JPS62263784A - Sound multiplex signal processor - Google Patents

Abstract

PURPOSE:To prevent a television receiver from receiving the interference due to a flyback pulse by forming the second horizontal synchronizing signal having an opposite phase to the interference signal of the flyback pulse and controlling the phase and an amplitude to cancel the interference signal. CONSTITUTION:The flyback pulse is inputted to the input of a phase circuit 12 as the first horizontal synchronizing signal to adjust the phase and applied to a horizontal synchronizing signal generating circuit 11. The horizontal synchronizing signal generating circuit 11 generates the second horizontal synchronizing signal of substantially the same waveform as the interference signal in a sound multiplex signal, the amplitude is adjusted in an amplitude circuit 10, and the second horizontal synchronizing signal is inputted to one input of an adder 9 disposed at the input side of a PLL circuit 8. The sound multiplex signal is inputted to one input of the adder 9 to cancel the interference signal included in the sound multiplex signal.

Description

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

2. Description of the Related Art In recent years, audio multiplex broadcasting has started in the United States, and television receivers incorporating American audio multiplex processing devices are becoming popular.

An example of the conventional American audio multiplex signal processing apparatus mentioned above will be described below with reference to the drawings.

FIG. 2 shows the configuration of a carrier regeneration circuit of a conventional American audio multiplex signal processing device. FIG. 3 shows the spectrum of a US audio multiplex signal.

As shown in FIG. 3, the American audio multiplex signal consists of a second audio signal called SAP, a stereo broadcasting (L-R) signal, and a (L+R) signal. The (LR) signal is a carrier suppressed AM signal (hereinafter referred to as DSB), and a pilot signal for carrier wave regeneration is inserted at the frequency of the carrier wave bar.

In Fig. 2, 1 is a low-pass filter (hereinafter abbreviated as LPF), 2 is a phase comparator, 3 is a loop filter, 4 is a voltage controlled oscillator (hereinafter abbreviated as VCO), and 5 and 6 are Shio's frequency dividers. , γ is a DSB demodulator.

In the American audio multiplex processing apparatus configured as described above, the audio multiplex signal shown in FIG. Phase comparator 2, loop filter 3, VCO
4. The configuration consisting of frequency dividers 5 and 6 is a standard PLL circuit, and in the case of American audio multiplex processing equipment, the center frequency of vC04 is generally selected to be four times the horizontal repetition frequency (hereinafter abbreviated as fn). ing. One of the signals input to the phase comparator 2 is the (L+R) signal, the (I, -R) signal, and the pilot signal, and the output of the VCO 4 is input to the frequency divider 5, 6 to the other.
Since the frequency-divided signal is added to Kaede, this PL
The L circuit is designed to be phase synchronized with the pilot signal. If the PLL circuit is phase-locked to the pilot signal, the VC
Since the signal obtained by dividing the frequency of the output of O4 becomes the same signal as the carrier wave of the (LR) signal, it is demodulated by the DSB demodulator 7 using this signal, and the (LR) signal is extracted.

Problems to be Solved by the Invention However, with the above configuration, when the American audio multiplex processing device is placed inside a television receiver, interference signals due to flyback pulses are generally included in the audio multiplexed signal. included. In such a case, the frequency of this interference signal is different from that of the pilot signal by several 11z to several 10s2, or the frequency is the same but the phase is not matched, so depending on the degree of the interference signal, the phase synchronization circuit using PLL is activated. Jitter occurs in the phase of the disturbed and regenerated carrier wave, and D
If SB demodulation does not operate correctly or if the interference signal is extremely large, the phase synchronization circuit synchronizes with the interference signal, making demodulation impossible.

In view of the above-mentioned problems, the present invention provides an audio multiplex signal processing device that is less susceptible to interference by flyback pulses of a television receiver.

Means for Solving the Problems In order to achieve this object, the audio multiplex signal processing device of the present invention includes an adder provided on the input side of a circuit for reproducing a carrier wave, and an adder for inputting a first horizontal periodic signal. a circuit that generates a second horizontal periodic signal as a second horizontal periodic signal, and adds a pilot signal to one input of the adder and a second horizontal periodic signal to the other input; A feature is that a phase circuit and an amplitude circuit are provided to control the phase and amplitude of a signal.

