US 3,944,925 AGranted

Phase-locked loop transceiver having automatic frequency offset selectability

AssigneeMotorola, Inc.

InventorJon M. De Laune

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Abstract

This specification discloses a frequency synthesizer or phase-locked loop transceiver operating from a reference oscillator source, F.sub.REF. A single phase-locked loop system for the transceiver includes counter means located in a feedback path connected between a voltage controlled oscillator (VCO) and a digital phase detector. The counter is preset to a predetermined number N for generating a frequency representation ##EQU1## The counter means includes logic and decoding circuitry for automatically modifying the ##EQU2## signal representation by a factor M for generating a feedback signal F.sub.F, where F.sub.F is ##EQU3## The feedback signal representation ##EQU4## is applied to the digital phase detector for generating a transmit or receive signal .sup.F OUT, where .sup.F OUT = .sup.F REF .sup.(N .+-. M).

Claims8

Dependent claims

A phase-locked loop system for generating an output signal F.sub.OUT from any first predetermined frequency varying signal N and any second frequency varying signal M offset from said first predetermined frequency varying signal a predetermined amount in response to a reference signal F.sub.REF comprising:

a. a phase-locked loop means having a feed forward path including a phase detector and a voltage controlled oscillator and a feedback path coupled between a first input terminal means and an output terminal means and being responsive to the signal F.sub.REF for generating the signal F.sub.OUT at said output terminal;
b. said phase-locked means further including counter means coupled between said input and said output terminals in said feedback path;
c. said counter means including means for programming a selective digital representation of N and means for generating the offset digital frequency M and storing a digital frequency representation N .+-. M said counter being responsive to F.sub.OUT and said digital representation N .+-. M for generating F.sub.F, where F.sub.F is ##EQU8##

Dependencies are inferred from the claim text.