| US 7,545,224 B2 | ||
| Cost effective low noise single loop synthesizer | ||
| Colin Ka Ho Chow, Brighton, Mass. (US); and David E. O'Brien, Boston, Mass. (US) | ||
| Assigned to Teradyne, Inc., North Reading, Mass. (US) | ||
| Filed on Apr. 12, 2007, as Appl. No. 11/734,637. | ||
| Prior Publication US 2008/0252384 A1, Oct. 16, 2008 | ||
| Int. Cl. H03L 7/08 (2006.01) | ||
| U.S. Cl. 331—22 [331/16; 331/18; 331/41] | 25 Claims |
| 1. 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.
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