Frequency modification circuitry for use in radio-frequency communication apparatus and associated methods

• US 7,200,364 B2
• Filed: 12/23/2005
• Issued: 04/03/2007
• Est. Priority Date: 05/29/1998
• Status: Expired due to Fees

• Current Assignee: Silicon Laboratories Incorporated
• Original Assignee: Silicon Laboratories Incorporated
• Inventors: Lim, Lysander, Maligeorgos, James
• Primary Examiner(s): Gesesse; Tilahun
• Application Number:
  US11/318,277
• Publication Number:
  US 20060160512A1
• Time in Patent Office: 466 Days
• Field of Search: 455/76, 455/260, 455/147, 455/113, 455/183.1, 331/36.V, 331/36.R, 331/117.R, 331/117.V
• US Class Current: 455/76
• CPC Class Codes: H03B 5/366 and comprising means for varying the frequency by a variable voltage or current
• CPC Class Codes: H03L 7/085 concerning mainly the frequency- or phase-detection arrangement including the filtering or amplification of its output signal H03L7/10 takes precedence; circuits for comparing the phase or frequency of two mutually-independent oscillations H03D13/00
• CPC Class Codes: H03L 7/087 using at least two phase detectors or a frequency and phase detector in the loop
• CPC Class Codes: H03L 7/091 the phase or frequency detector using a sampling device H03L7/087 takes precedence
• CPC Class Codes: H03L 7/099 concerning mainly the controlled oscillator of the loop
• CPC Class Codes: H03L 7/187 using means for coarse tuning the voltage controlled oscillator of the loop H03L7/191 - H03L7/195 take precedence
• CPC Class Codes: H03L 7/199 with reset of the frequency divider or the counter, e.g. for assuring initial synchronisation
• CPC Class Codes: H03L 7/23 with pulse counters or frequency dividers
• CPC Class Codes: H04B 1/0003 Software-defined radio [SDR] systems, i.e. systems wherein components typically implemented in hardware, e.g. filters or modulators/demodulators, are implented using software, e.g. by involving an AD or DA conversion stage such that at least part of the signal processing is performed in the digital domain digital baseband systems H04L25/00; digital modulation/demodulation H04L27/00; CDMA H04B1/707; TDMA H04B7/2643; image transmission H04N5/00
• CPC Class Codes: H04B 1/28 the receiver comprising at least one semiconductor device having three or more electrodes
• CPC Class Codes: H04B 1/406 with more than one transmission mode, e.g. analog and digital modes
• CPC Class Codes: H04B 15/02 Reducing interference from electric apparatus by means located at or near the interfering apparatus
• CPC Class Codes: H04B 15/04 the interference being caused by substantially sinusoidal oscillations, e.g. in a receiver or in a tape-recorder
• CPC Class Codes: H04B 2215/064 Reduction of clock or synthesizer reference frequency harmonics

Abstract

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.

Claims

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 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;

wherein said frequency modification circuitry is integrated with RF transceiver circuitry, RF synthesizer circuitry, or a combination thereof; 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 signals.

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. The method of claim 1, wherein said frequency modification circuitry is integrated with RF transceiver circuitry.

8. The method of claim 1, wherein said frequency modification circuitry is integrated with RF synthesizer circuitry.

9. 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;

wherein said frequency modification circuitry is integrated with RF transceiver circuitry, RF synthesizer circuitry, or a combination thereof; 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 signals generated by a digitally programmable capacitor array register.

10. The circuit of claim 9, wherein said digitally programmable capacitor array comprises a plurality of capacitor stages coupled in parallel.

11. The circuit of claim 10, 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 signals controls a respective transistor in the plurality of transistors.

12. The circuit of claim 11, wherein said at least one frequency control signal comprises multiple bits of a digital signal.

13. The method of claim 9, wherein said frequency modification circuitry is integrated with RF transceiver circuitry.

14. The method of claim 9, wherein said frequency modification circuitry is integrated with RF synthesizer circuitry.

15. 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;

wherein said frequency modification circuitry is integrated with RF transceiver circuitry, RF synthesizer circuitry, or a combination thereof; and

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 signals 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.

16. The circuit of claim 15, 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.

17. The method of claim 15, wherein said at least one variable capacitance device further comprises a digitally programmable capacitor array configured to adjust the frequency of said adjustable reference signal in response to a plurality of frequency control signals generated by a digitally programmable capacitor array register.

18. The method of claim 17, wherein said frequency modification circuitry is integrated with RF transceiver circuitry.

19. The method of claim 17, wherein said frequency modification circuitry is integrated with RF synthesizer circuitry.

20. 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 frequency modification circuitry is integrated with RF transceiver circuitry, RF synthesizer circuitry, or a combination thereof; 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.

21. The communication device of claim 20, 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 signals controls a respective variable impedance device in the plurality of variable impedance devices.

22. 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;

wherein said frequency modification circuitry is integrated with RF transceiver circuitry, RF synthesizer circuitry, or a combination thereof; 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 signals generated by a digitally programmable capacitor array register.

23. The communication device of claim 22, 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 signals controls a respective transistor in the plurality of transistors.

24. 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 signals received by said frequency modification circuitry comprises at least one adjusted frequency control signal;

wherein said frequency modification circuitry is integrated with RF transceiver circuitry, RF synthesizer circuitry, or a combination thereof; 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 signals to produce said at least one adjusted frequency control signals and to provide said at least one adjusted frequency control signals to said frequency modification circuitry.

25. The communication device of claim 24, wherein at least part of the voltage range of said at least one raw frequency control signals 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 signals to produce an adjusted frequency control signal having a voltage range that is within the operating range of said variable capacitance device.

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 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;

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 signals 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 signals received by said frequency modification circuitry; and

wherein said frequency modification circuitry is integrated with RF transceiver circuitry, RF synthesizer circuitry, or a combination thereof.

27. 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 frequency modification circuitry is integrated with RF transceiver circuitry, RF synthesizer circuitry, or a combination thereof; 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.

28. The method of claim 27, further comprising generating said plurality of control signals to have respective levels that are progressively offset from said at least one frequency control signal.

29. The method of claim 27, 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 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 is integrated with RF transceiver circuitry, RF synthesizer circuitry, or a combination thereof; 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 transistors.

32. The method of claim 31, wherein said at least one frequency control signals comprises multiple bits of a digital signal.

33. 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 signals received by said frequency modification circuitry comprises at least one adjusted frequency control signal;

wherein said frequency modification circuitry is integrated with RF transceiver circuitry, RF synthesizer circuitry, or a combination thereof; 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.

34. The method of claim 33, wherein at least part of the voltage range of said at least one raw frequency control signals 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.

35. 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;

wherein said frequency modification circuitry is integrated with RF transceiver circuitry, RF synthesizer circuitry, or a combination thereof; 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.

36. The method of claim 35, 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.

37. 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;

wherein said frequency modification circuitry is integrated with RF transceiver circuitry, RF synthesizer circuitry, or a combination thereof; 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.

38. The method of claim 37, 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.

39. 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;

wherein said frequency modification circuitry is integrated with RF transceiver circuitry, RF synthesizer circuitry, or a combination thereof; 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 signals 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.

40. The method of claim 39, 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.