JPS58143679A - Monitor television receiver - Google Patents

Abstract

PURPOSE:To reduce the sound carrier frequency disturbance due to the variance of an input video carrier frequency, by applying an AFT voltage to a sound trap circuit which is connected to a carrier wave circuit and has a variable trap frequency. CONSTITUTION:A sound carrier variable trap circuit 3 is connected to an input terminal 1 of the high frequency output of a television game machine or the like through an input circuit 2. The AFT voltage is applied as a control signal to this sound carrier variable trap circuit 3 from an AFT detecting circuit 8. This AFT voltage is changed in accordance with the shift of an input video carrier frequency. Thus, the sound carrier frequency is attenuated in accordance with the variance of the frequency of the input video carrier wave, and the sound carrier frequency disturbance to a video signal is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a monitor television receiver connected to video equipment such as MU4MYA.

In general, the high-frequency output frequency signals of video equipment used for video games are not necessarily accurate or stable, so if you receive them as they are, audio beat interference will occur and you will not be able to obtain a high-quality image. . Therefore, the monitor television receiver iJ11m that receives this requires a receiving device equipped with a television tuner having an AFC circuit.

However, the high-frequency output channel of video equipment is often a single channel (for example, 2 channels or 3 channels in the United States), so it is unreasonable to use a receiving device equipped with a general TV tuner as a monitor TV receiver. It was disadvantageous in terms of cost.

The present invention has been made in view of the above-mentioned points, and its object is to provide a monitor television receiver having a function of automatically reducing audio carrier frequency interference caused by a deviation of the audio carrier frequency from the normal frequency. The goal is to provide products at low prices.

Examples of the present invention will be described in detail below.

FIG. 1 shows a block diagram of a monitor television receiver according to an embodiment of the present invention, and an input terminal 1 to which a high frequency output terminal of a video device such as a television game machine is connected has an input for impedance matching and other purposes. A circuit 2 is connected thereto, and an audio carrier variable trap circuit 3 is connected downstream of the input circuit 2. This audio carrier wave variable trap circuit 3 has a tank circuit in which a coil L is connected to a series circuit of a varactor diode D and a capacitor C1 for high frequency bypass and direct current cut, and a tank circuit is connected to a signal line 3a and ground via a coupling capacitor C2. The control (AFT) voltage is applied to the connection point between the cathode of the varactor diode O and the capacitor C1 via the adjustment resistor R. 4 is a prequalification amplifier, a 5-digit bandpass filter, 6 is a main amplifier, and a part of the output signal of the main amplifier 6 is inputted to the AFT detection circuit 8 via the AFT amplifier circuit 7; The AFT voltage is applied as a wrap frequency control voltage to the varactor diode (DK) via the resistor R of the audio carrier variable trap circuit 3. Reference numeral 9 denotes a detection circuit, from which the output signal is extracted as an Eirin signal through an Eirin amplifier circuit 10 on the one hand, and an audio signal after passing through an audio intermediate frequency amplifier circuit 11, an audio detection circuit 12, and an audio amplifier circuit 13 on the other hand. It has become a trap to be taken out.

As shown in Figure 2, the output AFT voltage of the AFT detection circuit 8 becomes the reference voltage when the input signal frequency (Eirin carrier frequency) is the normal frequency fo, and the input signal frequency deviates to f + Δf1. When KFiV·+Δv1, when f is shifted to Δf2, K becomes V·−ΔV.

This AFT voltage is input to the single audio carrier variable trap circuit 3 as described below.

On the other hand, the overall frequency characteristic of the carrier wave circuit part from the input terminal 1 to the output side of the bandpass filter 5 in FIG. 1 becomes the characteristic shown in FIG. , Δf1, etc. fll, f, respectively.
Shifts to the frequency of at.

Therefore, when the audio carrier frequency becomes fat,
This frequency penetrates into the high range of the video frequency and acts as a disturbance component, but the carrier wave trap circuit 3
Since the trap frequency is set to fat depending on the FT voltage,
The frequency signal components are attenuated and interference with the video signal is reduced. That is, the audio carrier frequency component is
The audio carrier wave variable trap circuit 3 automatically attenuates the audio carrier wave to a level K that does not interfere with the video signal, depending on the fluctuation of the audio carrier wave frequency.

As described above, the monitor television receiver according to the present invention applies an AFT voltage that changes according to the deviation of the input video carrier frequency to an audio carrier variable trap circuit with a variable trap frequency connected to a carrier circuit, and The audio carrier wave signal is attenuated by a carrier wave variable trap circuit, and even if the rounding input video carrier wave frequency fluctuates, it is possible to reduce the audio carrier wave frequency interference to the video signal, and a general TV tuner is also required. It is also possible to realize a cost reduction without the need for this, making it extremely suitable for video game machines and the like.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the main parts of a monitor television receiver according to an embodiment of the present invention, Fig. 2 is a characteristic diagram of AFT voltage, and Fig. 3 is a frequency characteristic diagram of the carrier wave circuit section. May 21, 1981 Patent Order No. 026467 2, Name of the invention Monitor TV receiver 3, Relationship to the case of the person making the amendment Patent applicant Address 1116 Suenaga, Takatsu-ku, Yozaki City, Kanagawa Prefecture
Name (661) General Co., Ltd. 4, Agent 6, Number of inventions increased by amendment 07, Specification subject to amendment 8, Contents of amendment

Claims (1)

[Claims] (1) An AFT voltage that changes according to the deviation of the input Eirin carrier frequency is applied to an audio carrier variable trap circuit with a variable trap frequency connected to a carrier circuit, and the audio carrier signal is attenuated by the audio carrier variable trap circuit. What is claimed is: 1. A monitor television receiver comprising: