Raytheon Company

Charles E Chase, Jr

Gary K Montress

Richard W Laton

Jean E Picquendar

Arthur Yarranton

A microwave surface acoustic wave resonator stabilized oscillator includes an amplifier having an input terminal and an output terminal and a feedback circuit disposed around said amplifier for providing a closed loop about said amplifier having an integral multiple of 2.pi. radians of phase shift and excess small signal gain at a frequency f.sub.o. The SAW resonator is disposed in the feedback means and is selected to operate in a fundamental mode of operation and provides a resonant circuit having a resonant frequency f.sub.o. The feedback circuit around the amplifier causes the loop to oscillate at a frequency at which the phase shift is an integral multiple of 2.pi. radians and which has excess small signal gain. As the circuit starts to oscillate, the overall gain in the loop is compressed and the loop amplifier is forced to operate in a non-linear region. Operation in non-linear region causes the amplifier to generate harmonics of the fundamental frequency and thus, by providing a circuit which extracts the harmonics of the fundamental frequency, rather than the fundamental frequency itself, the frequency range of the amplifier can be extended. Furthermore, by keeping the fundamental frequency signal in the oscillator loop, the required gain of the loop amplifier may be decreased by up to 3 db and thus can potentially lower the noise floor of the oscillator by comparable figure.

Surface acoustic wave oscillator

A surface acoustic wave (SAW) device provides a phase shift and a first predetermined phase shift variation as a function of temperature. A passive network including a passive, reactive component is thermally and electrically coupled to the SAW device. An electrical characteristic of the component has a predetermined variation as a function of the temperature of the reactive component which provides the network with a second, predetermined phase variation as a function of temperature to compensate for the first predetermined phase variation as a function of temperature provided from the surface acoustic wave device. With this arrangement, the phase shift provided from the surface acoustic wave device is substantially invariant with temperature.

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Needham, MA, United States of America

Charles E Chase, Jr