of a conventional example and its problems A block diagram of a sub-audio circuit of a conventional audio multiplex signal processing device is shown in FIG.

In FIG. 1, numeral 1 denotes a bandpass filter whose characteristics are shown in FIG. 2. 2 is a sub-audio demodulation circuit. Next, the operation of this circuit will be explained.

First, the sub-audio of the audio multiplexed signal is FM-modulated, and after unnecessary components are removed by a band-pass filter 1, it is FM-demodulated by a sub-audio demodulation circuit 2.

The center frequency of the sub-sound is selected to be twice the horizontal frequency fH of the television receiver, and the bandpass filter 1 is set to double the horizontal frequency fH of the television receiver.
A trap is inserted at the frequency of 3xfH as shown in FIG.

However, the harmonics of the horizontal repetition signal also include a second-order component, and this second-order harmonic component passes through a bandpass filter, is FM demodulated, and has the disadvantage of outputting an interference signal generally called a buzzbeat. I had (・ta.

OBJECTS OF THE INVENTION The present invention aims to eliminate the above-mentioned drawbacks and provide an audio multiplex signal processing device that is not affected by the second harmonic of a horizontally repeated signal.

Structure of the Invention The present invention creates a signal with twice the horizontal repetition frequency (hereinafter referred to as 2fH) from the horizontal periodic signal or flyback pulse signal of a television receiver, and demodulates the 2fH signal into a sub-audio signal. It is connected to the other input of the adder provided on the input side of the circuit, and the 2fH signal is generated by the 2fH signal phase adjustment and amplitude adjustment circuit provided in the 2fH signal generation circuit.
By adjusting the phase and amplitude of the signal, it is possible to remove the 2fH component contained in the input signal of the sub-audio signal demodulation circuit.

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

In FIG. 3, numerals 1 and 2 are the same bandpass filter and sub-audio demodulation circuit as in FIG. 1. Reference numeral 3 denotes an adder, which is provided before the sub-audio demodulation circuit 2. Furthermore, this adder 3
may be placed before the bandpass filter 1. 4 is a 2fH signal that generates a 2fH signal that is twice the horizontal repetition frequency as the horizontal synchronization signal or flyback signal.
This circuit includes a phase adjustment circuit 5. It includes an amplitude adjustment circuit 6 and a 2fHPLL circuit 7, which will be described later.

7 is a 2f HPLL circuit which generates a 2f'H signal whose phase is locked from a horizontal repetition signal and uses a PLL system.

The operation of this embodiment configured as above will be described below.

First, when a horizontal repetition signal is input to the 2fH generation circuit 4, the 2fHPLL circuit 7 generates a 2f'H signal whose phase is locked to this input signal. 2f included in audio multiplex signal
The phase and amplitude of the ``H interference signal differs depending on the arrangement of the circuits in the television receiver and the routing of the wiring, so in order to cancel this, the phase and amplitude of the 2f'H signal generated in the 2f HPLL circuit 7 are changed. The phase adjustment circuit 5 and the amplitude adjustment circuit 6 adjust the phase of the 2fH interference signal by 18 degrees and the same amplitude, and add the signal to the adder 3, demodulate it in the sub-audio demodulation circuit 2, and output it.

In this way, the 2fH interference signal contained in the audio multiplex signal can be removed.

Effects of the Invention As described above, the present invention has the advantage that the 2fH signal contained in the audio multiplex signal
A 2fH interference signal can be generated by generating a signal with a phase shift of 180° and the same amplitude from the horizontal repetition signal and adding it to the audio multiplex signal.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a sub-audio circuit of a conventional audio multiplex signal processing device, FIG. 2 is a frequency characteristic diagram of the same bandpass filter, and FIG. 3 is a sub-audio circuit diagram of a conventional audio multiplex signal processing device of an embodiment of the present invention. FIG. 2 is a block diagram of an audio circuit. 1...Band pass filter, 2...
Sub-audio demodulation circuit, 3... Adder, 4...
・2fH signal generation circuit, 5... phase adjustment circuit,
6... Amplitude adjustment circuit, 7...2fHP
LL circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person ¥1
Figure 2 Figure 3

Claims (1)

[Claims] A sub-audio demodulation circuit that demodulates a sub-audio signal in an audio multiplex signal, and an adjustment circuit that varies the phase and amplitude of a horizontal repetition signal with twice the horizontal repetition frequency whose phase is locked by a horizontal synchronization signal or a flyback pulse signal. and an adder for adding the sub-audio signal and the output signal of the adjustment circuit, the horizontal repeat signal included in the sub-audio signal being varied by varying the phase and amplitude of the double horizontal repeat signal. 2
An audio multiplex signal processing device that cancels interfering signals of harmonics.