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Damping decoupled oscillator using a high impedance crystal

  • US 4,810,922 A
  • Filed: 01/19/1988
  • Issued: 03/07/1989
  • Est. Priority Date: 01/19/1988
  • Status: Expired due to Fees
First Claim
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1. A damping decoupled crystal oscillator comprising:

  • (a) a piezoelectric crystal driven to oscillate close to its resonant frequency, producing a periodic signal, the piezoelectric crystal being connected to a feedback loop providing a feedback signal derived from the periodic signal, to sustain oscillation of the piezoelectric crystal;

    (b) a variable gain amplifier connected to amplify the periodic signal produced by the piezoelectric crystal at a gain dependent upon a gain control signal;

    (c) variable phase shift means, connected in series relationship with the variable gain amplifier, for introducing a phase shift in the signal produced by the piezoelectric crystal in response to a phase control signal, the series connected variable gain amplifier and phase shift means producing an output signal comprising the feedback signal;

    (d) level detecting means connected to receive the output signal and operative to determine the amplitude of the output signal to produce the gain control signal;

    (e) damping change compensation means, connected to receive the gain control signal, for producing the phase control signal as a function of the gain control signal, the frequency of said output signal being thus compensated for and decoupled from changes in damping to which the piezoelectric crystal may be subjected.

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