초록 ▼

Frequency modification circuitry may be employed as part of a crystal oscillator circuit to generate a reference signal with adjustable frequency. The frequency modification circuitry may be implemented as part of a crystal oscillator circuit that includes digitally controlled crystal oscillator ("D

Frequency modification circuitry may be employed as part of a crystal oscillator circuit to generate a reference signal with adjustable frequency. The frequency modification circuitry may be implemented as part of a crystal oscillator circuit that includes digitally controlled crystal oscillator ("DCXO") circuitry and a crystal. The frequency modification circuitry may adjust the frequency of the reference signal in response to one or more frequency control signals. In one example, the frequency modification circuitry may include variable capacitors such as one or more continuously variable and/or discretely variable capacitors for providing coarse and/or fine adjustment of the reference signal frequency.

대표청구항 ▼

We claim: 1. A circuit for providing an adjustable reference signal to radio frequency (RF) circuitry, said circuit comprising: frequency modification circuitry comprising at least one variable capacitance device, said frequency modification circuit being configured for coupling to a crystal to for

We claim: 1. A circuit for providing an adjustable reference signal to radio frequency (RF) circuitry, said circuit comprising: frequency modification circuitry comprising at least one variable capacitance device, said frequency modification circuit being configured for coupling to a crystal to form a crystal oscillator circuit that is capable of providing said adjustable reference signal to at least one component of said RF circuitry; wherein said at least one variable capacitance device is configured to adjust the frequency of said adjustable reference signal; wherein said at least one variable capacitance device is configured to adjust the frequency of said adjustable reference signal based at least in part on at least one frequency control signal received by said frequency modification circuitry; and wherein said variable capacitance device comprises: variable capacitor circuitry configured to adjust the frequency of said adjustable reference signal in response to a plurality of control voltage signals, and control circuitry, the control circuitry configured to generate the plurality of control voltage signals in response to said at least one frequency control signal received by said frequency modification circuitry, wherein the voltage level of each of the plurality of the control voltage signals differs by an offset voltage from the voltage level of the remaining signals in the plurality of control voltage signals. 2. The circuit of claim 1, wherein said control circuitry comprises a signal generator circuit adapted to generate the plurality of control signals having respective levels that are progressively offset from said at least one frequency control signal. 3. The circuit of claim 1, wherein said variable capacitance device comprises a plurality of capacitor stages coupled in parallel. 4. The circuit of claim 3, wherein each of the plurality of capacitor stages comprises a first fixed capacitor coupled to a second fixed capacitor; wherein said variable capacitance device further comprises a plurality of variable impedance devices, each of the plurality of variable impedance devices being coupled in parallel with the second capacitor in a respective one of the plurality of capacitor stages; and wherein each of the plurality of control signals controls a respective variable impedance device in the plurality of variable impedance devices. 5. The circuit of claim 4, wherein said at least one frequency control signal comprises a voltage signal. 6. The circuit of claim 4, wherein said at least one frequency control signal comprises a current signal. 7. A circuit for providing an adjustable reference signal to radio frequency (RF) circuitry, said circuit comprising: frequency modification circuitry comprising at least one variable capacitance device, said frequency modification circuit being configured for coupling to a crystal to form a crystal oscillator circuit that is capable of providing said adjustable reference signal to at least one components of said RF circuitry; wherein said at least one variable capacitance device is configured to adjust the frequency of said adjustable reference signal; wherein said at least one variable capacitance device is configured to adjust the frequency of said adjustable reference signal based at least in part on at least one frequency control signal received by said frequency modification circuitry; and wherein said variable capacitance device comprises a digitally programmable capacitor array configured to adjust the frequency of said adjustable reference signal in response to a plurality of frequency control signal generated by a digitally programmable capacitor array register. 8. The circuit of claim 7, wherein said digitally programmable capacitor array comprises a plurality of capacitor stages coupled in parallel. 9. The circuit of claim 8, wherein each of the plurality of capacitor stages comprises a fixed capacitor; wherein said digitally programmable capacitor array further comprises a plurality of transistors, each of the plurality of transistors being coupled in series with the fixed capacitor in a respective one of the plurality of capacitor stages; and wherein each of the plurality of control signal controls a respective transistor in the plurality of transistors. 10. The circuit of claim 9, wherein said at least one frequency control signal comprises multiple bits of a digital signal. 