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PLL circuit and TV receiver using it, and improvement in beat of TV receiver

A technology for television receivers and receivers, which is applied to parts of color televisions, parts of television systems, televisions, etc., can solve the problems of different video frequency characteristics and deterioration of image quality.

Inactive Publication Date: 2008-03-19
SHARP KK
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

In this way, when the frequency shifted IF is detected, there is a problem that the frequency characteristic of the detected video is different from the original characteristic and the image quality deteriorates.

Method used

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  • PLL circuit and TV receiver using it, and improvement in beat of TV receiver
  • PLL circuit and TV receiver using it, and improvement in beat of TV receiver
  • PLL circuit and TV receiver using it, and improvement in beat of TV receiver

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Embodiment Construction

[0025] An embodiment of the present invention will be described below with reference to FIGS. 1 to 3 .

[0026] FIG. 1 is a block diagram showing the electrical configuration of a PLL circuit 31 according to an embodiment of the present invention. The configuration of the PLL circuit 31 includes an oscillator 32 for generating the oscillation of the LO signal, a reference signal oscillation circuit 33 , a phase comparator 34 , and frequency dividers 35 and 36 . The oscillator 32 is realized by a voltage-controlled oscillator or the like that oscillates at a frequency corresponding to the DC control voltage given by the phase comparator 34 .

[0027] The LO signal component generated by the oscillator 32 and the reference signal component generated by the reference signal oscillation circuit 33 are divided by frequency dividers 35 and 36 respectively, and the divided frequency components are compared with each other in the phase comparator 34 to change the frequency. Feedback ...

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Abstract

A PLL circuit is used for a super-heterodyne television receiver. In the PLL circuit, a reference signal oscillator circuit generates a reference signal, and the reference signal is compared to a LO signal in a phase comparator. The phase comparator includes an oscillating circuit, a series circuit of a correcting capacitor and an oscillator corresponding to a predetermined IF signal frequency, another correcting capacitor, and a switch. The switch is turned ON or OFF only when receiving a particular channel in which interference occurs, so as to shift the frequency of the reference signal by several ten kHz. This reduces beats in a particular channel, and prevents deterioration of picture quality in other channels. That is, interference in a particular channel can be reduced without causing any adverse effects in other channels having a relatively high frequency.

Description

technical field [0001] The present invention relates to a PLL circuit suitable for a superheterodyne receiver such as a television receiver, a television receiver equipped with the circuit, and a method for improving the beat of the television receiver. Background technique [0002] FIG. 5 is a block diagram showing the electrical configuration of the television receiver 1 which adopts the superheterodyne type and corresponds to the broadcasting system of NTSC or PAL. For the received RF (high frequency) signal input from the antenna 2, only the required signal components are taken out in the input tuning circuit 3 composed of the band-pass filter, and then amplified by the high-frequency amplifier circuit 4 in the stage composed of the band-pass filter. In the inter-tuning circuit 5, unwanted signal components are removed. The RF signal is sent to the mixer circuit 6, mixed with the LO (local oscillator) signal generated by the local oscillator circuit 7, and subjected to ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H04B1/10H04N5/21H03J3/20H03J5/24H03L7/18H04B1/26H04N5/12H04N5/44H04N5/50
CPCH04N5/21H03J5/244H04N5/50H04N5/126H03J3/20H03L7/18H04N5/4446
Inventor 板屋刚
Owner SHARP KK