Phase-locked loop based controller for adjusting an adaptive continuous-time filter

• US 7,869,780 B2
• Filed: 04/19/2007
• Issued: 01/11/2011
• Est. Priority Date: 04/19/2007
• Status: Active Grant

• Current Assignee: Skyworks Solutions Incorporated
• Original Assignee: Skyworks Solutions Incorporated
• Inventors: Youssoufian, Edward, Yates, David, Ismail, Aly M., Hatcher, Geoffrey
• Primary Examiner(s): Mendez, Manuel A
• Application Number:
  US11/737,426
• Publication Number:
  US 20080258806A1
• Time in Patent Office: 1,363 Days
• Field of Search: 455/222, 455/220, 340/310.12
• US Class Current: 455/222
• CPC Class Codes: H03H 11/1291 Current or voltage controlled filters
• CPC Class Codes: H03H 21/0012 Digital adaptive filters
• CPC Class Codes: H03H 2210/021 Amplifier, e.g. transconductance amplifier
• CPC Class Codes: H03H 2210/025 Capacitor
• CPC Class Codes: H03H 2210/028 Resistor
• CPC Class Codes: H03H 2210/036 Stepwise
• CPC Class Codes: H03H 2210/043 by measuring time constant
• CPC Class Codes: H03J 2200/10 Tuning of a resonator by means of digitally controlled capacitor bank

Abstract

A direct conversion radio-frequency (RF) receiver includes a controller and an adaptive continuous-time filter. The adaptive continuous-time filter receives a multiple-bit control signal generated by the controller to adjust a characteristic of the continuous-time filter. The controller generates the multiple-bit control signal in response to process variation in the semiconductor material used to implement the controller and the adaptive continuous-time filter. A method for tuning an adaptive continuous-time filter comprises determining a RC time constant, converting the RC time constant to a digital word, comparing a select bit of the digital word to a respective bit of a predetermined reference word to generate a control bit, applying the control bit to an adjustable element to modify the RC time constant, repeating the determining, converting, comparing and applying steps until the control bits generate an output word and providing the output word to the adaptive continuous-time filter.

Claims

1. A direct conversion radio-frequency (RF) receiver, comprising:

a controller including a RC time constant replicator using an array of elements, a digital phase-locked loop responsive to a system clock, and an oscillator configured to generate a signal having a frequency responsive to a RC time constant; and

a word generator configured to receive a multiple-bit control signal generated by the controller, the multiple-bit control signal responsive to process variation in the semiconductor material used to implement the controller and the RC time constant replicator.

2. The receiver of claim 1, wherein the controller is responsive to both the system clock and an enable signal.

3. The receiver of claim 2, wherein the controller is responsive to a reference word.

4. The receiver of claim 1, wherein the controller comprises a comparator configured to compare a digital representation of the RC time constant with a reference word to generate a difference signal.

5. The receiver of claim 4, wherein the controller comprises a set of successive approximation registers configured to receive the difference signal and a first output of the digital phase-locked loop and generate an output word.

6. The receiver of claim 5, wherein the controller comprises a first array of elements responsive to the output word.

7. The receiver of claim 6, wherein the first array of elements comprises capacitors.

8. The transceiver of claim 6, wherein the first array of elements comprises resistors.

9. The transceiver of claim 6, wherein the adaptive continuous-time filter comprises a second array of elements configured to duplicate the first array of elements.

10. A method for tuning an adaptive continuous-time filter, comprising:

determining a RC time constant;

converting the RC time constant to a digital word;

comparing a select bit of the digital word to a respective bit of a predetermined reference word to generate a control bit;

applying the control bit to an adjustable element to modify the RC time constant;

repeating the determining, converting, comparing and applying steps until the control bits generate an output word of a desired number of bits; and

providing the output word to an adaptive continuous-time filter.

11. The method of claim 10, wherein determining a RC time constant comprises using an oscillator responsive to a ratio of resistances.

12. The method of claim 10, wherein determining a RC time constant comprises using an astable multivibrator.

13. The method of claim 10, wherein converting the RC time constant to a digital word comprises applying a reference clock to a phase-locked loop.

14. The method of claim 13, wherein converting the RC time constant to a digital word comprises gating an output of an oscillator and an output of the phase-locked loop.

15. The method of claim 10, wherein applying the control bit comprises controllably inserting a capacitor into a feedback path.

16. The method of claim 15, wherein the capacitor has a capacitance commensurate with a respective weight of the control bit in the output word.

17. The method of claim 10, wherein applying the control bit comprises controllably bypassing a resistor in a feedback path.

18. The method of claim 17, wherein the resistor has a resistance commensurate with a respective weight of the control bit in the output word.