11. A circuit for providing an adjustable reference signal to radio frequency (RF) circuitry, said circuit comprising: frequency modification circuitry comprising at least one variable capacitance device, said frequency modification circuit being configured for coupling to a crystal to form a crystal oscillator circuit that is capable of providing said adjustable reference signal to at least one component of said RF circuitry; wherein said at least one variable capacitance device is configured to adjust the frequency of said adjustable reference signal; wherein said at least one variable capacitance device is configured to adjust the frequency of said adjustable reference signal based at least in part on at least one frequency control signal received by said frequency modification circuitry; wherein said at least one variable capacitance device comprises at least one continuously variable capacitor, and wherein said at least one frequency control signal comprises at least one analog signal; and wherein said at least one frequency control signal received by said frequency modification circuitry comprises at least one adjusted frequency control signal; and wherein said circuit further comprises interface circuitry configured to receive at least one raw frequency control signal and to adjust the voltage of said at least one raw frequency control signal to produce said at least one adjusted frequency control signal. 12. The circuit of claim 11, wherein at least part of the voltage range of said at least one raw frequency control signal has a voltage magnitude that is not within the operating range of said variable capacitance device; and wherein said interface circuitry is configured to adjust the voltage magnitude of said at least one raw frequency control signal to produce an adjusted frequency control signal having a voltage range that is within the operating range of said variable capacitance device. 13. A communication device, comprising: RF circuitry, said RF circuitry comprising at least one of transmitter circuitry, receiver circuitry, or a combination thereof; and frequency modification circuitry comprising at least one variable capacitance device, said frequency modification circuit being configured for coupling to a crystal to form a crystal oscillator circuit that is capable of providing an adjustable reference signal to at least one of said transmitter circuitry, receiver circuitry, or a combination thereof; wherein said at least one variable capacitance device is configured to adjust the frequency of said adjustable reference signal; wherein said at least one variable capacitance device of said frequency modification circuitry is configured to adjust the frequency of said adjustable reference signal based at least in part on at least one frequency control signal received by said frequency modification circuitry; wherein said communication device further comprises baseband processor circuitry coupled to said frequency modification circuitry, said baseband processor circuitry being configured to provide said at least one frequency control signal to said frequency modification circuitry; and wherein said variable capacitance device comprises: variable capacitor circuitry configured to adjust the frequency of said adjustable reference signal in response to a plurality of control voltage signals; and control circuitry, the control circuitry configured to generate the plurality of control voltage signals in response to said at least one frequency control signal; wherein the voltage level of each of the plurality of the control voltage signals differs by an offset voltage from the voltage level of the remaining signals in the plurality of control voltage signals. 14. The communication device of claim 13, wherein said variable capacitance device comprises a plurality of capacitor stages coupled in parallel, each of the plurality of capacitor stages comprises a first fixed capacitor coupled to a second fixed capacitor; wherein said variable capacitance device further comprises a plurality of variable impedance devices, each of the plurality of variable impedance devices being coupled in parallel with the second capacitor in a respective one of the plurality of capacitor stages; and wherein each of the plurality of control signal controls a respective variable impedance device in the plurality of variable impedance devices. 15. A communication device, comprising: RF circuitry, said RF circuitry comprising at least one of transmitter circuitry, receiver circuitry, or a combination thereof; and frequency modification circuitry comprising at least one variable capacitance device, said frequency modification circuit being configured for coupling to a crystal to form a crystal oscillator circuit that is capable of providing an adjustable reference signal to at least one of said transmitter circuitry, receiver circuitry, or a combination thereof; wherein said at least one variable capacitance device is configured to adjust the frequency of said adjustable reference signal; wherein said at least one variable capacitance device of said frequency modification circuitry is configured to adjust the frequency of said adjustable reference signal based at least in part on at least one frequency control signal received by said frequency modification circuitry; wherein said communication device further comprises baseband processor circuitry coupled to said frequency modification circuitry, said baseband processor circuitry being configured to provide said at least one frequency control signal to said frequency modification circuitry; and wherein said variable capacitance device comprises a digitally programmable capacitor array configured to adjust the frequency of said adjustable reference signal in response to a plurality of frequency control signal generated by a digitally programmable capacitor array register. 