Phase lock loop frequency synthesis controller includes digital modulator

摘要

A digital modulator particularly suitable for use in the controller for the fractional division divider in a phase lock loop of a digital frequency synthesizer includes an adder 61 receiving a control signal X and a feedback signal e and producing a multibit output that is the addition of the inputs. Output selection logic 62 receives an input derived from at least one bit of the adder output and produces a modulator output Y. A feedback path includes a latch 65 that receives a group of the bits output by the adder to produce the feedback signal.