JPH03211919A - Television receiver - Google Patents

Abstract

PURPOSE:To obtain a flat base band characteristic over the range from the low area to high frequencies to obtain a television receiver having high picture quality by inserting a parallel circuit composed of a variable inductor and a capacitor in a signal path between the output terminal of the intermediate frequency signal of a tuner and a Nyquist filter. CONSTITUTION:Between the output terminal of a tuner 102 and a Nyquist filter 108, a controller 107 is provided to control the signal pass characteristic, and a resonance point between a parallel variable inductor 106 and a capacitor 105 inserted and connected in series to an IF signal output terminal 103 of the tuner 102 and the Nyquist filter 108 is selected near the upper adjacent band of a video carrier frequency converted to the intermediate frequency. Thus, the pass characteristic especially near the video frequency of the Nyquist filter can be controlled and the signal pass characteristic to the Nyquist filter 108 can be controlled by a simple means. Thus, the television receiver with especially high picture quality can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a television receiver, and more particularly to a television receiver that can obtain high-quality images by improving signal passing characteristics.

[Conventional technology]

Conventionally, in order to obtain the desired signal passing characteristics to improve image quality,
In the tuner's internal circuit, if transistors with standard DC current amplification factors are used for the buffer amplifier transistors, and transistors with large and small DC current amplification factors are used for the post amplifier transistors, a simple circuit can be created. An intermediate frequency amplification circuit has been proposed which stabilizes the output waveform characteristics by correcting variations in the input capacitance of transistors depending on the configuration (see Japanese Utility Model Publication No. 61-28405).

Also, as a video intermediate frequency amplification circuit, the vicinity of the chroma signal of the video intermediate frequency signal and the vicinity of the audio intermediate frequency signal are extracted from the intermediate frequency signal that has passed through the front end, and the vicinity of the chroma signal is in phase, and the vicinity of the audio intermediate frequency signal is in phase. A video intermediate frequency amplification circuit including a band correction circuit that amplifies each phase has been proposed (see Japanese Utility Model Application Publication No. 163494/1983).

[Problem to be solved by the invention]

In the above-mentioned conventional techniques, the former method may be inappropriate because it exhibits a gradual change in pass characteristics, and the latter method requires a considerably large-scale circuit and is expensive to implement.

SUMMARY OF THE INVENTION An object of the present invention is to provide a television receiver that can adjust the signal passing characteristics up to the Nyquist filter by simple means and has particularly high image quality.

[Means to solve the problem]

In order to achieve the above object, an adjustment mechanism for controlling signal passing characteristics is provided between the tuner output terminal and the Nyquist filter.

[Function] By selecting the resonance point of the parallel variable inductor and capacitance inserted and connected in series to the IF signal output terminal of the tuner and the Nyquist filter near the upper adjacent band of the video carrier frequency converted to IF, the Nyquist filter It is possible to control the pass characteristics near the video frequency and obtain the desired pass characteristics.

〔Example〕

The present invention will be explained below using examples.

FIG. 1 is a block diagram showing one embodiment of the present invention.

101 is a TV signal input terminal, 102 is a tuner, 1
03 is an iF signal output terminal frequency-converted within the tuner, 104 is an impedance or signal level conversion circuit, 105 is a tuning capacitor, 106 is a variable inductor, 107
is a damping resistor, 108 is a Nyquist filter, 10
9 is an IF signal amplification and video detection circuit, 110 is an audio detection circuit, and 112 is a video output terminal.

113 is an audio output terminal, and 111 is a tuner selection control circuit.

Portions other than the main parts related to the present invention are shown in block diagrams. Further, 104 is a block diagram of an impedance conversion or signal level conversion circuit using MOSFETs, bipolar transistors, or the like.

A television signal is input from 101, and a desired channel is selected internally by a channel selection control circuit 111. At this time, the signal of the desired channel is converted to an intermediate frequency (IF) and output to the tuner output terminal 103. This signal is band limited by 108 Nyquist filters. Thereafter, it is converted to baseband by IF amplification and video detection at 109 and output from a terminal at 112. In order to improve the picture quality of the television, it can be achieved by uniformly extending the above-mentioned baseband signal band characteristics to a high frequency range. In the figure, a tuning capacitor 105 and a variable inductor 106 are tuned in parallel near the upper side of the IF video carrier frequency. This makes it possible to change the signal passing characteristics particularly in the vicinity of the IF video frequency, and the damping resistor 107 is used to correct the amount of change described above. 104
indicates an impedance conversion or signal level correction circuit composed of resistors, capacitors, bipolar transistors, etc.

〔Effect of the invention〕

According to the present invention, since the pass characteristics can be adjusted with an inexpensive circuit configuration, the characteristics from the low range to the high range of the baseband can be flattened, so that a high-quality television receiver can be provided.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention. 105... Tuning capacity, 106... variable inductor, 107...damping resistance.

Claims (1)

[Claims] 1. A tuner that receives a television signal, converts it to an intermediate frequency (IF) band, and outputs it; and a tuner that receives the signal converted to the intermediate frequency (IF) band, further limits the band, and outputs it. A television receiver comprising a Nyquist filter, a parallel circuit comprising a variable inductor and a capacitor connected in parallel to each other in a signal path between the intermediate frequency signal output terminal of the tuner and the Nyquist filter. A television receiver characterized in that the resonance point of the variable inductor and capacitor is tuned to a frequency near an upper adjacent band of a video carrier wave converted to an intermediate frequency to change signal passing characteristics. 2. The television receiver according to claim 1, further comprising a resistor connected in parallel to the parallel circuit to correct the amount of change in the signal passing characteristic.