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Low power transmitter frequency stabilization

  • US 4,794,622 A
  • Filed: 05/19/1988
  • Issued: 12/27/1988
  • Est. Priority Date: 06/03/1985
  • Status: Expired due to Fees
First Claim
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1. A miniature hand-held transmitter comprising:

  • a housing;

    a fixed-frequency transmitter circuit mounted within said housing;

    battery means within said housing for powering said transmitter circuit; and

    switch means connecting said battery means to said transmitter circuit;

    said transmitter circuit having a tuned circuit, a transistor, and a surface acoustic wave resonator, said tuned circuit including an inductor connected to the collector of said transistor and in series with said battery means, said switch means and a first resistor, a first capacitor connected between the collector and the emitter of said transistor, a second capacitor connected between the emitter of said transistor and ground, and a third capacitor connected to said inductor and said first resistor and also connected to ground;

    a second resistor connected between the emitter of said transistor and ground;

    said surface acoustic wave resonator being connected to the base of said transistor and to ground; and

    an encoding circuit operatively coupled to said transmitter circuit;

    said transmitter circuit having a resonant frequency within a prescribed number of cycles of the frequency of resonance of said surface acoustic wave resonator, whereby the frequency of operation of said transmitter is controlled by said surface acoustic wave resonator to be within a predetermined tolerance for each of the conditions of the transmitter operating in the housing in free space or when clasped by a hand of a user when operating said switch and wherein said inductor provides the antenna of said transmitter circuit so that the antenna is disposed completely within said housing.

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