Patent ID: 7545224

Claim:
A microwave synthesizer, comprising: a reference oscillator for generating a reference frequency; a DDS modulation circuit for generating a modulated DDS signal; and a phase-locked loop circuit, coupled to the reference oscillator and the DDS modulation circuit, for generating a variable frequency output signal, wherein the phase-locked loon circuit includes— a phase comparison circuit having a first input coupled to the reference oscillator, a second input for receiving a feedback signal, and an output, a controllable oscillator having a control input coupled to the output of the phase comparison circuit and an output for generating the variable frequency output signal, and a first mixer circuit having a first input coupled to the DDS modulation circuit, a second input coupled to the output of the controllable oscillator, and an output coupled to the second input of the phase comparison circuit, and wherein the DDS modulation circuit includes a local oscillator circuit, a DDS circuit, having a clock input coupled to the local oscillator circuit and an output for providing an output signal of programmable frequency, and a second mixer circuit having a first input coupled to the output of the DDS circuit, a local oscillator input coupled to the local oscillator circuit, and an output for generating the modulated DDS signal.