Operation With this configuration, a second horizontal periodic signal having an opposite phase to the flyback pulse interference signal entering the pilot signal detection circuit is created from the first horizontal periodic signal, and the phase of the second horizontal periodic signal is Interfering signals can be canceled by controlling the amplitude.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 shows a carrier wave regeneration circuit in an American type audio multiplex signal processing apparatus according to an embodiment of the present invention.

In Fig. 1, 1 is an LPF, 7 is a DSB demodulator, and 8 is a PLL circuit, which is the same as the PLL circuit shown in Fig. 3, which consists of phase comparator 2, loop filter 3, VCO 4, and frequency dividers 5 and 6. It is. 9 is an adder inserted between LPFl and PLL 8, 10 is an amplitude circuit, 11 is a second horizontal periodic signal generation circuit, and 12 is a phase circuit. The flyback pulse is applied to the phase circuit 12, and is further applied as one input signal to the adder 9 through the second horizontal periodic signal generation circuit 11 and the amplitude circuit 1o.

The operation of the audio multiplex signal processing apparatus configured as described above will be described below.

First, the operations of LPF1, DSB demodulator 7, and PLL circuit 8 are the same as in the conventional example shown in FIG.

Next, a flyback pulse is input as a first horizontal periodic signal to the input of the phase circuit 12, and after phase adjustment,
It is added to the horizontal periodic signal generation circuit 11. Then, the horizontal periodic signal generation circuit 11 generates a second horizontal periodic signal having almost the same waveform as the interference signal in the audio multiplex signal, and after the amplitude is adjusted by the amplitude circuit 10, it is placed on the input side of the PLL circuit 8. is added to one input of adder 9. An audio multiplex signal is input to the other input of the adder 9.

As described above, according to this embodiment, a second horizontal periodic signal having almost the same waveform as the interference signal included in the audio multiplex signal is generated in addition to the flyback pulse that is the first horizontal periodic signal, By adjusting the phase J2 amplitude of the second horizontal periodic signal and adding it to the audio multiplex signal, it is possible to cancel the interfering signal contained in the audio multiplex signal.

In this embodiment, the adder 9 is placed on the input side of the PLL circuit 8, but it may be placed on the input side of the LPF1.

Further, since the amplitude circuit 10, the horizontal periodic signal generation circuit 1'1, and the phase circuit 12 are connected in series, their order may be changed. The flyback pulse as the first horizontal periodic signal may be any other horizontal periodic signal as long as it is synchronized with this flybank pulse.

Effects of the Invention As described above, according to the present invention, the adder, the second horizontal periodic signal generation circuit, the phase circuit and the amplitude circuit that adjust the phase and amplitude of the second horizontal periodic signal are used to generate the audio multiplexed signal. It can remove interfering signals, and its practical effects are great.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the configuration of a carrier recovery circuit of an audio multiplex signal processing device according to an embodiment of the present invention, and FIG. 2 is a block diagram of the configuration of a carrier recovery circuit of a conventional audio multiplex signal processing device. FIG. 3 is a spectrum diagram of an audio multiplex signal. 1...LPF, 2...Phase comparator, 3
......Loop filter, 4...VC:O
ls・Old...Frequency divider, 6...Frequency divider, T...
...DSB demodulator, 8...PLL circuit, 9.
...Adder, 10...Amplitude circuit, 11...
...Horizontal periodic signal generation circuit, 12...Phase circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person 1st
Figure 2 Output 3rd rl! J

Claims (1)

[Claims] An adder is provided at the input section of a circuit that reproduces a carrier wave from an audio multiplexed signal, a pilot signal or an audio multiplexed signal containing a pilot signal is added to one input of the adder, and the first horizontal period is added to the other input of the adder. Adjustment means is provided for canceling the horizontal period interference signal contained in the pilot signal by adding a second horizontal period signal whose phase is synchronized with the signal and adjusting the phase and amplitude of the second horizontal period signal. Audio multiplex signal processing device.