Digitally-corrected temperature-compensated crystal oscillator having a correction-suspend control for communications service

Abstract

A radio transceiver having digitally-corrected temperature-compensated crystal oscillators (DTCXOs) including digital frequency temperature compensation circuits that are temporarily suspended from being updated, such that temperature compensation updates that can generate noise during periods of reception and transmission that could interfere with the audio channel and/or signal synchronization will be postponed. Temperature is converted to a digital signal that is then used to address a PROM. The PROM outputs a correction word appropriate for the temperature reading and inputs this to a latch. A timing control loads the latch after data has settled. The latched correction word is connected to a bank of switches and capacitors that trim the frequency of the crystal oscillator. During radio transmission and/or reception, the latch will be suspended from loading any new correction words. The last valid correction word, however, will remain.

What is claimed is: .[. 
     
       1.  A temperature-compensated oscillator, comprising: means to generate a frequency having an output;   means to adjust said frequency coupled to said frequency generator means;   temperature measurement means, coupled to said frequency adjustment means, in thermal proximity to the frequency generator means;   means to periodically update the frequency adjustment means, coupled to said frequency adjustment means, in response to the temperature measurement means;   means to suspend the periodic update of the frequency adjustment, coupled to said update means, in response to an external control signal; and   means to limit to a predetermined timeout the duration in time the suspension means can suspend said periodic update coupled to said means to suspend..]..[.2. The oscillator of claim 1, wherein:   the frequency generation means comprises a piezoelectric crystal oscillator having a bank of trimming capacitors controlled by switches such that a digital code presented to said switches will cause said crystal oscillator to vary in output frequency..]..[.3. The oscillator of claim 1, wherein:   the temperature detecting means comprises an ambient temperature sensor and a analog-to-digital converter connected to the frequency adjusting means..]..[.4. The oscillator of claim 1, wherein:   the frequency adjusting means comprises a programmable read only memory responsive to the temperature detecting means and a latch connected to the frequency generating means..]..[.5. A digitally-corrected temperature compensated crystal oscillator (DTCXO) having an output and a control input, comprising:   means for generating a free-running frequency signal connected to the output, comprising a piezoelectric crystal oscillator having a bank of trimming capacitors controlled by switches such that a digital code presented to said switches will cause said DTCXO to vary in output frequency;   means for detecting an ambient temperature proximate to the frequency generating means, comprising an ambient temperature sensor and a analog-to-digital converter;   means for adjusting said free-running frequency signal responsive to the detection means and connected to the frequency generating means, comprising a programmable read only memory responsive to the temperature detecting means and a latch connected to the frequency generating means; and   means to suspend the adjusting means such that a last valid adjustment value is held during a period of suspension, the suspension means responsive to the control input and connected to the frequency adjusting means..]..[.6. The DTCXO of claim 5, further comprising:   means to periodically disable the suspension means upon the occurrence and reoccurrence of a predetermined timeout responsive to the suspension means and a timer..]..[.7. A radio communications unit, comprising:   at least one digitally-corrected temperature-compensated crystal oscillator (DTCXO) having an output and a control input, having: (a) means for generating a free-running frequency signal connected to the output, comprising a piezoelectric crystal oscillator having a bank of trimming capacitors controlled by switches such that a digital code presented to said switches will cause said DTCXO to vary in output frequency;   (b) means for detecting an ambient temperature proximate to the frequency generating means, comprising an ambient temperature sensor and a analog-to-digital converter;   (c) means for adjusting said free-running frequency signal responsive to the detection means and connected to the frequency generating means, comprising a programmable read only memory responsive to the temperature detecting means and a latch connected to the frequency generating means; and   (d) means to suspend the adjusting means such that a last valid adjustment value is held during a period of suspension, the suspension means responsive to the control input and connected to the frequency adjusting means.     means for receiving communications responsive to a signal from the DTCXO..]..[.8. The unit of claim 7, further comprising:   means for transmitting communications responsive to a signal from the DTCXO..]..[.9. The unit of claim 7, further comprising:   a microprocessor connected such that said DTCXO control input is manipulated in response to a plurality of operating modes existing in the radio communications unit..]..[.10. A method for improving the quality of electronic telecommunications in a multi-mode communication means utilizing an oscillator having a temperature compensation means to update a value based upon detected temperature at said oscillator and, via adjustment means, change the frequency of oscillation of said oscillator to a predetermined frequency of oscillation based upon said updated value, comprising the steps of:   detecting which, if any, modes of electronic telecommunication are active;   suspending the updating by said temperature compensation means upon detection of an active mode to prevent said updating from generating interference that can degrade the operation of the active mode of said communications means;   providing a delay period commencing from the point in time when updating last occurred; and   updating said temperature compensation means value after the expiration of the delay period whether or not an active mode is detected..]..[.11. The method of claim 10, wherein:   said modes comprise transmission, message encoding, reception, and message decoding..]..[.12. A method for improving the quality of communications in a cellular telephone having modes comprising transmission, message encoding, reception, and message decoding, the telephone utilizing an oscillator having a temperature compensation means to update a value based upon detected temperature at said oscillator and, via adjustment means, change the frequency of oscillation of said oscillator to a predetermined frequency of oscillation based upon said updated value, comprising the steps of:   detecting which, if any, modes of electronic telecommunication are active;   suspending the updating by said temperature compensation means upon detection of an active mode to prevent said updating from generating interference that can degrade the operation of the active mode of said cellular telephone;   providing a delay period commencing from the point in time when updating last occurred; and   updating said temperature compensation means value after the expiration of the delay period whether or not an active mode is detected..]..[.13. A computer-implemented process for improving electronic communications in a radio having a microprocessor, comprising the following steps:   detecting whether or not at least one mode of electronic communication is active, said modes comprising transmission, message encoding, reception, and message decoding;   suspending an updating of a temperature compensation correction word in an oscillator system providing reference frequencies that are supporting said electronic communications, such that interference and errors otherwise generated by said updating of said temperature compensation correction word will not be induced during the time activity of said mode is detected; and   waiting a timeout period from a point of last inactivity of said mode and then forcing the updating of said temperature compensation correction word in said oscillator system..]..[.14. A method for improving receiver sensitivity and for reducing power consumption in a telephone pager utilizing an oscillator having a temperature compensation means to update a value based upon detected temperature at said oscillator and, via adjustment means, change the frequency of oscillation of said oscillator to a predetermined frequency of oscillation based upon said updated value, comprising the steps of:   detecting when the pager is in a standby mode of operation;   suspending the updating by said temperature compensation means upon detection of said standby mode to prevent said temperature compensation updating means from generating interference that can deteriorate the receiver sensitivity of the pager and from consuming power;   providing a delay period commencing from the point in time when updating last occurred; and   updating said temperature compensation means value after the expiration of   
     
