PHASE LOCKED LOOP WITH CONTROLLABLE RESPONSE TIME

摘要

PROBLEM TO BE SOLVED: To obtain a phase locked loop whose response time is controlled selectively by arranging a phase detector and an amplifier for a feedback integration device in an integrated circuit. SOLUTION: A frequency of a local oscillator 911 is controlled by a PLL 919 consisting of a phase locked loop(PLL) integrated circuit(IC) 921, an external frequency reference crystal oscillator 923, and an external filter circuit network 925. The frequency of the local oscillator 911 is controlled by the PLL 919 according to data generated by a microprocessor 19. The filter circuit network 925 included in the PLL 919 incorporates a loop filter applying filtering processing to a phase error signal to generate a tuning control voltage for the local oscillator 911 from the phase error signal. The tuning control voltage is used to control an adjustable band pass filter and fed to the local oscillator 911. Furthermore, the tuning control voltage varies proportional to a frequency locked to the phase of the reference frequency by the PLL integrated circuit 923 to control the PLL response time.