A 640MHz low phase noise reference source

A 640 MHz low phase noise reference source is developed based on a 2/spl times/2 frequency doubler driven by a very low phase noise 160 MHz crystal oscillator. The phase noise at 100 kHz offset frequency from the 640 MHz reference source measured by an HP3047A is /sup /spl I.bar//160 dBc/Hz, and the spuriousness is lower than /sup /spl I.bar//100 dBc within a 40 MHz offset frequency range.