COMPENSATING TEMPERATURE NULL CHARACTERISTICS OF SELF-COMPENSATED OSCILLATORS

الوصف

Techniques are described that enable controlling the TNULL characteristic by controlling the magnitude and direction of the frequency deviation versus temperature, and thus, compensating the frequency deviation. It is worth noting that compensating an SCO operating at TNULL is more convenient than compensating a conventional LC oscillator operating at a phase away from ΦGNULL, for example as in U.S. Pat. No. 7,332,975 and U.S. Pat. No. 8,134,414. This stems from the fact that the magnitude of the frequency deviation of the SCO is much smaller than that of the conventional LC oscillators. Thus, the SCO offers a better initial point to apply frequency compensation which yields the following advantages in the compensation system: 1. Operating at TNULL requires a smaller dynamic range for the compensation circuits because the frequency excursions that should be compensated in the case of the SCO are appreciably smaller than those in the case of the conventional LC oscillator. 2. Lower frequency deviation at TNULL implies that a lower temperature-to-frequency gain is required at the compensation loop, resulting into lower noise translation from the temperature sensor and the compensation circuitry to the oscillator output phase noise. 3. The oscillator may become less sensitive to process corners when trimmed to operate at TNULL.

النواحي

1. An oscillator circuit comprising - an oscillator comprising: - one or more frequency determining tank circuit; -one or more amplifiers coupled to the one or more tank circuits; circuitry for causing a phase shift between voltage and current of the one or more tank circuits, for causing the oscillator to operate at a temperature null operating point of reduced frequency variation over a temperature null temperature range; one or more output buffers coupled to the oscillator; and a temperature compensation circuit comprising a temperature sensor and a control circuit coupled to the temperature sensor for generating one or more compensation signals, the one or more compensation signals being applied to the oscillator for reducing temperature variations over frequency at least within the temperature null temperature range. 2. The oscillator circuit of claim 1, wherein the one or more compensation signals are applied to the circuitry for causing a phase shift; thus controlling the phase shift of the one or more tank circuits to follow a desired function across temperature. 3. The oscillator circuit of claim 1, wherein the one or more compensation signals are applied to the one or more tank circuits; thus controlling the impedance of the one or more tank circuits to follow a desired function across temperature. 4. The oscillator circuit of claim 1, wherein the one or more compensation signals are applied to the one or more output buffers; thus controlling the input impedance of the one or more output buffers to follow a desired function across temperature. 5. The oscillator circuit of claim 1, wherein the one or more compensation signals are applied to the one or more tank circuits and the one or more output buffers.? Should we claim all the combinations? Or is it there implicitly? 6. The oscillator circuit of claim 1, wherein the control circuit comprises one or more profile generators for generating one or more temperature-dependent signals. 7. The oscillator circuit of claim 1, wherein the one or more compensation signals are analog. 8. The oscillator circuit of claim 1, wherein the one or more compensation signals are digital. 9. The oscillator circuit of claim 1, wherein the compensation signals are a mix of analog and digital signals 9. The oscillator circuit of claim 1, wherein the oscillator is an I/Q oscillator comprising an I oscillator core and a Q oscillator core, and two coupling transconductance cells coupling the I oscillator core and the Q oscillator core, transconductances of the coupling transconductance cells being chosen to cause the oscillator to operate at the temperature null operating point. 10. The oscillator circuit of claim 9, wherein the one or more compensation signals are used to vary the coupling transconductances as a function of temperature. 11. A method of producing a temperature-compensated oscillator signal?, comprising: operating an oscillator at a temperature null operating point of reduced frequency variation over a temperature null temperature range; sensing temperature; generating one or more temperature-dependent compensation signals; and applying the one or more compensation signals to the oscillator for reducing temperature variations over frequency at least within the temperature null temperature range. 12. The method of claim 11, comprising: using one or more tank circuits to determine an oscillator frequency; and using the one or more compensation signals to influence a phase shift between voltage and current of the one or more tank circuits. 13. The method of claim 12, comprising applying the one or more compensation signals to the one or more tank circuits. 14. The method of claim 12, comprising using one or more output buffers to produce one or more output signals, and applying the one or more compensation signals to the one or more output buffers. 15. The method of claim 14, comprising applying the one or more compensation signals to the one or more tank circuits and the one or more output buffers. 16. The method of claim 11, comprising using one or more profile generators for generating one or more temperature-dependent compensation signals. 17. The method of claim 16, wherein the one or more compensation signals are analog. 18. The method of claim 16, wherein the one or more compensation signals are digital. 19. The method of claim 16, wherein the compensation signals are a mix of analog and digital signals.

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