Frequency synthesiser with phase loop with phase detector

摘要

The phase loop contains a voltage controlled oscillator (VCO), with its output coupled via a frequency converter (FU) and a frequency divider (FT), back to a second input of a phase discriminator (PD). A reference oscillator (RO) is coupled to the first input of the frequency discriminator. The phase discriminator output signal, representing the difference in phase between the input signals, is fed to the VCO input via a filter (TP). The reference oscillator contains a digital P-bit accumulator, adding to itself a control word consisting of P-bits. On attaining a highest summation value it transmits an overrun pulse (s1) and starts a new accumulation step. The overrun pulses directly reach the input of the phase detector. Preferably the frequency divider is also a p-bit accumulator, whose overrun pulses (s2) reach the second input of the phase detector.