Polar Amplification Transmitter Distortion Reduction

• US 20120264380A1
• Filed: 03/13/2012
• Published: 10/18/2012
• Est. Priority Date: 03/14/2011
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Nujira Limited (Qualcomm, Inc.)
• Inventors: Cobley, Kevin
• Granted Patent: US 9,344,041 B2
• Time in Patent Office: Days
• US Class Current: 455/77
• CPC Class Codes: H03F 1/0222 by using a signal derived from the input signal
• CPC Class Codes: H03F 1/32 Modifications of amplifiers to reduce non-linear distortion by negative feedback H03F1/34
• CPC Class Codes: H03F 2200/102 A non-specified detector of a signal envelope being used in an amplifying circuit
• CPC Class Codes: H03F 3/24 of transmitter output stages
• CPC Class Codes: H04L 27/361 Modulation using a single or unspecified number of carriers, e.g. with separate stages of phase and amplitude modulation
• CPC Class Codes: H04L 27/368 adaptive predistortion

Abstract

A method of optimising a transmitter, the transmitter including a polar amplification stage including a main signal path and a magnitude signal path, a receiver being located with the transmitter, the method comprising: generating an amplified signal for transmission at the output of the amplifier; tuning the receiver to a frequency to reject the intended transmit signal of the transmitter; determining a characteristic of a signal detected in the receiver representing an indication of distortion in the transmitted signal; and adjusting a setting of the transmitter in dependence on the determined characteristic.

Claims

1. A method of optimizing an envelope tracking transmitter, the envelope tracking transmitter including an envelope tracking amplification stage arranged to receive an input signal to be amplified and a power supply voltage tracking the envelope of the input signal to be amplified, a receiver being located with the transmitter, the method comprising:

generating an amplified signal for transmission at the output of the amplifier;

tuning the receiver to a frequency to reject the intended transmit signal of the transmitter;

determining a characteristic of a signal detected in the receiver representing an indication of distortion in the transmitted signal; and

adjusting a setting of the transmitter in dependence on the determined characteristic.

2. The method of claim 1 further comprising generating a signal for transmission by the transmitter, wherein the signal detected in the receiver comprises an intended received signal together with interference from the transmitter.

3. The method of claim 2 further comprising iteratively adjusting a setting of the transmitter over a plurality of values and determining a characteristic of a signal detected in the receiver for each value;

averaging the iterative results;

determining the value which optimizes performance, and selecting this value as the setting for the transmitter

4. The method of claim 1 wherein the step of determining a characteristic of a signal detected in the receiver comprises generating a quality of service indicator for the signal detected in the receiver, and the step of adjusting the setting of the transmitter comprises adjusting said setting in order to improve the generated quality of service indicator.

5. The method of claim 1 further comprising generating a calibration signal for transmission by the transmitter, wherein the signal detected in the receiver comprises interference from the transmitter.

6. The method of claim 5 further comprising adjusting a setting of the transmitter over a plurality of values, and determining a characteristic of a signal detected in the receiver for each value;

determining the value which optimises performance, and selecting this value as the setting for the transmitter.

7. The method of claim 4 wherein the step of generating a quality of service indicator comprises generating one of a received signal strength indicator;

a signal-to-noise plus interference ratio;

or a quality of service parameter dependent upon a signal-to-noise plus interference ratio.

8. The method of claim 1 wherein the step of adjusting a setting in the transmitter comprises adjusting one or more of a delay in the main signal path, or a delay in the magnitude signal path.

9. The method of claim 1 wherein the transmitter circuit further includes a shaping function for generating a supply voltage in dependence on the magnitude of the signal to be amplified, the step of adjusting a setting in the transmitter comprising adjusting a setting of the shaping function.

10. An apparatus comprising an envelope tracking transmitter including an envelope tracking amplification stage arranged to receive an input signal to be amplified and a power supply voltage tracking the envelope of the input signal to be amplified, the apparatus further comprising a receiver adapted to reject the intended transmit signal of the transmitter, and including means for determining a characteristic of a signal detected in the receiver representing an indication of distortion in the transmitted signal;

and a controller for adjusting a setting of the transmitter in dependence on the determined characteristic of the received signal.

11. The apparatus of claim 10 wherein the transmitter is adapted to generate a signal for transmission, wherein the controller is adapted to detect a signal comprising a received signal and interference arising from distortion of the transmitter.

12. The apparatus of claim 11 wherein the controller is adapted to iteratively adjust a setting of the transmitter over a plurality of values and determine a characteristic of a signal detected in the receiver for each value;

average the iterative results;

determine the value which optimizes performance, and select this value as the setting for the transmitter.

13. The apparatus of claim 10 wherein the controller is adapted to adjust the setting of the transmitter in order to reduce the distortion in the transmitted signal.

14. The apparatus of claim 10 wherein the receiver is adapted to generate a quality of service indicator for the signal detected in the receiver, and the controller is adapted to adjust the setting of the transmitter order to improve the quality of service indicator.

15. The apparatus of claim 10 further comprising a signal generator for generating a calibration signal for transmission by the transmitter, wherein the receiver is adapted to detect distortion from the transmitter.

16. The apparatus of claim 15 wherein the controller is adapted to adjust the setting of the transmitter for a plurality values, and the controller is further adapted to determine a characteristic of a signal detected in the receiver for each value;

the controller being adapted to determine the value which optimizes performance, and to select this value as the setting for the transmitter.

17. The apparatus of claim 10 wherein the step of generating a quality of service indicator comprises generating one of a received signal strength indicator;

a signal-to-noise plus interference ratio;

or a quality of service parameter dependent upon a signal-to-noise plus interference ratio.

18. The apparatus of claim 10 wherein the step of adjusting a setting in the transmitter comprises adjusting one or more of a delay in the main signal path, or a delay in the magnitude signal path.

19. The apparatus of claim 10 wherein the transmitter circuit further includes a shaping function for generating a supply voltage in dependence on the magnitude of the signal to be amplified, the step of adjusting a setting in the transmitter comprising adjusting a setting of the shaping function.

20. A transceiver including an apparatus according to claim 10, wherein the amplifier is a radio frequency, RF, amplifier, and the input path is an RF signal path.