Direct broadcasting satellite tuner, e.g. for satellite TV

摘要

The direct broadcasting satellite (DBS) tuner has a negative feedback and image compression circuit. In this, the baseband frequency signal output from the demodulator circuit is amplified by a baseband amplifier circuit and then fed back to a variable capacitance diode through a phase correction circuit. This allows the variable capacitance diode to be controlled by a 12V power supply. The fed-back signal is further input to a voltage controlled oscillator in the microwave monolithic inaugurated circuit for mixing with the radio frequency signal, allowing a modulated image intermediate frequency signal to be compressed. The compressed image intermediate frequency signal effectively eliminates noise, increases sound/noise ratio and improves the threshold.