Reducing power amplifier gain drift during a data burst

Patent metadata

Field	Value
Publication number	US-2017194916-A1
Application number	US-201615390928-A
Country	US
Kind code	A1
Filing date	Dec 27, 2016
Priority date	Dec 30, 2015
Publication date	Jul 6, 2017
Grant date	—

Abstract

A bias circuit provides additional bias current for power amplifiers during data bursts to compensate for the gain droop caused by a rise in the power amplifier temperature during the data burst. A bias circuit includes a difference amplifier and switches coupled to the difference amplifier. The switches operate the bias circuit in a first mode when a transmit data burst is detected and operate the bias circuit in a second mode after the bias circuit has operated in the first mode for a predetermined period of time. In the first mode, the bias circuit charges a storage capacitor and sets an output current to zero. In the second mode, the bias circuit outputs the output current that increases above the initial value of zero as the PA warms up, where the excursion of this increase of current is determined by a register. The switches disable the bias circuit when the transmit data burst ends.

First claim

What is claimed is:

1 . A power amplifier system comprising:
a power amplifier configured to amplify a radio frequency signal that includes a transmit data burst; a temperature sensor configured to provide an indication of temperature of the power amplifier; and a bias circuit configured to detect a change in the temperature of the power amplifier based on the indication of the temperature during the transmit data burst, the bias circuit further configured to generate a bias compensation signal based on an indication of the change in the temperature of the power amplifier and a temperature coefficient.

2 . The power amplifier system of claim 1 wherein the bias compensation signal causes a gain of the power amplifier to be adjusted.

3 . The power amplifier system of claim 1 wherein the bias circuit includes a sampling circuit configured to charge a storage capacitor for a period of time when the transmit data burst is detected and to provide the indication of the change in the temperature of the power amplifier when the period of time has elapsed.

4 . The power amplifier system of claim 1 wherein the bias circuit includes a coefficient register configured to provide the temperature coefficient and a scaling circuit configured to multiply the indication of the change in the temperature of the power amplifier by the temperature coefficient to generate the bias compensation signal.

5 . The power amplifier system of claim 1 wherein the transmit data burst is less than 1 millisecond.

6 . The power amplifier system of claim 1 wherein the transmit data burst is between and including 1 millisecond and 5 milliseconds.

7 . The power amplifier system of claim 1 wherein the transmit data burst is greater than 5 milliseconds.

8 . The power amplifier system of claim 1 wherein an output current of the bias circuit increases as the temperature of the power amplifier increases during the transmit data burst.

9 . The power amplifier system of claim 1 wherein the power amplifier and the temperature sensor are implemented on a gallium arsenide die and the bias circuit is implemented on a complementary metal-oxide semiconductor die.

10 . The power amplifier system of claim 1 wherein the power amplifier system is configured to operate within a wireless local area network.

11 . A method of adjusting a gain of a power amplifier, the method comprising:
detecting a transmit data burst; measuring a temperature of the power amplifier during the transmit data burst; providing an indication of a change in the temperature of the power amplifier during the transmit data burst; generating a bias compensation signal based on the indication of the change in the temperature of the power amplifier and a temperature coefficient; and adjusting the gain of the power amplifier based on the bias compensation signal.

12 . The method of claim 11 further comprising sampling an indication of the temperature of the power amplifier for a first time interval after the transmit data burst is detected.

13 . The method of claim 12 further comprising providing the indication of the change in the temperature of the power amplifier during a second time interval of the transmit data burst that begins after the first time interval has ended.

14 . The method of claim 11 further comprising multiplying the indication of the change in the temperature of the power amplifier by the temperature coefficient.

15 . The method of claim 11 further comprising disabling circuitry generating the bias compensation signal when the transmit data burst has ended.

16 . A wireless communication device comprising:
a power amplifier configured to provide an amplified radio frequency signal; an antenna configured to transmit the amplified radio frequency signal; a temperature sensor configured to provide an indication of a temperature of the power amplifier; and a bias circuit configured to generate a bias signal to compensate for a change in a gain of the power amplifier during a transmit data burst by detecting a change in the temperature of the power amplifier based on the indication of temperature during the transmit data burst and multiplying an indication of the change in the temperature by a temperature coefficient.

17 . The wireless communication device of claim 16 wherein the bias circuit includes a sampling circuit configured to sample the indication of the temperature of the power amplifier for a first time interval after the transmit data burst is detected and to provide an indication of the change in the temperature of the power amplifier during a second time interval of the transmit data burst that begins after the first time interval has ended.

18 . The wireless communication device of claim 16 wherein the bias circuit includes a register configured to provide the temperature coefficient and a scaling circuit configured to multiply the indication of the change in the temperature of the power amplifier by the temperature coefficient.

19 . The wireless communication device of claim 16 wherein the transmit data burst is between and including 1 millisecond and 5 milliseconds.

20 . The wireless communication device of claim 16 configured as a mobile phone.

Assignees

• Skyworks Solutions Inc

Inventors

• Whittaker Edward John Wemyss
• Rabjohn Gordon Glen

Classifications

• H03F1/56

  Modifications of input or output impedances, not otherwise provided for · CPC title

• H03F3/245

  with semiconductor devices only · CPC title

• H03F2200/27

  A biasing circuit node being switched in an amplifier circuit · CPC title

• H03F2200/447

  the amplifier being protected to temperature influence · CPC title

• H03F2200/387

  A circuit being added at the output of an amplifier to adapt the output impedance of the amplifier · CPC title