CALIBRATION TECHNIQUES FOR FREQUENCY SYNTHESIZERS

• US 20080248771A1
• Filed: 06/17/2008
• Published: 10/09/2008
• Est. Priority Date: 03/06/2002
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Dunworth, Jeremy D., Walker, Brett C.
• Granted Patent: US 8,019,301 B2
• Time in Patent Office: Days
• US Class Current: 455/258
• CPC Class Codes: H03L 7/0898 the source or sink current values being variable H03L7/0896 takes precedence
• CPC Class Codes: H03L 7/099 concerning mainly the controlled oscillator of the loop
• CPC Class Codes: H03L 7/113 using frequency discriminator
• CPC Class Codes: H03L 7/199 with reset of the frequency divider or the counter, e.g. for assuring initial synchronisation

Abstract

In one embodiment, this disclosure describes a frequency synthesizer for use in a wireless communication device, or similar device that requires precision frequency synthesis but small amounts of noise. In particular, the frequency synthesizer may include a phase locked loop (PLL) and an integrated voltage controlled oscillator (VCO). The frequency synthesizer may implement one or more calibration techniques to quickly and precisely calibrate the VCO. In this manner, the analog gain of the VCO can be significantly reduced, which may improve performance of the wireless communication device. Also, the initial state of the PLL may be improved to reduce lock time of the PLL, which may enhance performance of the wireless communication device.

Claims

1. A frequency synthesizer comprising:

an oscillator including configurable circuitry that defines an initial frequency of the oscillator for an initial input parameter; and

a calibration unit that adjusts the configurable circuitry based on a comparison of a signal indicative of the oscillator and a signal indicative of a reference, wherein the calibration unit initializes the signals indicative of the oscillator and the reference so that the signals are substantially in phase.

2. The frequency synthesizer of claim 1, wherein the oscillator comprises a voltage controlled oscillator and the initial input parameter is an initial input voltage, and wherein the configurable circuitry comprises a number of switched capacitors, wherein the calibration unit adjusts the configurable circuitry by activating a subset of the switched capacitors based on the comparison of the signal indicative of the oscillator and the signal indicative of the reference.

3. The frequency synthesizer of claim 2, further comprising circuitry that generates the initial input voltage based on temperature.

4. The frequency synthesizer of claim 1, further comprising a first divider that generates the signal indicative of the oscillator by scaling an oscillator frequency defined by the initial input parameter, and a second divider that generates the signal indicative of the reference by scaling a reference frequency.

5. The frequency synthesizer of claim 4, wherein the calibration unit initializes the first and second dividers at approximately the same time to initialize signals indicative of the oscillator and the reference so that the signals are substantially in phase.

6. The frequency synthesizer of claim 4, further comprising a phase locked loop that provides analog control of the oscillator following calibration.

7. The frequency synthesizer of claim 6, wherein the phase locked loop and the oscillator are integrated as integrated circuitry, wherein the dividers used for scaling of the reference and oscillator frequencies are also used in the phase locked loop.

8. The frequency synthesizer of claim 6, wherein the oscillator is a voltage controlled oscillator, and wherein the phase locked loop includes a charge pump that generates input voltages for the voltage controlled oscillator after calibration based on a comparison of the signal indicative of the oscillator and the frequency indicative of a reference.

9. A frequency synthesizer comprising:

an oscillator including configurable circuitry that defines an initial frequency of the oscillator for an initial input parameter; and

means for adjusting the configurable circuitry based on a comparison of a signal indicative of the oscillator and a signal indicative of a reference, wherein the means for adjusting initializes the signals indicative of the oscillator and the reference so that the signals are substantially in phase.

10. The frequency synthesizer of claim 9, wherein the oscillator comprises a voltage controlled oscillator and the initial input parameter is an initial input voltage, and wherein the configurable circuitry comprises a number of switched capacitors, wherein the means for adjusting adjusts the configurable circuitry by activating a subset of the switched capacitors based on the comparison of the signal indicative of the oscillator and a signal indicative of the reference.

11. The frequency synthesizer of claim 10, further comprising means for generating the initial input voltage based on temperature.

12. The frequency synthesizer of claim 9, further comprising a first divider means that generates the signal indicative of the oscillator by scaling an oscillator frequency defined by the initial input parameter, and a second divider means that generates the signal indicative of the reference by scaling a reference frequency.

13. The frequency synthesizer of claim 12, wherein the means for adjusting initializes the signals indicative of the oscillator and the reference by initializing a divider circuit for initial frequency of the oscillator and a divider circuit for the reference frequency at approximately the same time.

14. The frequency synthesizer of claim 9, further comprising means for analog control of the oscillator following calibration.

15. The frequency synthesizer of claim 14, wherein the means for analog control and the oscillator are integrated as integrated circuitry.

16. The frequency synthesizer of claim 14, wherein the oscillator is a voltage controlled oscillator, and wherein the means for analog control includes a means for generating input voltages for the voltage controlled oscillator after calibration based on a comparison of the signal indicative of the oscillator and the signal indicative of a reference.

17. A method for calibrating a frequency synthesizer comprising:

comparing a signal indicative of an oscillator and a signal indicative of a reference;

adjusting configurable circuitry connected to the oscillator so that the signals are substantially in phase such an initial frequency of the oscillator is set for an initial input parameter.