United States of America As Represented by the Secretary of the Air Force

Andrew J Slobodnik, Jr

Kenneth R Laker

Richard T Webster

Martin R Stiglitz

Thomas L Szabo

Roger D Colvin

George A Roberts

A digital compensation circuit for improving the temperature stability of dielectric resonator oscillators is disclosed. A temperature sensor indicates a measure of ambient temperature which is correlated with an amount of phase shift necessary to compensate for frequency drift in a dielectric resonator oscillator. The correlation is made using a correction table or correction function which is determined empirically in a calibration process. The necessary phase shift is then supplied via a voltage controlled phase shifter. This phase shifter is part of the RF oscillation loop which also includes an amplifier, directional coupler and dielectric resonator filter (including microstrip).

Dielectric resonator oscillators with digital temperature compensation

The inherent temperature instability of surface acoustic wave (SAW) clock oscillators is improved by the use of a thermometer oscillator circuit that senses temperature changes in the SAW substrate. The thermometer oscillator is used in combination with a calibrated programmable read only memory and a logic circuit and provides frequency corrections to the clock oscillator. The basic device is an oscillator clock circuit using a SAW substrate having a delay path orientation with good temperature stability. A second oscillator, the thermometer oscillator circuit, and the electronic compensation scheme are added in order to produce minimum temperature coefficient of delay over all temperatures in the range of interest. The thermometer oscillator delay path utilizes a high temperature coefficient of delay orientation of the same SAW substrate and at an appropriate angle to the clock oscillator delay path orientation. Its frequency of oscillation is used as a highly accurate thermometer in order to control a correction signal applied to a variable phase shifter in the clock oscillator loop.

Saw oscillator with digital compensation for temperature related

Passband distortion due to mass loading in withdrawal weighted surface acoustic wave transducers is substantially reduced by a thinning technique in which interdigital transducer electrodes are selectively withdrawn to synthesize a response function H.sub.o '(N). H.sub.o '(N) is a modified response function that has been scaled from a desired response function H.sub.o (N) by a thinning factor THIN. THIN is a positive, non-zero constant with a maximum value of unity. Thinned withdrawal weighted transducers fabricated in accordance with the technique have electrode weights that are normalized to less than unity and achieve mass loading reduction with a minimum amount of degradation of the desired response function.

Thinned withdrawal weighted surface acoustic wave interdigital

A surface acoustic wave bandpass filter having a flat frequency response in the passband and an exponentially decaying out-of-band response is realized by designing its transducer electrodes to have an appropriate number of discretely apodized interdigital fingers. The apodization or overlap coefficients H.sub.o (N) of adjacent fingers are determined from an analytically derived expression that incorporates factors for the filter time length parameter, the filter center frequency, bandwidth, transition bandwidth falloff, and a ripple reduction parameter.

Surface acoustic wave filter

The particular anisotropy of a specific propagation surface orientation on a single crystal lithium tantalate substrate member is utilized to achieve low diffraction, low spurious response surface acoustic wave (SAW) propagation. The preferred embodiment utilizes a propagation surface that substantially coincides with a plane defined by the Euler angles Lambda = 0.degree., Gamma = 166.65 (+0, -0.3).degree., and Theta = 90.degree..

Growing community of inventors

Malden, MA, United States of America

Andrew J Slobodnik, Jr