Adaptively extending tunable range of frequency in a closed loop

• US 20040119547A1
• Filed: 12/19/2002
• Published: 06/24/2004
• Est. Priority Date: 12/19/2002
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Intel Corporation
• Inventors: Ravi, Ashoke, Banerjee, Gaurab, Soumyanath, Krishnamurthy
• Granted Patent: US 6,885,873 B2
• Time in Patent Office: Days
• US Class Current: 331/182
• CPC Class Codes: H03L 7/0898 the source or sink current values being variable H03L7/0896 takes precedence
• CPC Class Codes: H03L 7/093 using special filtering or amplification characteristics in the loop H03L7/087 - H03L7/091 take precedence
• CPC Class Codes: H03L 7/107 using a variable transfer function for the loop, e.g. low pass filter having a variable bandwidth
• CPC Class Codes: H03L 7/18 using a frequency divider or counter in the loop H03L7/20, H03L7/22 take precedence

Abstract

A semiconductor device or a circuit includes a controllable oscillator and circuitry that senses a voltage which may control the controllable oscillator and digitally controls a gain compensation, adaptively compensating for a drop in a gain against overall loop gain within a closed loop. In one embodiment, a single supply source may be used to power the closed loop while a variable gain stage that is digitally controllable may adjust the gain in a feed-forward manner based on the drop.

Claims

1. A method comprising:

sensing a signal that controls an oscillator to determine a drop in a gain against an overall loop gain within a closed loop; and

digitally controlling a variable gain stage to adaptively compensate the gain based on the drop while supplying power to the variable gain stage and said oscillator from a same supply source.

2. The method of claim 1, wherein digitally controlling including:

forming the closed loop in a wireless transceiver to communicate via a wireless network over a tunable range of frequency;

providing a gain compensation for the drop in the gain in a feed-forward manner; and

based on the gain compensation, extending the tunable range of frequency up to a full range of said oscillator.

3. The method of claim 1, wherein sensing the signal including:

monitoring a voltage that controls said oscillator; and

based on the monitoring, providing a gain compensation for the drop in the gain for said oscillator at two ends of an available range for the voltage.

4. The method of claim 1 further including measuring a control voltage controlling one or more tuning characteristics of said oscillator.

5. The method of claim 4 including correcting the drop in the gain at two ends of an available range for the control voltage by adaptively adjusting the overall loop gain of the control loop through the variable gain stage.

6. The method of claim 5 including:

monitoring at least one of said one or more tuning characteristics of said oscillator;

adjusting said at least one of said one or more tuning characteristics; and

providing a piece-wise linear compensation of the drop in the gain of said oscillator based on said adjusted at least one of said one or more tuning characteristics.

7. The method of claim 1 including maintaining for the closed loop at least one of a settling time, a phase-noise specification and an attenuation metric at a predetermined level.

8. The method of claim 7, wherein maintaining further including adapting the gain of said oscillator to extend the tunable range of frequency beyond a linear region of a frequency-voltage relationship for the closed loop.

9. The method of claim 4 including:

receiving a reference frequency from an external source; and

using a bias current source to control a gain drop-off at a charge pump which is deployed to form a phase-locked loop in the closed loop.

10. The method of claim 9, wherein using the bias current source including:

providing in the bias current source, a complementary structure of a first and a second transistor type;

based on the control voltage, scaling a source current in one portion of the complementary structure that includes the first transistor type and scaling a sink current in the other portion thereof that includes the second transistor type; and

mirroring said source and sink currents into the charge pump.

11. A device comprising:

a controllable oscillator; and

circuitry operably coupled to said controllable oscillator, said circuitry to sense a voltage that controls said controllable oscillator and to digitally control a gain compensation to adaptively compensate for a drop in a gain against an overall loop gain within a closed loop.

12. The device of claim 11, wherein said circuitry including:

a sensing logic that detects the drop in the gain of said controllable oscillator; and

a variable gain stage that is digitally controllable to adjust the gain based on the drop in a feed-forward manner responsive to said sensing logic.

13. The device of claim 11, wherein said interface comprising:

a charge pump to provide an input voltage to said circuitry to generate a control voltage for said controllable oscillator to extend a tunable range of frequency associated with the closed loop.

14. The device of claim 11, wherein the closed loop forms a phase-locked loop.

15. The device of claim 11, wherein the closed loop forms a frequency synthesizer.

16. The device of claim 13, wherein said semiconductor device is disposed in a wireless transceiver to communicate via a wireless network over the tunable range of frequency.