     
        the delay period whether or not an active mode is detected..]..Iadd.15.  A digitally-corrected, temperature-compensated crystal oscillator circuit having an output terminal and a control input terminal inputting an external control signal indicating a state of a communication circuit, said digitally-corrected, temperature-compensated crystal oscillator circuit, comprising: an oscillator circuit generating a frequency signal, the frequency signal output on the output terminal;   a compensation circuit connected to the oscillator, wherein a frequency of the frequency signal is based on a state of the compensation circuit;   a temperature sensor circuit detecting an ambient temperature and outputting a temperature signal based on the detected ambient temperature;   a conversion circuit connected to the temperature sensor circuit and the compensation circuit and inputting the temperature signal and outputting a ready signal and a compensation signal, the state of the compensation circuit based on the compensation signal; and   a control circuit connected to the conversion circuit and inputting the external control signal and outputting a control signal to the conversion circuit only when the external control signal indicates that the communication circuit is not active and the ready signal is generated by the conversion circuit, the conversion circuit updating the compensation signal based on the control signal..Iaddend..Iadd.16. The digitally-corrected, temperature-compensated crystal oscillator circuit of claim 15, wherein the temperature sensor is in thermal proximity to the oscillator circuit..Iaddend..Iadd.17. The digitally-corrected, temperature-compensated crystal oscillator circuit of claim 15, wherein the control circuit comprises a timer circuit, wherein, when the timer circuit times out, the control circuit operates the conversion circuit to update the compensation signal independently of the sate of the external control signal..Iaddend..Iadd.18. The digitally-corrected, temperature-compensated crystal oscillator circuit of claim 15, wherein the conversion circuit comprises:   a memory device storing a temperature conversion table, wherein the memory device inputs the temperature signal as an address and outputs the compensation signal; and   a latch circuit for latching the compensation signal based on the control signal output by the control circuit..Iaddend..Iadd.19. The digitally-corrected, temperature-compensated crystal oscillator circuit of claim 15, wherein the temperature sensor circuit comprises:   a temperature sensing device outputting an analog temperature signal; and   an analog-to-digital converter inputting the analog temperature signal and outputting a digital temperature signal as the temperature signal to the conversion circuit..Iaddend..Iadd.20. The digitally-corrected, temperature-compensated crystal oscillator circuit of claim 15, wherein the compensation circuit comprises:   a switching circuit, comprising a plurality of switches, and inputting the compensation signal, a state of each switch based on the compensation signal; and   a capacitor trimming circuit comprising a plurality of capacitors, each capacitor connected to a corresponding one of the plurality of switches of the switching circuit, each one of the plurality of capacitors switched in and out of the capacitor trimming circuit based on the state of the corresponding switch, wherein a total effective capacitance of the capacitor trimming circuit is based on which capacitors are switched in, the total effective capacitance adjusting the frequency of the signal output by the oscillator circuit..Iaddend..Iadd.21. The digitally-corrected, temperature-compensated crystal oscillator circuit of claim 15, wherein the compensation circuit comprises at least one varactor, a state of each at least one varactor based on the compensation signal..Iaddend..Iadd.22. The digitally-corrected, temperature-compensated crystal oscillator circuit of claim 15, wherein the oscillator circuit comprises a piezoelectric crystal oscillator..Iaddend..Iadd.23. A communication unit, comprising:   an oscillator circuit outputting a pulse signal;   a temperature sensor circuit outputting a temperature signal indicative of a sensed temperature;   a temperature conversion circuit outputting a ready signal and a temperature compensation signal based on the temperature signal;   a temperature compensation circuit, wherein a state of the temperature compensation circuit is based on the temperature compensation signal, the state of the temperature compensation circuit adjusting a frequency of the pulse signal output by the oscillator circuit; and   a communication circuit inputting the pulse signal, wherein based on an operating state of the communication circuit and generation of the ready signal by the temperature conversion circuit, an update of the adjustment of the frequency of the pulse signal by the temperature compensation   
     
