KR970013686A - Tuner device for satellite broadcasting - Google Patents

Abstract

The present invention relates to a tuner device for satellite broadcasting, and an object of the present invention is to provide a tuner device for satellite broadcasting that can accurately control an intermediate frequency input to the demodulator and can stably demodulate the signal. In order to achieve the above object, a satellite broadcasting tuner device according to the present invention is configured to mix a signal received by an antenna and converted into a first intermediate frequency of 1 GHz band with an oscillation frequency of a second local oscillator to convert to a second intermediate frequency. A first mixer, a second mixer for mixing the second intermediate frequency with the oscillation frequency of the second local oscillator and converting it into a third intermediate frequency, and a baseband for mixing the third intermediate frequency with the oscillation frequency of the crystal voltage controlled oscillator A third mixer and a third mixer for converting the signal into the signal of the third mixer and the third intermediate frequency of the baseband filtered by the low pass filter and the oscillation frequency of the crystal voltage controlled oscillator A frequency error detector for supplying the wide loop filter and the narrow bandwidth loop filter, and a voltage inputted through the wide bandwidth loop filter. And the voltage V _H, the level comparator for supplying a two-level decision signal to the microcomputer by comparing the V _L corresponding to the defined frequency difference, so that the first intermediate frequency error smaller as the output signal of the level comparator in accordance with the channel selection signal A microcomputer for changing the set digital data and supplying the phase synchronizing loop, a phase synchronizing loop for controlling the oscillation frequency of the first local oscillator by comparing the oscillation frequency of the first local oscillator with the digital data applied from the microcomputer; The switching circuit is configured to switch according to the output state of the Lebec comparator so as to add a voltage input through the loop filter having a narrow bandwidth to the second local oscillator to correct the error of the third intermediate frequency.

Description

Tuner device for satellite broadcasting

Since this is an open matter, no full text was included.

3 is a detailed circuit diagram of a tuner device according to the present invention.

4 is a circuit diagram of the level comparator shown in FIG.

5 is a graph showing the relationship between the input and output of the level comparator shown in FIG.

Claims (3)

A first mixer for converting a signal received at an antenna into a first intermediate frequency of 1 GHz and then inputting a tuner input terminal to an oscillation frequency of a second local oscillator and converting the signal into a second intermediate frequency; and the second intermediate frequency And a third mixer for mixing the oscillation frequency of the second local oscillator and converting it into a third intermediate frequency, and a third mixer for mixing the third intermediate frequency with the oscillation frequency of the crystal voltage controlled oscillator and converting the signal into a baseband signal. The output of the third mixer detects the difference between the third intermediate frequency of the baseband filtered through the low pass filter and the oscillation frequency of the crystal voltage controlled oscillator. and a frequency error detector to be supplied to the filter, the voltage V _H, V _L, which is the bandwidth corresponding to the voltage and a predetermined frequency difference inputted through the wide loop filter A level comparator for supplying two level determination signals to the microcomputer and a digital data set according to the channel tuning signal so as to reduce the first intermediate frequency error according to the output signal of the level comparator. And a phase-locked loop for controlling the oscillation frequency of the first local oscillator by comparing the oscillation frequency of the first local oscillator with the digital data applied from the microcomputer and a loop having a narrow bandwidth by switching according to the output state of the level comparator. And a switching circuit configured to add a voltage input through the filter to the second local oscillator to correct an error of the third intermediate frequency. The oscillator of claim 1, wherein the crystal voltage controlled oscillator stabilizes demodulation by controlling its oscillation frequency by outputting a frequency error detector through a loop filter when an error of a third intermediate frequency _falls within f ₀ ± Δf _VCKO . Satellite tuner device, characterized in that. The method of claim 2, wherein the level comparator is the input voltage is greater than V _H, the High signal is output, and a first comparator which has a low signal output is smaller than the V _H, when the input voltage is greater than V _L, the And a second comparator for outputting a low signal when the high signal is output and smaller than V _L. ※ Note: The disclosure is based on the initial application.