Patent ID: 7002423
Filing Date: 2006-02-21
Classification: H03B

Abstract:
1. An oscillator comprising: an oscillating crystal having a fundamental frequency of oscillation but forced to oscillate at a third overtone of the fundamental frequency, the third overtone being a frequency of about three times the fundamental frequency; the oscillating crystal coupled between a first input node and a second input node; a first amplifier circuit having an input attached to the first input node and generating a first output, the first amplifier also having a first phase-shift node; a second amplifier circuit having an input attached to the second input node and generating a second output, the second amplifier also having a second phase-shift node; a tuning resistor coupled between the first input node of the first amplifier and the second input node of the second amplifier, the tuning resistor having a value such that an absolute value of a product (gm×Xc a multiplier, coupled to the first amplifier circuit and to the second amplifier circuit, for generating a doubled output from the first output and from the second output, the doubled output having an output frequency that is double the third overtone and about six times the fundamental frequency of the oscillating crystal; and an output filter, attached to the doubled output, for attenuating signals having a frequency of the third overtone, but for passing signals having the output frequency, whereby the oscillating crystal is forced to oscillate at the third overtone, while the doubled output is six times the fundamental frequency of the oscillating crystal.