16. The communication device of claim 15, wherein said digitally programmable capacitor array comprises a plurality of capacitor stages coupled in parallel, each of the plurality of capacitor stages comprising a fixed capacitor; wherein said digitally programmable capacitor array further comprises a plurality of transistors, each of the plurality of transistors being coupled in series with the fixed capacitor in a respective one of the plurality of capacitor stages; and wherein each of the plurality of control signal controls a respective transistor in the plurality of transistors. 17. A communication device, comprising: RF circuitry, said RF circuitry comprising at least one of transmitter circuitry, receiver circuitry, or a combination thereof; and frequency modification circuitry comprising at least one variable capacitance device, said frequency modification circuit being configured for coupling to a crystal to form a crystal oscillator circuit that is capable of providing an adjustable reference signal to at least one of said transmitter circuitry, receiver circuitry, or a combination thereof; wherein said at least one variable capacitance device is configured to adjust the frequency of said adjustable reference signal; wherein said at least one variable capacitance device of said frequency modification circuitry is configured to adjust the frequency of said adjustable reference signal based at least in part on at least one frequency control signal received by said frequency modification circuitry; wherein said at least one frequency control signal received by said frequency modification circuitry comprises at least one adjusted frequency control signal; and wherein said communication device further comprises: baseband processor circuitry configured to provide at least one raw frequency control signal, and interface circuitry coupled to said baseband processor circuitry and to said frequency modification circuitry, said interface circuitry being configured to receive said at least one raw frequency control signal from said baseband processor circuitry and to adjust the voltage of said at least one raw frequency control signal to produce said at least one adjusted frequency control signal and to provide said at least one adjusted frequency control signal to said frequency modification circuitry. 18. The Communication device of claim 17, wherein at least part of the voltage range of said at least one raw frequency control signal provided by said baseband processor circuitry has a voltage magnitude that is not within the operating range of said variable capacitance device; and wherein said interface circuitry is configured to adjust the voltage magnitude of said at least one raw frequency control signal to produce an adjusted frequency control signal having a voltage range that is within the operating range of said variable capacitance device. 19. A method of operating a crystal oscillator circuit to provide an adjustable reference signal to radio frequency (RF) circuitry, comprising: generating said adjustable reference signal using said crystal oscillator circuit, said crystal oscillator circuit comprising frequency modification circuitry that comprises at least one variable capacitance device and a crystal coupled to said frequency modification circuitry; adjusting the frequency of said adjustable reference signal using said variable capacitance device; and providing said adjustable reference signal to at least one component of said RF circuitry; wherein said method further comprises adjusting the frequency of said adjustable reference signal using said variable capacitance device based at least in part on at least one frequency control signal received by said frequency modification circuitry; wherein said frequency modification circuitry comprises at least one continuously variable capacitor and at least one discretely variable capacitor, and wherein said method further comprises adjusting the frequency of said adjustable reference signal using said at least one continuously variable capacitor and using said at least one discretely variable capacitor in response to said at least one frequency control signal received by said frequency modification circuitry; and wherein said frequency modification circuitry comprises at least one continuously variable capacitor and at least one discretely variable capacitor, and wherein said method further comprises first adjusting the frequency of said adjustable reference signal using said at least one discretely variable capacitor in response to said at least one frequency control signal received by said frequency modification circuitry; and then further adjusting the frequency of said adjustable reference signal using said at least one continuously variable capacitor in response to said at least one frequency control signal received by said frequency modification circuitry. 20. A method of operating a crystal oscillator circuit to provide an adjustable reference signal to radio frequency (RF) circuitry, comprising: generating said adjustable reference signal using said crystal oscillator circuit, said crystal oscillator circuit comprising frequency modification circuitry that comprises at least one variable capacitance device and a crystal coupled to said frequency modification circuitry; adjusting the frequency of said adjustable reference signal using said variable capacitance device; and providing said adjustable reference signal to one or more components of said RF circuitry; wherein said method further comprises adjusting the frequency of said adjustable reference signal using said variable capacitance device based at least in part on at least one frequency control signal received by said frequency modification circuitry; wherein said method further comprises: generating a plurality of control voltage signals in response to said at least one frequency control signal received by said frequency modification circuitry, wherein the voltage level of each of the plurality of the control voltage signals differs by an offset voltage from the voltage level of the remaining signals in the plurality of control voltage signals; and adjusting the frequency of said adjustable reference signal in response to said plurality of control voltage signals. 