Patent ID: 7170357
Filing Date: 2007-01-30
Classification: H03B

Abstract:
1. A crystal oscillator having an oscillatory signal loop feedback path, comprising: a crystal filter having a plurality of crystals resonant at a nominal RF operating frequency, wherein each said crystal of said plurality of crystals is joined with an adjacent crystal of said plurality of crystals; and which includes a plurality of inductors, each in parallel with a respective one of said crystals to neutralize the effects of static capacitance associated with each said crystal; and a reactive coupling element coupled between each pair of adjacent crystals of said plurality of crystals; a voltage controlled phase shifter having an input, an output and a control input and operable to phase shift the signal in said feedback loop in response to a voltage applied to said control input; an amplifier for amplifying the output of said voltage controlled phase shifter; a power divider having first and second outputs, said first output constituting the RF output of said crystal oscillator, said second output being coupled to said crystal filter; a loop phase shift circuit connected in said feedback loop for ensuring that the total feedback loop phase shift at the operating frequency of said oscillator is a multiple of 360°; and a band pass mode selection circuit in said feedback loop for attenuating signals occurring at unwanted crystal resonant responses, while passing the signal at said operating frequency.