Frequency synthesizer

A frequency synthesizer is an electronic circuit for generating any of a range of frequencies from a single fixed timebase or oscillator. They are found in many modern devices, including radio receivers, televisions, mobile telephones, radiotelephones, walkie-talkies, CB radios, cable television converter boxes satellite receivers, and GPS systems. A frequency synthesizer uses the techniques of frequency multiplication, frequency division, direct digital synthesis, and frequency mixing to generate new frequencies which have the same stability and accuracy as the master oscillator.

Three types of synthesizer can be distinguished. The first and second type are routinely found as stand-alone architecture: direct analog synthesis (also called a mix-filter-divide architecture as found in the 1960s HP 5100A) and the more modern direct digital synthesizer (DDS) (table-look-up). The third type are routinely used as communication system IC building-blocks: indirect digital (PLL) synthesizers including integer-N and fractional-N.

It is in some ways similar to a DDS, but it has architectural differences. One of its big advantages is to allow a much finer resolution than other types of synthesizers with a given reference frequency.

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