Power control feedback loop for adjusting a magnitude of an output signal

• US 20070206523A1
• Filed: 09/30/2005
• Published: 09/06/2007
• Est. Priority Date: 09/30/2005
• Status: Active Grant

• Current Assignee: North Star Innovations Inc. (Wi-LAN Inc.)
• Original Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Inventors: Sharma, Nitin, Huynh, Phuong
• Granted Patent: US 7,558,539 B2
• Time in Patent Office: Days
• US Class Current: 370/318
• CPC Class Codes: H03G 3/001 Digital control of analog signals
• CPC Class Codes: H03G 3/3042 in modulators, frequency-changers, transmitters or power amplifiers transmission power control in bidirectional transmission systems H04W52/04

Abstract

A circuit for adjusting a magnitude of a transmit signal includes a transmitter (105), providing a transmit signal (107). It also includes a transmitter amplifier (109), receiving the transmit signal (107) and a power control adjustment signal (121), and responsive thereto, providing an amplified transmit signal (111). The circuit also includes a detector (1 23), for detecting an amplitude of the amplified transmit signal (111). Also included is an error component (137) for determining the difference between the amplitude and a reference level (129). Further provided is a digital signal generator (155), receiving the difference (145), and responsive thereto, generating (157) a reference signal (125) and the power control adjustment signal (117, 121), where the reference level (129) is responsive to the reference signal (125).

Claims

1. A circuit for adjusting a magnitude of a transmit signal, comprising:

a transmitter, providing a transmit signal;

an amplifier, receiving the transmit signal and a power control adjustment signal, and responsive thereto, providing an amplified transmit signal;

a detector, for detecting an amplitude of the amplified transmit signal;

an error component for determining the difference between the amplitude and a reference level; and

a digital signal generator, receiving the difference, and responsive thereto, generating a reference signal and the power control adjustment signal;

wherein the reference level is responsive to the reference signal.

2. The circuit of claim 1, wherein the digital signal generator comprises

an analog to digital circuit receiving the difference and generating a digital difference signal representative of the difference;

and

a processor configured to facilitate receiving the digital difference signal, processing the difference, and adjusting the reference signal and the power control signal responsive to the difference.

3. The circuit of claim 2, wherein the analog to digital circuit is an n-bit analog to digital circuit, where n is two or more.

4. The circuit of claim 1, wherein the difference is a signal provided by the error component, further comprising a multiplexer, multiplexing between a receive signal from a receiver corresponding to the transmitter, and the difference, to provide the difference and the receive signal to the digital signal generator.

5. The circuit of claim 4, wherein the multiplexer selects between the receive signal and the difference responsive to the digital signal generator.

6. The circuit of claim 1, further comprising

a first digital to analog converter, for converting the reference signal from digital to analog;

a second digital to analog converter, for converting the power control adjustment signal from digital to analog; and

a radio frequency control block, receiving the reference signal and the power control adjustment signal, and translating the reference signal and the power control adjustment signal to values for the first digital to analog converter and the second digital to analog converter.

7. The circuit of claim 1, wherein there are a plurality of the reference levels including the reference level, the reference levels being pre-determined.

8. The circuit of claim 1, wherein the detector is configured to track out variations in at least one of a temperature, a process corner and a common-mode voltage.

9. A method for determining transmit power in a signal, comprising:

detecting peaks in a transmit signal;

detecting an error from at least one error source affecting the transmit signal, relative to a reference level;

detecting a deviation in the error from an error level; and

correcting a transmitted output level for the error.

10. The method of claim 9, wherein the at least one error source is at least one of temperature variation and process corner variation.

11. The method of claim 9, wherein the at least one error source is common mode voltage, wherein the detecting further comprises obtaining a difference between the actual peak voltage and the common mode voltage.

12. The method of claim 9, wherein the at least one error source is a resistor, wherein a DAC current is proportional to the tolerance of the resistor.

13. The method of claim 9, wherein the transmit signal is single ended.

14. The method of claim 9, wherein the transmit signal is differential.

15. A method of adjusting a magnitude of a transmit signal, comprising:

receiving a transmit signal;

generating a digital error signal, responsive to the transmit signal, wherein the digital error signal represents a difference between an amplitude of the transmit signal and a reference level;

providing a transmit power control, responsive to the digital error signal; and

adjusting the transmit signal, responsive to the transmit power control.

16. The method of claim 15, further comprising receiving a reference signal, the reference signal being digital, converting the reference signal from digital to analog, and generating the reference level responsive to the analog reference signal.

17. The method of claim 15, wherein the adjusting further comprises receiving a digital indication of an adjustment, and adjusting a gain of an amplifier providing the transmit power control, responsive to the adjustment.

18. The method of claim 17, further comprising converting the adjustment from digital to analog, wherein the gain is adjusted responsive to the analog adjustment.

19. The method of claim 15, further comprising determining the transmit power control.

20. The method of claim 15, further periodically sampling the digital error signal, wherein the transmit power control can be altered responsive to the sampled digital error signal.