21. The method of claim 20, further comprising generating said plurality of control signals to have respective levels that are progressively offset from said at least one frequency control signal. 22. The method of claim 20, wherein said variable capacitance device comprises a plurality of capacitor stages coupled in parallel, each of the plurality of capacitor stages comprising a first fixed capacitor coupled to a second fixed capacitor; wherein said variable capacitance device further comprises a plurality of variable impedance devices, each of the plurality of variable impedance devices being coupled in parallel with the second capacitor in a respective one of the plurality of capacitor stages; and wherein said method further comprises using each of the plurality of control signals to control a respective variable impedance device in the plurality of variable impedance devices. 23. A method of operating a crystal oscillator circuit to provide an adjustable reference signal to radio frequency (RF) circuitry, comprising: generating said adjustable reference signal using said crystal oscillator circuit, said crystal oscillator circuit comprising frequency modification circuitry that comprises at least one variable capacitance device and a crystal coupled to said frequency modification circuitry; adjusting the frequency of said adjustable reference signal using said variable capacitance device; and providing said adjustable reference signal to at least one component of said RF circuitry; wherein said method further comprises adjusting the frequency of said adjustable reference signal using said variable capacitance device based at least in part on at least one frequency control signal received by said frequency modification circuitry; and wherein said method further comprises adjusting the frequency of said adjustable reference signal in response to said plurality of frequency control signals using a digitally programmable capacitor array. 24. The method of claim 23, wherein said digitally programmable capacitor array comprises a plurality of capacitor stages coupled in parallel, wherein each of the plurality of capacitor stages comprises a fixed capacitor; wherein said digitally programmable capacitor array further comprises a plurality of transistors, each of the plurality of transistors being coupled in series with the fixed capacitor in a respective one of the plurality of capacitor stages; and wherein said method further comprises using each of the plurality of control signals to control a respective transistor in the plurality of transistors. 25. The method of claim 24, wherein said at least one frequency control signal comprises multiple bits of a digital signal. 26. A method of operating a crystal oscillator circuit to provide an adjustable reference signal to radio frequency (RF) circuitry, comprising: generating said adjustable reference signal using said crystal oscillator circuit, said crystal oscillator circuit comprising frequency modification circuitry that comprises at least one variable capacitance device and a crystal coupled to said frequency modification circuitry; adjusting the frequency of said adjustable reference signal using said variable capacitance device; and providing said adjustable reference signal to at least one component of said RF circuitry; wherein said method further comprises adjusting the frequency of said adjustable reference signal using said variable capacitance device based at least in part on at least one frequency control signal received by said frequency modification circuitry; wherein said at least one variable capacitance device comprises at least one continuously variable capacitor, and wherein said at least one frequency control signal comprises at least one analog signal; wherein said at least one frequency control signal received by said frequency modification circuitry comprises at least one adjusted frequency control signal; and wherein said method further comprises adjusting the voltage of at least one raw frequency control signal to produce said at least one adjusted frequency control signal, and adjusting the frequency of said adjustable reference signal using said variable capacitance device based at least in part on said at least one adjusted frequency control signal. 27. The method of claim 26, wherein at least part of the voltage range of said at least one raw frequency control signal has a voltage magnitude that is not within the operating range of said variable capacitance device; and wherein said method further comprises adjusting the voltage magnitude of said at least one raw frequency control signal to produce an adjusted frequency control signal having a voltage range that is within the operating range of said variable capacitance device. 28. A method of operating a radio-frequency (RF) device, comprising: generating an adjustable reference signal using a crystal oscillator circuit, said crystal oscillator circuit comprising frequency modification circuitry that comprises at least one variable capacitance device and a crystal coupled to said frequency modification circuitry; adjusting the frequency of said adjustable reference signal using said variable capacitance device; and providing said adjustable reference signal or a signal based on said adjustable reference signal to at least one RF circuitry component of said RF device, said at least one RF circuitry component comprising transmitter circuitry, receiver circuitry, or a combination thereof; wherein said method further comprises adjusting the frequency of said adjustable reference signal using said variable capacitance device based at least in part on at least one frequency control signal received by said frequency modification circuitry; wherein said method further comprises receiving said at least one