Direct digital synthesizer driven pll frequency synthesizer with clean-up pll

The invention claims a frequency synthesizer, comprising a characterised comprises: For generating frequency supply of variable frequency signal a digital form; A first a pre-formed the determining loop bandwidth and an frequency supply connecting the first phaselocked loop circuit; And is greater than of the first to determine a pre-formed loop bandwidth second by a pre-formed the loop bandwidth and a first phaselocked loop hookup the second phaselocked loop circuit.