     
        circuit is suspended..Iaddend..Iadd.24.  The communications unit of claim 23, wherein the temperature sensor circuit is in thermal proximity to the oscillator circuit..Iaddend..Iadd.25. The communication unit of claim 23, further comprising a control circuit inputting an external control signal indicative of the operating state of the communication circuit and outputting a control signal, based on the state of the external control signal, to the temperature conversion circuit to cause the temperature conversion circuit to output the temperature compensation signal, the control circuit including a timer circuit, wherein, when the timer circuit times out, the control circuit outputs the control signal to the temperature conversion circuit independently of the state of the external control signal..Iaddend..Iadd.26. The communications unit of claim 23, wherein the temperature conversion circuit comprises: a memory device storing a temperature conversion table, wherein the memory device inputs the temperature signal as an address and outputs the temperature compensation signal; and a latch circuit for latching the temperature compensation signal based on the control signal output by the control circuit..Iaddend..Iadd.27. The communications unit of claim 26, wherein the temperature compensation circuit further comprises:   a switching circuit, comprising a plurality of switches, and inputting the temperature compensation signal, a state of each switch based on the temperature compensation signal; and   a capacitor trimming circuit comprising a plurality of capacitors, each capacitor connected to a corresponding one of the plurality of switches of the switching circuit, each one of the plurality of capacitors switched in and out of the capacitor trimming circuit based on the state of the corresponding switch, wherein a total effective capacitance of the capacitor trimming circuit is based on which capacitors are switched in, the total effective capacitance adjusting the frequency of the pulse signal output by the oscillator circuit..Iaddend..Iadd.28. The communications unit of claim 26, wherein the temperature compensation circuit further comprises at least one varactor, a state of each at least one varactor based on the temperature compensation signal..Iaddend..Iadd.29. The communications unit of claim 23, wherein the temperature sensor circuit comprises:   a temperature sensing device outputting an analog temperature signal; and   an analog-to-digital converter inputting the analog temperature signal and outputting a digital temperature signal as the temperature signal to the temperature conversion circuit..Iaddend..Iadd.30. The communication unit of claim 23, wherein the oscillator circuit comprises a piezoelectric crystal oscillator..Iaddend..Iadd.31. The communications unit of claim 23, wherein the communications circuit comprises at least one of a receiving   
     
