CIRCUIT FOR OPTIMIZING NOISE OF RECEIVING UNIT ACCORDING TO REFERENCE FREQUENCY CHANGE

摘要

PURPOSE: A circuit for optimizing the noise of a receiving unit according to a reference frequency change is provided to offer a good-quality receiving unit without an intermediate frequency tuning coil by implementing a reference frequency of 10.625MHz and using it as a secondary local signal in common. CONSTITUTION: A reference frequency of 10.625MHz is oscillated through an oscillator(b). The oscillated frequency is amplified and stabilized through a mixer and charge pumps(A,B). The amplified and stabilized frequency is filtered through the first band pass filter, then amplified through an amplifier. The amplified frequency signal is output as the first intermediate frequency to detect an intermediate frequency signal by the second band pass filter(BPF2). As the first intermediate frequency is mixed with the 10.625MHz reference frequency oscillated through the oscillator(b), the first intermediate frequency is converted into the second intermediate frequency.