US 4,712,078 AGranted

Dielectric resonator oscillators with digital temperature compensation

AssigneeThe United States of America as represented by the Secretary of the Air Force

InventorsAndrew J. Slobodnik, Jr., Martin R. Stiglitz, George A. Roberts, Richard T. Webster

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Abstract

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).

Claims13

Dependent claims

In combination with a dielectric resonator oscillator including a dielectric resonator which oscillates to produce a radio frequency (RF) clock signal which has phase shift characteristics corresponding to a resonant frequency, said resonant frequency having a frequency drift with changes in ambient temperature, said dielectric resonator oscillator including microstrip lines which are electrically connected in series with a directional coupler, said microstrip lines being placed in proximity to said dielectric resonator which couples said radio frequency clock signal between said microstrip lines thus closing the oscillator loop, a temperature compensation feedback circuit which reduces temperature sensitivity and frequency drift in said clock signal, said temperature compensation feedback circuit comprising:

a temperature sensing means which produces an output signal which indicates the ambient temperature, said output signal being a temperature reading;
a correlation menas which is electrically connected in series with said temperature sensing means, and which receives said temperature reading from said temperature sensing means, and produces an output signal which indicates an amount of phase adjustment which is necessary in said clock signal to eliminate frequency drift due to changes in the ambient temperature;
a digital-to-analog converter which is electrically connected in series with said correlation means, and which receives said output signal from said correlation means, and converts it into an analog siganl;
a phase shifter which is electrically connected in series with said digital-to-analog converter, and which receives said clock signal and said analog signal from said digital-to-analog converter, said phase shifter also being electrically connected with said microstrip lines, and outputting an adjusted clock signal which compensates for the phase shift in the dielectric resonator due to changes in the ambient temperature;
and
an ampliifer which is electrically connected in series between said phase shifter and said directional coupler, and which produces an output by receiving and amplifying said adjusted clock signal from said phase shifter.

3 more elements

A temperature compensation feedback circuit, as defined in lailm 2, wherein said calibration means comprises:

a variable temperature oven encompassing and heating to different ambient temperatures said dielectric resonator and microstrip lines, said ambient temperature being monitored by said temperature sensing means which indicates the ambient temperature around the dielectric resonator and microstrip lines;
a frequency counter which connects with said directional coupler, and, which produces an output signal which indicates the frequency of said clock signal as it passes through the directional coupler;
and
a control computer which is electrically connected with said temperature sensing means, and which receives said output signal from said temperature sensing means and said frequency signal from said frequency counter, said control computer producing a correction signal by comparing said frequency with the desired frequency, said control computer sending said temperature reading and said correction signal to printing means after producing it, said control computer sending control signals to said variable temperature oven to direct the heating to different ambient temperature by the variable oven.

1 more element

In combination with a dielectric resonator oscillator, including a dielectric resonator which oscillates to produce a radio frequency (RF) clock signal which has phase shift characteristics corresponding to a resonant frequency, said resonant frequency having a frequency drift with changes in ambient temperature, said dielectric resonator oscillator including microstrip lines which are eletrically connected in series with a directional coupler, said microstrip lines being placed in proximity to said dielectric resonator which couples said radio frequency (RF) clock signal between said microstrip lines thus closing the oscillator loop, a temperature compensation feedback process which reduces temperature sensitivity and frequency drift in the clock signal in said microstrip, said process comprising the steps of:

sensing the ambient temperature around the dielectric resonator;
using the ambient temperature to determine a phase shift to be applied to the clock signal which will compensate for frequency drift due to changes in the ambient temperature;
and
setting the phase shift in the oscillator loop to compensate for the frequency drift due to changes in ambient temperature.

1 more element

Dependencies are inferred from the claim text.