     
        circuit and a transmitting circuit..Iaddend..Iadd.32.  The communication unit of claim 23, wherein the temperature compensation circuit periodically adjusts the frequency of the pulse signal output by the oscillator circuit..Iaddend..Iadd.33. The communication unit of claim 23, wherein the communication circuit is a radio communication 
     
     
        circuit..Iaddend..Iadd.34.  The communication unit of claim 23, wherein the communication circuit is a wire communication circuit..Iaddend..Iadd.35. A communications unit, comprising: an oscillator circuit outputting pulse signal;   a communications circuit inputting the pulse signal of the oscillator circuit, wherein the communications circuit alternates, periodically, between a receive state and a standby state, the communications circuit outputting an external control signal based on the state of the communications circuit;   a temperature sensor circuit outputting a temperature signal indicative of a sensed temperature;   a temperature conversion circuit inputting the temperature signal and outputting a ready signal and a temperature compensation signal based on the temperature signal;   a temperature compensation circuit, wherein a state of the temperature compensation circuit is based on the temperature compensation signal, the state of the temperature compensation circuit adjusting a frequency of the pulse signal output by the oscillator circuit; and   a control circuit inputting the external control signal and outputting a control signal to the temperature conversion circuit to operate the temperature conversion circuit to update the state of the temperature compensation circuit only when the communications circuit is in the standby state and the ready signal is generated by the temperature conversion circuit, wherein the control circuit is prevented from outputting the control signal to the temperature conversion circuit when the external control signal indicates that the communications circuit is in the receive state..Iaddend..Iadd.36. A time division multiple access communications unit, comprising:   an oscillator circuit outputting a pulse signal;   a time division multiple access communications circuit inputting the pulse signal of the oscillator circuit, wherein the communications circuit has receive operation periods, send operation periods, and idle periods, the communications circuit outputting an external control signal;   a temperature sensor circuit outputting a temperature signal indicative of a sensed temperature;   a temperature conversion circuit outputting a ready signal and a temperature compensation signal based on the temperature signal;   a temperature compensation circuit, wherein a state of the temperature compensation circuit is based on the temperature compensation signal, the state of the temperature compensation circuit adjusting a frequency of the pulse signal output by the oscillator circuit; and   a control circuit inputting the external control signal and outputting a control signal to the temperature conversion circuit to operate the temperature conversion circuit to update the state of the temperature compensation circuit only when the communications circuit is in said idle periods and the ready signal is generated by the temperature conversion circuit, wherein the control circuit is prevented from outputting the control signal to the temperature conversion circuit when the external control signal indicates that the communications circuit is in one of a receive operation period or a send operation period..Iaddend..Iadd.37. A compensated oscillator, comprising:   an oscillator circuit outputting a pulse signal;   a compensation signal generating circuit outputting a compensation signal and a ready signal;   a compensation circuit, wherein a state of the compensation circuit is based on the compensation signal, the state of the compensation circuit adjusting a frequency of the pulse signal output by the oscillator circuit; and   a control circuit inputting an external control signal and outputting a control signal to the compensation signal generating circuit to operate the compensation signal generating circuit to output the compensation signal to update the state of the compensation circuit, wherein, the control circuit is prevented from outputting the control signal when the external control signal indicates that a communication circuit that uses said pulse signal is active and the ready signal is not generated by the compensation signal generating circuit..Iaddend..Iadd.38. A communication unit, comprising:   an oscillator circuit outputting a pulse signal;   a compensation signal generating circuit outputting a compensation signal and a ready signal;   a compensation circuit, wherein a state of the compensation circuit is based on the compensation signal, the state of the compensation circuit adjusting a frequency of the pulse signal output by the oscillator circuit; and   a communication circuit inputting the pulse signal, wherein, based on an operating state of the communication circuit and generation of the ready signal by the compensation signal generating circuit, an update of the adjustment of the frequency is suspended..Iaddend.