Abstract Electrical circuits which are sensitive to frequency drift with temperature changes are stabilized by employing a matched pair of surface wave devices; the first having a negative temperature coefficient Alpha 1; the second having a positive temperature coefficient Alpha 2. An oscillator circuit is temperature compensated by inserting a matching pair of surface wave delay elements in the feedback loop and choosing the delay time so that Alpha 1t1 - Alpha 2t2, where t1, t2 are the delay times provided by the delay elements having temperature coefficients Alpha 1, Alpha 2. A first oscillator circuit comprises a single amplifier and a pair of matched surface wave delay elements coupled in tandem in the feedback loop. A second oscillator circuit comprises a pair of amplifiers and a pair of matched surface wave delay elements alternately coupled in a closed loop configuration so that the delay elements are interlaced with the amplifiers. In a receiver system having a mixer, a local oscillator, and an IF filter for converting RF input signals to IF output signals, temperature compensation is achieved by employing a surface wave delay element in the local oscillator feedback loop and a surface wave integratable filter as the IF filter and choosing the temperature coefficients and local and intermediate frequencies so that Alpha LOfLO - Alpha IFfIF, in systems where fLO<fRF and Alpha LOfLO Alpha IFfIF when fLO>fRF, where Alpha LO'' Alpha IF are the temperature coefficients of the delay element and filter, respectively, and fRF, fIF and fLO are the RF intermediate and local oscillator frequencies, respectively. The oscillator circuits are voltage tuned by providing an intermediate electrode on the active surface of a surface wave delay element and impressing a DC signal or an AC signal or a combination of both between the intermediate electrode and the ground plane of the delay element.
A temperature compensated receiver, said receiver comprising: input means for receiving RF signals having a frequency fRF; a mixer having a first input coupled to said input means, and a second input, a surface wave integratable filter having a temperature coefficient Alpha IF, said filter having an input coupled to said mixer and an output for furnishing intermediate frequency signals to an output terminal; and a local oscillator coupled to said second input of said mixer, said local oscillator comprising an amplifier and a surface acoustic wave delay line coupled in a closed loop configuration, said surface acoustic wave delay line having a temperature coefficient Alpha LO, said temperature coefficients being selected to satisfy the relation Alpha LOfLO Alpha IFf IF, where FLO f1F are the local oscillator and intermediate frequencies, respectively, when f LO>f FR: said temperature coefficients being selected to satisfy the relation Alpha LOfLO Alpha IFfIF when LOf<fRF.
Claim 2
Dependent Claim
151 words
A temperature compensated receiver, said receiver comprising: input means for receiving RF signals having a frequency fRF; a mixer having a first input coupled to said input means, and a second input, a surface wave integratable filter having a temperature coefficient Alpha IF, said filter having an input coupled to said mixer and an output for furnishing intermediate frequency signals to an output terminal; and a local oscillator coupled to said second input of said mixer, said local oscillator comprising an amplifier and a surface acoustic wave delay line coupled in a closed loop configuration, said surface acoustic wave delay line having a temperature coefficient Alpha LO, said temperature coefficients being selected to satisfy the relation Alpha LOfLO Alpha IFf IF, where FLO f1F are the local oscillator and intermediate frequencies, respectively, when f LO>f FR: said temperature coefficients being selected to satisfy the relation Alpha LOfLO Alpha IFfIF when LOf<fRF.
Claim 3
Dependent Claim
60 words
The receiver of claim 1 wherein said surface acoustic wave delay line includes an input transducer, an output transducer, and a control electrode intermediate said input and said output transducers; and further including means coupled to said control electrode for enabling voltage tuning of the delay time provided by said delay line to control the frequency of said local oscillator.
Claim 4
Dependent Claim
22 words
The receiver of claim 2 wherein said surface wave integratable filter is fabricated from a piezoelectric material having a relatively high-coupling coefficient.
Claim 5
Dependent Claim
43 words
The apparatus of claim 3, wherein said surface wave integratable filter is fabricated from a first piezoelectric material having a positive temperature coefficient and wherein said surface acoustic wave delay line is fabricated from a second piezoelectric material having a negative temperature coefficient.
Claim 6
Dependent Claim
22 words
The apparatus of claim 4 wherein said first and second piezoelectric materials comprise YZ cUt lithium niobate and XY cut quartz, respectively.