Frequency synthesizer for improving a unique DDS characteristic

摘要

A frequency synthesizer that improves a unique DDS characteristic, while maintaining a circuit scale (ROM size) of a direct digital synthesizer (DDS). A first digital signal generator generates a quantized frequency signal, and a second digital signal generator generates a frequency signal having a fine frequency resolution and many spurious signals as compared with the first digital signal generator. A filter performs band rejection on an output of the second digital signal generator, and a mixer mixes an output of the first digital signal generator with an output of the filter.