Apparatus and methods for phase compensation in power amplifiers

Patent metadata

Field	Value
Publication number	US-9455669-B2
Application number	US-201414509344-A
Country	US
Kind code	B2
Filing date	Oct 8, 2014
Priority date	Oct 11, 2013
Publication date	Sep 27, 2016
Grant date	Sep 27, 2016

Abstract

Apparatus and methods for phase compensation in power amplifiers are disclosed herein. In certain implementations, a power amplifier includes an input stage, an output stage, an envelope tracker, and a compensation circuit. The input and output stages are cascaded and amplify an input RF signal to generate an amplified output RF signal. The envelope tracker generates a power amplifier supply voltage for at least the output stage based on an envelope of the input RF signal. The compensation circuit compensates for changes in input impedance of the output stage associated with changes in the voltage level of the power amplifier supply voltage. By including the compensation circuit, a variation in the power amplifier's phase delay versus input power can be reduced, thereby leading to an improvement in the power amplifier's phase distortion (AM/PM).

First claim

What is claimed is:

1. A method of phase compensation in a power amplifier system, the method comprising:
amplifying an input radio frequency (RF) signal to generate a first amplified RF signal using a first amplification stage of a power amplifier;
generating a power amplifier supply voltage using an envelope tracker;
controlling a voltage level of the power amplifier supply voltage based on an envelope of the input RF signal using the envelope tracker;
powering a second amplification stage of the power amplifier using the power amplifier supply voltage from the envelope tracker;
amplifying the first amplified RF signal to generate a second amplified signal using the second amplification stage, amplifying the first amplified RF signal to generate the second amplified signal including receiving the first amplified RF signal at a base of a bipolar transistor and generating the second amplified RF signal at a collector of the bipolar transistor; and
compensating for a variation in an input impedance of the second amplification stage associated with changes in the voltage level of the power amplifier supply voltage using a compensation circuit.

2. The method of claim 1 further comprising providing a matching impedance between the first and second amplification stages that is in the range of about 60Ω to about 70Ω using the compensation circuit.

3. The method of claim 1 , further comprising compensating for a variation in a parasitic capacitance between the base and the collector of the bipolar transistor associated with changes in the voltage level of the power amplifier supply voltage using the compensation circuit.

4. The method of claim 1 further comprising generating the RF signal and the envelope of the RF signal using a transceiver.

5. A power amplifier system comprising:
a first power amplifier stage including an input configured to receive an input radio frequency (RF) signal and an output configured to generate a first amplified RF signal;
an envelope tracker configured to generate a power amplifier supply voltage and to control a voltage level of the power amplifier supply voltage based on an envelope of the input RF signal;
a second power amplifier stage including an input configured to receive the first amplified RF signal and an output configured to generate a second amplified RF signal, the second power amplifier stage configured to be powered by the power amplifier supply voltage from the envelope tracker, the second power amplifier stage further including a bipolar transistor including a base configured to receive the first amplified RF signal and a collector configured to generate the second amplified RF signal; and
a compensation circuit electrically connected between the output of the first power amplifier stage and the input of the second power amplifier stage, the compensation circuit configured to compensate for variation in input impedance of the second power amplifier stage associated with changes in the voltage level of the power amplifier supply voltage.

6. The power amplifier system of claim 5 wherein the compensation circuit is configured to provide a matching impedance between the first and second power amplifier stages that is in the range of about 60Ω to about 70Ω.

7. The power amplifier system of claim 5 wherein the compensation circuit is configured to compensate for a variation in a parasitic capacitance between the base and the collector of the bipolar transistor associated with changes in the voltage level of the power amplifier supply voltage.

8. The power amplifier system of claim 5 wherein the compensation circuit includes a first compensation capacitor electrically connected between the input of the second power amplifier stage and an output of the first power amplifier stage.

9. The power amplifier system of claim 8 wherein the compensation circuit further includes a first compensation inductor electrically connected between the output of the first power amplifier stage and an input stage power supply.

10. A power amplifier system comprising:
a first power amplifier stage including an input configured to receive an input radio frequency (RF) signal and an output configured to generate a first amplified RF signal;
an envelope tracker configured to generate a power amplifier supply voltage and to control a voltage level of the power amplifier supply voltage based on an envelope of the input RF signal;
a second power amplifier stage including an input configured to receive the first amplified RF signal and an output configured to generate a second amplified RF signal, the second power amplifier stage configured to be powered by the power amplifier supply voltage from the envelope tracker; and
a compensation circuit electrically connected between the output of the first power amplifier stage and the input of the second power amplifier stage, the compensation circuit configured to compensate for variation in input impedance of the second power amplifier stage associated with changes in the voltage level of the power amplifier supply voltage, the compensation circuit including a first compensation capacitor electrically connected between the input of the second power amplifier stage and an output of the first power amplifier stage, a first compensation inductor electrically connected between the output of the first power amplifier stage and an input stage power supply, and a second compensation inductor electrically connected between the first compensation inductor and the input stage power supply, the first and second compensation inductors electrically connected at a first node.

11. The power amplifier system of claim 10 wherein the compensation circuit further includes a third compensation inductor and a second compensation capacitor electrically connected in series between the first node and a power low supply.

12. A power amplifier system comprising:
a first power amplifier stage including an input configured to receive an input radio frequency (RF) signal and an output configured to generate a first amplified RF signal;
an envelope tracker configured to generate a power amplifier supply voltage and to control a voltage level of the power amplifier supply voltage based on an envelope of the input RF signal;
a second power amplifier stage including an input configured to receive the first amplified RF signal and an output configured to generate a second amplified RF signal, the second power amplifier stage configured to be powered by the power amplifier supply voltage from the envelope tracker;
a compensation circuit electrically connected between the output of the first power amplifier stage and the input of the second power amplifier stage, the compensation circuit configured to compensate for variation in input impedance of the second power amplifier stage associated with changes in the voltage level of the power amplifier supply voltage, the compensation circuit including a first compensation capacitor electrically connected between the input of the second power amplifier stage and an output of the first power amplifier stage, and a first compensation inductor electrically connected between the output of the first power amplifier stage and an input stage power supply, and
an output stage bias current generation circuit configured to provide a bias current to the input of the second power amplifier stage.

13. The power amplifier system of claim 12 wherein the compensation circuit further includes a bias inductor configured to provide the bias current from the output stage bias current generation circuit to the input of the second power amplifier stage, the bias inductor configured to provide a portion o

Assignees

• Skyworks Solutions Inc

Inventors

• Modi Hardik Bhupendra
• Khesbak Sabah
• Zhang Guohao

Classifications

• H03F2203/21193

  the supply voltage of a power amplifier being continuously controlled, e.g. by an active potentiometer · CPC title

• H03F2200/451

  the amplifier being a radio frequency amplifier · CPC title

• H03F2200/504

  the supply voltage or current being continuously controlled by a controlling signal, e.g. the controlling signal of a transistor implemented as variable resistor in a supply path for, an IC-block showed amplifier · CPC title

• H03F2200/102

  A non-specified detector of a signal envelope being used in an amplifying circuit · CPC title

• H03F1/0222 Primary

  by using a signal derived from the input signal · CPC title