Phase locked loop modulator calibration techniques

• US 7,538,623 B2
• Filed: 11/16/2005
• Issued: 05/26/2009
• Est. Priority Date: 09/08/2003
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Kim, Hea Joung, Jensen, Henrik T.
• Primary Examiner(s): MIS, DAVID C
• Application Number:
  US11/281,165
• Publication Number:
  US 20060077010A1
• Time in Patent Office: 1,287 Days
• Field of Search: 331/1.A, 331/14, 331 16- 18, 331/23, 331/25, 331/DIG.2, 327156-159, 332/127, 360/51, 375/376, 455/260
• US Class Current: 331/17
• CPC Class Codes: H03C 3/0991 including calibration means or calibration methods
• CPC Class Codes: H03L 7/0898 the source or sink current values being variable H03L7/0896 takes precedence

Abstract

A method for calibrating a phase locked loop begins by determining a gain offset of a voltage controlled oscillator of the phase locked loop. The processing then continues by adjusting current of a charge pump of the phase locked loop based on the gain offset.

Claims

1. A method for operating a translational loop, the method comprising:

in a calibration operation;

performing open loop calibration of a voltage controlled oscillator of the translational loop;

determining a gain offset of the voltage controlled oscillator of the translational loop; and

adjusting current of a charge pump of the translational loop based on the gain offset; and

in a transmit operation, using the translational loop to convert a modulated baseband signal to a Radio Frequency (RF) signal.

2. The method of claim 1, wherein determining the gain offset further comprises:

measuring a control voltage of the voltage controlled oscillator when a reference oscillation is input to the translational loop to produce a first measured control voltage;

injecting a frequency offset into the translational loop;

measuring the control voltage of the voltage controlled oscillator to produce a second measured control voltage; and

determining the gain offset based on the frequency offset, the first measured control voltage, and the second measured control voltage.

3. The method of claim 2, further comprising waiting for expiration of a settling period after injecting the frequency offset before measuring the control voltage.

4. The method of claim 2, further comprising:

injecting a second frequency offset into the translational loop;

measuring the control voltage of the voltage controlled oscillator to produce a third measured control voltage; and

determining the gain offset based on the frequency offset, the second frequency offset, the first measured control voltage, the second measured control voltage, and the third measured control voltage.

5. The method of claim 4, further comprising waiting for expiration of a settling period after injecting the second frequency offset before measuring the control voltage.

6. The method of claim 1, wherein adjusting current of the charge pump further comprises:

converting the gain offset to a digital value;

interpreting the digital value to determine a current adjust value; and

adjusting input to at least one dependent current source of the charge pump based on the current adjust value.

7. The method of claim 1, further comprising:

receiving an RF signal; and

converting the received RF signal to a modulated baseband signal.

8. The method of claim 1, wherein the modulated baseband signal is modulated in one of:

a frequency shift keying format;

a phase shift keying format; and

a magnitude shift keying format.

9. An auto-calibrating translational loop comprising:

a phase and frequency detection module operably coupled;

to produce an up signal when at least one of phase and frequency of a modulated baseband signal leads at least one of phase and frequency of a feedback oscillation; and

to produce a down signal when the at least one of phase and frequency of the feedback signal leads the at least one of phase and frequency of the modulated baseband signal;

a charge pump circuit operably coupled to convert the up signal and down signal into a current signal;

a loop filter operably coupled to convert the current signal into a control voltage;

a voltage controlled oscillator operably coupled to convert the control voltage into a Radio Frequency (RF) signal, wherein the feedback oscillation is derived from the RF signal; and

a calibration module operably coupled to;

perform an open loop calibration of the voltage controlled oscillator;

determine a gain offset of the voltage controlled oscillator; and

adjust at least one current source of the charge pump based on the gain offset.

10. The auto-calibrating translational loop of claim 9, wherein the calibration module is operable to determine the gain offset by:

measuring a control voltage of the voltage controlled oscillator when a reference oscillation is inputted to the translational loop to produce a first measured control voltage;

injecting a frequency offset into the translational loop;

measuring the control voltage of the voltage controlled oscillator to produce a second measured control voltage; and

determining the gain offset based on the frequency offset, the first measured control voltage and the second measured control voltage.

11. The auto-calibrating translational loop of claim 10, wherein the calibration module waits for expiration of a settling period after injecting the frequency offset before measuring the control voltage.

12. The auto-calibrating translational loop of claim 10, wherein the calibration module is further operable to:

inject a second frequency offset into the translational loop;

measure the control voltage of the voltage controlled oscillator to produce a third measured control voltage; and

determine the gain offset based on the frequency offset, the second frequency offset, the first measured control voltage, the second measured control voltage, and the third measured control voltage.

13. The auto-calibrating translational loop of claim 12, wherein the calibration module waits for expiration of a settling period after injecting the second frequency offset before measuring the control voltage.

14. The auto-calibrating translational loop of claim 9, wherein the modulated baseband signal comprises at least one of:

a frequency shift keying modulated signal;

a phase shift keying modulated signal; and

a magnitude shift keying modulated signal.

15. A radio transceiver comprising:

a translational loop comprising;

a phase and frequency detection module operably coupled;

to produce an up signal when at least one of phase and frequency of a modulated baseband signal leads at least one of phase and frequency of a feedback oscillation; and

to produce a down signal when the at least one of phase and frequency of the feedback oscillation leads the at least one of phase and frequency of the modulated baseband signal;

a charge pump circuit operably coupled to convert the up signal and down signal into a current signal;

a loop filter operably coupled to convert the current signal into a control voltage;

a voltage controlled oscillator operably coupled to convert the control voltage into a Radio Frequency (RF) signal, wherein the feedback oscillation is derived from the RF signal; and

a calibration module operably coupled to;

perform an open loop calibration of the voltage controlled oscillator to produce an open loop calibrated voltage controlled oscillator;

determine a gain offset of the open loop calibrated voltage controlled oscillator; and

adjust at least one current source of the charge pump based on the gain offset; and

a receiver section operable to receive an RF signal and convert the received RF signal into a received modulated baseband signal.

16. The radio transceiver of claim 15, wherein the calibration module further functions to determine the gain offset by:

measuring a control voltage of the voltage controlled oscillator when a reference oscillation is inputted to the translational loop to produce a first measured control voltage;

injecting a frequency offset into the translational loop;

measuring the control voltage of the voltage controlled oscillator to produce a second measured control voltage; and

determining the gain offset based on the frequency offset, the first measured control voltage and the second measured control voltage.

17. The radio transceiver of claim 16, wherein the calibration module further functions to wait for expiration of a settling period after injecting the frequency offset before measuring the control voltage.

18. The radio transceiver of claim 16, wherein the calibration module further functions to:

inject a second frequency offset into the translational loop;

measure the control voltage of the voltage controlled oscillator to produce a third measured control voltage; and

determine the gain offset based on the frequency offset, the second frequency offset, the first measured control voltage, the second measured control voltage, and the third measured control voltage.

19. The radio transceiver of claim 18, wherein the calibration module further functions to wait for expiration of a settling period after injecting the second frequency offset before measuring the control voltage.

20. The radio transceiver of claim 15, wherein the modulated baseband signal comprises at least one of:

a frequency shift keying modulated signal;

a phase shift keying modulated signal; and

a magnitude shift keying modulated signal.