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

A TV receiver and receiver technology, applied to color TV parts, TV system parts, discontinuous tuning with a separate pre-tuning circuit, etc., can solve image quality deterioration, video frequency characteristics are different, etc. question

Inactive Publication Date: 2004-10-27
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] According to Figure 1 to image 3 , an embodiment of the present invention will be described as follows.

[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 this PLL circuit 31 includes an oscillator 32 that oscillates 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 oscillating circuit 33 are frequency-divided by respective frequency dividers 35 and 36, and the frequency-divided 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 superheterodyne receivers such as television receivers, a television receiver equipped with the circuit, and a beat improvement method of the television receiver. Background technique [0002] Figure 5 It is a block diagram showing the electrical configuration of a television receiver 1 corresponding to the NTSC or PAL broadcasting system using the superheterodyne system. Receive RF (high frequency) signal from antenna 2 input, first only take out required signal component at the input tuning circuit 3 that band-pass filter is formed, then after high-frequency amplifying circuit 4 amplifies, in the stage that band-pass filter forms In the inter-tuning circuit 5, unnecessary signal components are removed. The RF signal is sent to the mixing circuit 6, mixed with the LO (Local Oscillator) signal generated by the Local Oscillator circuit 7, subjected to frequency conversion, and converted into ...

Claims

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Application Information

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