Low power transmitter frequency stabilization

摘要

An improved miniature hand-held low power transmitter utilizing a surface acoustic wave (SAW) resonator as the control element to establish the carrier frequency of the oscillator. The SAW resonator stabilizes the frequency of the transmitter to within 0.05% of the center frequency of the SAW resonator for the condition of the user's hand enclosing the transmitter. This stability allows the companion receiver to operate at a narrow bandwidth, 0.1% of the center frequency of the SAW resonator, thus reducing the spurious noise received by the receiver. The configuration of the transmitter allows schemes such as pulse position or pulse width modulation to be utilized to encode the transmitted information. The physical size of the SAW resonator allows the transmitter to be mounted within a housing small enough to be enclosed by the user's hand.