17. The device of claim 12, further comprising:

an interface to receive a reference frequency from a source external to said device;

a single supply source to power each of said interface, controllable oscillator, charge pump and circuitry; and

a bias current source to control a gain drop-off at said charge pump.

18. The device of claim 17, wherein said variable gain stage is being digitally controlled in a feed-forward manner responsive to said reference frequency and said single supply source.

19. The device of claim 18, wherein said bias current source including a complementary structure of a first and a second transistor type.

20. The device of claim 19, wherein said complementary structure including:

an N-type metal oxide semiconductor and a P-type metal oxide semiconductor stack to either source or sink currents based on the control voltage; and

an N-type metal oxide semiconductor and a P-type metal oxide semiconductor current mirror to mirror said source and sink currents into said charge pump.

21. An article comprising a medium storing instructions that, when executed result in:

sensing a signal that controls an oscillator to determine a drop in a gain against an overall loop gain within a closed loop; and

digitally controlling a variable gain stage to adaptively compensate the gain based on the drop while supplying power to the variable gain stage and said oscillator from a single supply source.

22. The article of claim 21, comprising a medium storing instructions that, when executed result in:

forming the closed loop in a wireless transceiver to communicate via a wireless network over a tunable range of frequency;

providing a gain compensation for the drop in the gain in a feed-forward manner; and

based on the gain compensation, extending the tunable range of frequency up to a full range of said oscillator.

23. The article of claim 21, comprising a medium storing instructions that, when executed result in:

monitoring a voltage that controls said oscillator; and

based on the monitoring, providing a gain compensation for the drop in the gain for said oscillator at two ends of an available range for the voltage.

24. The article of claim 21, comprising a medium storing instructions that, when executed result in measuring a control voltage controlling one or more tuning characteristics of said oscillator.

25. The article of claim 24, comprising a medium storing instructions that, when executed result in correcting the drop in the gain at two ends of an available range for the control voltage by adaptively adjusting the overall loop gain of the control loop through the variable gain stage.

26. The article of claim 25, comprising a medium storing instructions that, when executed result in:

monitoring at least one of said one or more tuning characteristics of said oscillator;

adjusting said at least one of said one or more tuning characteristics; and

providing a piece-wise linear compensation of the drop in the gain of said oscillator based on said adjusted at least one of said one or more tuning characteristics.

27. The article of claim 21, comprising a medium storing instructions that, when executed result in maintaining for the closed loop at least one of a settling time, a phase-noise specification and an attenuation metric at a predetermined level.

28. The article of claim 27, comprising a medium storing instructions that, when executed result in adapting the gain of said oscillator to extend the tunable range of frequency beyond a linear region of a frequency-voltage relationship for the closed loop.

29. The article of claim 24, comprising a medium storing instructions that, when executed result in:

receiving a reference frequency from an external source; and

using a bias current source to control a gain drop-off at a charge pump which is deployed to form a phase-locked loop in the closed loop.

30. The article of claim 29, comprising a medium storing instructions that, when executed result in:

providing in the bias current source, a complementary structure of a first and a second transistor type;

based on the control voltage, scaling a source current in one portion of the complementary structure that includes the first transistor type and scaling a sink current in the other portion thereof that includes the second transistor type; and

mirroring said source and sink currents into the charge pump.

31. A communication system comprising:

a wireless interface that communicates over a wireless local area network;

a controllable oscillator disposed in said wireless interface;

a device operably coupled to said controllable oscillator to extend a tunable range of frequency within a closed loop by adaptively compensating for a drop in a gain of said controllable oscillator against an overall loop gain in the closed loop; and

a radio frequency transceiver operably coupled to said device to receive and transmit a wireless communication via the wireless local area network within said tunable range of frequency.

32. The communication system of claim 31, wherein said wireless interface further comprising:

an interface to receive a reference frequency from a source external to said wireless interface; and

a supply source to power said wireless interface.

33. The communication system of claim 32, wherein said wireless interface further comprising:

a compensation circuit operably coupled between said interface and said controllable oscillator to form the closed loop, sense a voltage that controls said controllable oscillator and digitally control a gain compensation, said compensation circuit including;

a sensing logic that detects a voltage that controls said controllable oscillator and provides digital controls for a gain compensation; and

a variable gain stage coupled to said sensing logic to adaptively compensate for the drop in the gain based on the gain compensation.