frequency control signal in said frequency modification circuitry, said frequency control signal comprising at least one signal provided from baseband processor circuitry coupled to said crystal oscillator circuit or comprising at least one signal based on at least one signal provided from baseband processor circuitry coupled to said crystal oscillator circuit; and wherein said method further comprises: generating a plurality of control voltage signals in response to said at least one frequency control signal received by said frequency modification circuitry, wherein the voltage level of each of the plurality of the control voltage signals differs by an offset voltage from the voltage level of the remaining signals in the plurality of control voltage signals, and adjusting the frequency of said adjustable reference signal in response to said plurality of control voltage signals. 29. The method of claim 28, wherein said variable capacitance device comprises a plurality of capacitor stages coupled in parallel, each of the plurality of capacitor stages comprising a first fixed capacitor coupled to a second fixed capacitor; wherein said variable capacitance device further comprises a plurality of variable impedance devices, each of the plurality of variable impedance devices being coupled in parallel with the second capacitor in a respective one of the plurality of capacitor stages; and wherein said method further comprises using each of the plurality of control signals to control a respective variable impedance device in the plurality of variable impedance devices. 30. A method of operating a radio-frequency (RF) device, comprising: generating an adjustable reference signal using a crystal oscillator circuit, said crystal oscillator circuit comprising frequency modification circuitry that comprises at least one variable capacitance device and a crystal coupled to said frequency modification circuitry; adjusting the frequency of said adjustable reference signal using said variable capacitance device; and providing said adjustable reference signal or a signal based on said adjustable reference signal to at least one RF circuitry component of said RF device, said at least one RF circuitry component comprising transmitter circuitry, receiver circuitry, or a combination thereof; wherein said method further comprises adjusting the frequency of said adjustable reference signal using said variable capacitance device based at least in part on at least one frequency control signal received by said frequency modification circuitry; wherein said method further comprises receiving said at least one frequency control signal in said frequency modification circuitry, said frequency control signal comprising at least one signal provided from baseband processor circuitry coupled to said crystal oscillator circuit or comprising at least one signal based on at least one signal provided from baseband processor circuitry coupled to said crystal oscillator circuit; and wherein said method further comprises adjusting the frequency of said adjustable reference signal in response to said plurality of frequency control signals using a digitally programmable capacitor array. 31. The method of claim 30, wherein said digitally programmable capacitor array comprises a plurality of capacitor stages coupled in parallel, wherein each of the plurality of capacitor stages comprises a fixed capacitor; wherein said digitally programmable capacitor array further comprises a plurality of transistors, each of the plurality of transistors being coupled in series with the fixed capacitor in a respective one of the plurality of capacitor stages; and wherein said method further comprises using each of the plurality of control signals to control a respective transistor in the plurality of variable transistors. 32. A method of operating a radio-frequency (RF) device, comprising: generating an adjustable reference signal using a crystal oscillator circuit, said crystal oscillator circuit comprising frequency modification circuitry that comprises at least one variable capacitance device and a crystal coupled to said frequency modification circuitry; adjusting the frequency of said adjustable reference signal using said variable capacitance device; and providing said adjustable reference signal or a signal based on said adjustable reference signal to at least one RF circuitry component of said RF device, said at least one RF circuitry component comprising transmitter circuitry, receiver circuitry, or a combination thereof; wherein said method further comprises adjusting the frequency of said adjustable reference signal using said variable capacitance device based at least in part on at least one frequency control signal received by said frequency modification circuitry; wherein said at least one frequency control signal received by said frequency modification circuitry comprises at least one adjusted frequency control signal; and wherein said method further comprises receiving at least one raw frequency control signal from baseband processor circuitry, adjusting the voltage of said at least one raw frequency control signal to produce said at least one adjusted frequency control signal, and adjusting the frequency of said adjustable reference signal using said variable capacitance device based at least in part on said at least one adjusted frequency control signal. 33. The method of claim 32, wherein at least part of the voltage range of said at least one raw frequency control signal received from said baseband processor circuitry has a voltage magnitude that is not within the operating range of said variable capacitance device; and wherein said method further comprises adjusting the voltage magnitude of said at least one raw frequency control signal to produce an adjusted frequency control signal having a voltage range that is within the operating range of said variable capacitance device.