RF TRANSCEIVER FRONT END MODULE WITH IMPROVED LINEARITY

• US 20150333781A1
• Filed: 05/18/2015
• Published: 11/19/2015
• Est. Priority Date: 05/19/2014
• Status: Active Grant

• Current Assignee: Skyworks Solutions Incorporated
• Original Assignee: Skyworks Solutions Incorporated
• Inventors: Alon, Ziv, Thomas, Maxwell L.
• Granted Patent: US 10,333,474 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H03F 1/0227 using supply converters
• CPC Class Codes: H03F 1/3247 using feedback acting on predistortion circuits H03F1/3264 takes precedence
• CPC Class Codes: H03F 2200/451 the amplifier being a radio frequency amplifier
• CPC Class Codes: H03F 2201/3224 Predistortion being done for compensating memory effects
• CPC Class Codes: H03F 3/19 with semiconductor devices only
• CPC Class Codes: H03F 3/21 with semiconductor devices only H03F3/245 takes precedence
• CPC Class Codes: H03F 3/245 with semiconductor devices only
• CPC Class Codes: H04B 1/0475 with means for limiting noise, interference or distortion H04B1/0483 takes precedence
• CPC Class Codes: H04B 1/30 for homodyne or synchrodyne receivers demodulator circuits H03D1/22
• CPC Class Codes: H04B 2001/0425 with linearisation using predistortion
• CPC Class Codes: H04B 2001/0433 with linearisation using feedback
• CPC Class Codes: H04W 88/02 Terminal devices

Abstract

A power amplifier system front end measures both forward and reverse power associated with an RF transmit signal. A processor is configured to use measurements derived from the measured forward and reverse power output to adjust the RF transmit signal in order to compensate for one or more memory effects of the power amplifier system.

Claims

1. A power amplifier system comprising:

a modulator configured to generate a radio frequency (RF) transmit signal;

a front end module including a power amplifier configured to amplify the RF transmit signal to generate an amplified RF transmit signal and a coupler positioned between an antenna and the power amplifier, the coupler configured to output a measure of both forward and reverse power associated with the RF transmit signal;

non-volatile memory storing an equalizer table having a plurality of entries generated during a pre-characterization of the front-end module; and

a processor configured to (a) receive voltage standing wave ratio (VSWR) measurements derived from the forward and reverse power output by the coupler, (b) access entries in the equalizer table based at least in part on the VSWR measurements, and (c) adjust the RF transmit signal based on the accessed entries to compensate for one or more memory effects present in the power amplifier system.

2. The power amplifier system of claim 1 wherein the equalizer table was generated using a programmable antenna tuner to tune the front end module to desired VSWR points.

3. The power amplifier system of claim 1 wherein the front end module does not include an integrated antenna tuner.

4. The power amplifier system of claim 1 wherein the front end module further includes a programmable antenna tuner positioned between the antenna and the coupler.

5. The power amplifier system of claim 1 wherein the front end module further includes one or more duplexers positioned between the power amplifier and the dual directional coupler and which contribute to at least some of the memory effects.

6. The power amplifier system of claim 5 wherein the programmable antenna tuner is adjustable to tune an impedance seen by the power amplifier in order to provide a coarse correction of non-linearity within the power amplifier system, and the adjustment of the RF transmit signal based on the accessed entries provides fine correction of non-linearity within the power amplifier system.

7. The power amplifier system of claim 1 wherein the coupler is a dual directional coupler.

8. The power amplifier system of claim 1 further comprising a digital pre-distortion (DPD) table, the processor being configured to adjust the RF transmit signal by adapting values in the DPD table based on the accessed entries in the equalizer table.

9. The power amplifier system of claim 1 further comprising an envelope tracking system configured to provide a power supply control signal to the power amplifier to control a voltage level of the power amplifier based on a shaped envelope signal, the processor further configured to adjust a delay between the RF transmit signal and the supply control signal based on delay values included in the accessed equalizer table entries.

10. A method of characterizing a front end module of a wireless device, comprising:

using a programmable antenna tuner to tune an impedance load at an output of a power amplifier of the front end module so as to achieve a voltage standing wave ratio (VSWR) value associated with a first characterization state of a plurality of front end module characterization states;

driving the front end module with an RF transmit signal, the RF transmit signal driven according to one or more additional parameter values associated with the first characterization state;

measuring one or more variables associated with behavior of the front end module while the front end module is driven with the RF transmit signal and tuned to the VSWR values; and

recording the one or more measured variables in association with the first characterization state in a table in non-volatile memory.

11. The method of claim 10 further comprising repeating said steps of using, driving, measuring, and recording for a plurality of additional characterization states of the plurality of front end module characterization states.

12. The method of claim 10 wherein the programmable antenna tuner is separate from the front end module, and the front end module does not include an antenna tuner.

13. The method of claim 10 wherein the programmable antenna tuner is integrated into the front end module.

14. The method of claim 10 wherein the one or more recorded variables include a power amplifier compression.

15. The method of claim 10 wherein the one or more recorded variables include a maximum envelope power.

16. The method of claim 10 wherein the one or more recorded variables include a delay between a power control signal for the power amplifier and the RF transmit signal.

17. A mobile device comprising:

a modulator configured to generate a radio frequency (RF) transmit signal;

a front end module including a power amplifier configured to amplify the RF transmit signal to generate an amplified RF signal and a coupler configured to receive the amplified signal, the power amplifier configured to receive a power amplifier supply voltage for powering the power amplifier, the coupler configured to output a measure of both forward and reverse power associated with the RF transmit signal;

an antenna configured to receive the amplified RF signal from the front end module;

non-volatile memory storing an equalizer table having a plurality of entries generated during a pre-characterization of the front-end module; and

a processor configured to (a) receive voltage standing wave ratio (VSWR) measurements derived from the forward and reverse power output by the coupler;

(b) access entries in the equalizer table based at least in part on the VSWR measurements; and

(c) adjust the RF transmit signal based on the accessed entries to compensate for one or more memory effects present in the power amplifier system.

18. The mobile device of claim 17 wherein the front end module further includes one or more duplexers which contributes to at least some of the one or more memory effects.

19. A power amplifier system comprising:

a front end module including a power amplifier configured to amplify an RF transmit signal to generate an amplified RF transmit signal, a programmable antenna tuner coupled to an antenna, and a coupler positioned between the power amplifier and the antenna tuner, the coupler configured to output a measure of both forward and reverse power associated with the RF signal, the antenna tuner adjustable to tune an impedance seen by the power amplifier in order to provide a coarse correction of non-linearity within the power amplifier system;

non-volatile memory storing an equalizer table having a plurality of entries generated during a pre-characterization of the front-end module; and

a processor configured to (a) receive voltage standing wave ratio (VSWR) measurements derived from the forward and reverse power output by the coupler, (b) access entries in the equalizer table based at least in part on the VSWR, and (c) adjust the RF transmit signal based on the accessed entries.

20. The power amplifier system of claim 19 wherein the front end module further includes a duplexer.