A 3 to 30 MHz high-resolution synthesizer consisting of a DDS, divide-and-mix modules, and a M/N synthesizer

A 3 to 30 MHz synthesizer is described that uses divide and mix modules to clean up the output of a DDS resulting in a building block signal source that generates an output at 10.7 MHz with a 4.2% tuning range. The divide and mix modules are based on a previously described narrowband design that has been modified for greater tuning range. Both the old and new designs exploit inexpensive ceramic filters that are normally used in the IF stages of radio receivers. The basic 10.7 MHz band is applied to an M/N synthesizer to produce an output band from 3 to 30 MHz. Various techniques for filtering harmonics from the frequency divider output are discussed, as well as circuit design details of the 10.7 MHz mixers and filters. A PLL version of the M/N synthesizer is described that covers the band from 240 to 700 MHz, again starting from the 10.7 MHz input.