Scanning radio receiver and frequency synthesizer therefor

摘要

There is disclosed a scanning radio receiver intended for use on the frequencies assigned to the Public Safety Radio Services and which is also operable for reception in the aircraft band from 118 MHz to 136 MHz. A voltage controlled oscillator is provided which is operable at frequencies up to nearly 175 MHz for producing an output signal for direct mixing with received signals in the low and high VHF bands as well as in the aircraft band and for tripling to provide a first local oscillator signal for UHF operation up to 512 MHz. A divider circuit is provided for direct countdown from the frequency of the voltage controlled oscillator to produce a low frequency signal for comparison with a fixed frequency signal of 5 KHz, or in the case of UHF operation, 4.167 KHz. The countdown circuitry along with the phase detector and divider circuits for producing the reference are all mounted on a single integrated circuit chip. Also, a shift register is provided on the chip for control of the divider circuits in response to data entered serially.