Saturation correction without using saturation detection and saturation prevention for a power amplifier

• US 8,874,050 B1
• Filed: 05/05/2010
• Issued: 10/28/2014
• Est. Priority Date: 05/05/2009
• Status: Active Grant

• Current Assignee: Qorvo US, Inc. (Qorvo, Inc.)
• Original Assignee: RF Micro Devices Incorporated (Qorvo, Inc.)
• Inventors: Hietala, Alexander Wayne, Ortiz, Jeffery Peter, Coffman, Timothy Keith
• Primary Examiner(s): Chen, Junpeng
• Application Number:
  US12/774,155
• Time in Patent Office: 1,637 Days
• Field of Search: 455/296, 455/127.1, 455/127.2, 4551141-1153, 455/115.1, 455/126, 455/114.3, 375/219, 375/320, 375/296, 375/297, 330/129, 330278-282, 330/254, 330/256, 330/260
• US Class Current: 455/127.1
• CPC Class Codes: H01P 5/184 the guides being strip lines or microstrips
• CPC Class Codes: H03F 1/0211 with control of the supply voltage or current
• CPC Class Codes: H03F 2200/541 Transformer coupled at the output of an amplifier
• CPC Class Codes: H03F 3/195 in integrated circuits
• CPC Class Codes: H03F 3/24 of transmitter output stages
• CPC Class Codes: H03F 3/68 Combinations of amplifiers, e.g. multi-channel amplifiers for stereophonics power amplifiers using a combination of several semiconductor amplifiers H03F3/211; combinations of amplifiers using coupling networks with distributed constants H03F3/602
• CPC Class Codes: H03H 7/38 Impedance-matching networks

Abstract

A circuit and method for a saturation correction of a power amplifier (PA) is provided in order to maintain a desirable switching spectrum. The circuit includes a closed loop system that is responsive to a dynamic PA control signal known as V_RAMP. The method samples a detector voltage that represents the output of the PA at the maximum voltage level of V_RAMP. The sampled detector voltage is then reduced by a predetermined amount and applied as a fixed voltage PA control signal in the place of V_RAMP. As a result, the closed loop system responds to the fixed voltage PA control signal to bring the PA out of saturation before V_RAMP can begin a voltage decrease. Once the V_RAMP voltage decreases, V_RAMP is reapplied as a dynamic PA control signal in place of the fixed voltage control signal.

Claims

1. A closed loop power amplifier (PA) control system comprising:

power amplifier circuitry adapted to amplify a radio frequency (RF) signal; and

power control circuitry adapted to provide an adjustable power control signal for controlling an output power of the power amplifier circuitry, wherein the power control circuitry is further adapted to adjust the adjustable power control signal in response to a feedback signal from the power amplifier circuitry and in response to a dynamic baseband signal having an amplitude for urging an increase in the output power of the power amplifier circuitry before the beginning of a transmission of the RF signal and for urging a decrease in the output power after the transmission of the RF signal and in response to a fixed dc signal having a voltage that urges a constant output power in place of the dynamic baseband signal during the transmission of the RF signal, wherein the fixed dc signal is derived from a sample voltage of the feedback signal by subtracting a correction offset voltage derived from the sample voltage that is taken at a predetermined time that is referenced to the dynamic baseband signal.

2. The closed loop PA control system of claim 1, wherein the power amplifier circuitry is further adapted to replace the fixed dc signal with the dynamic baseband signal in response to a decrease in the amplitude of the dynamic baseband signal.

3. The closed loop PA control system of claim 1, wherein the output power delivered by the power amplifier circuitry is decreased by a fraction of a decibel (dB) while the fixed dc signal is urging a constant output power from the power amplifier circuitry.

4. The closed loop PA control system of claim 2, wherein the sample of the feedback signal is a dc voltage and the fixed dc signal is a dc voltage signal that is slightly less than the dc voltage of the sample of the feedback signal.

5. A mobile terminal comprising:

a control system providing a dynamic baseband signal and a baseband data signal to control output power for transmitted radio frequency (RF) signals; and

communications electronics associated with the control system and comprising;

power amplifier circuitry adapted to amplify an RF signal; and

power control circuitry adapted to provide an adjustable power control signal for controlling an output power of the power amplifier circuitry, wherein the power control circuitry is further adapted to adjust the adjustable power control signal in response to a feedback signal from the power amplifier circuitry, and in response to the dynamic baseband signal having an amplitude for urging an increase in the output power of the power amplifier circuitry before the beginning of a transmission of the RF signal, and for urging a decrease in the output power after the transmission of the RF signal and in response to a fixed dc signal having a voltage that urges a constant output power in place of the dynamic baseband signal during the transmission of the RF signal, wherein the fixed dc signal is derived from a sample voltage of the feedback signal by subtracting a correction offset voltage derived from the sample voltage that is taken at a predetermined time that is referenced to the dynamic baseband signal.

6. The mobile terminal of claim 5, wherein the power amplifier circuitry is further adapted to replace the fixed dc signal with the dynamic baseband signal in response to a decrease in the amplitude of the dynamic baseband signal.

7. The mobile terminal of claim 5, wherein output power delivered by the power amplifier circuitry is decreased by a fraction of a decibel (dB) while the fixed dc signal is urging a constant output power from the power amplifier circuitry.

8. The mobile terminal of claim 6, wherein the sample of the feedback signal is a dc voltage and the fixed dc signal is a dc voltage signal that is slightly less than the dc voltage of the sample of the feedback signal.

9. A closed loop power amplifier (PA) control system comprising:

power amplifier circuitry adapted to amplify a radio frequency (RF) signal; and

power control circuitry adapted to provide an adjustable power control signal for controlling an output power of the power amplifier circuitry, wherein the power control circuitry is further adapted to adjust the adjustable power control signal in response to a feedback signal from the power amplifier circuitry, and in response to a dynamic baseband signal having an amplitude for urging an increase in the output power of the power amplifier circuitry before the beginning of a transmission of the RF signal, for urging a decrease in the output power after the transmission of the RF signal, and for urging a fixed output power during transmission of the RF signal in response to a fixed dc signal derived from a sample voltage of the feedback signal, wherein the power control circuitry is further adapted to automatically subtract a correction offset voltage from the fixed dc signal to reduce the fixed output power by a predetermined amount of offset power for power levels above a given power level during the transmission of the RF signal and for maintaining the fixed output power for power levels below the given power level during the transmission of the RF signal.

10. The closed loop PA control system of claim 9, wherein the power control circuitry is further adapted to receive a baseband data signal signifying a power level at which the power amplifier circuitry is to operate.

11. The closed loop PA control system of claim 9, wherein PA output power associated with the power levels above the given power level are calibrated to include the predetermined amount of offset power.

12. The closed loop power amplifier (PA) control system of claim 9, wherein the predetermined amount of offset power is a fraction of a decibel (dB) for the power levels above the given power level during the transmission of the RF signal.

13. A mobile terminal comprising:

a control system providing a dynamic baseband signal to control output power for transmitted radio frequency (RF) signals and providing a baseband data signal indicative of a power level at which the mobile terminal is to operate; and

communications electronics associated with the control system and comprising;

power amplifier circuitry adapted to amplify an RF signal; and

power control circuitry adapted to provide an adjustable power control signal for controlling an output power of the power amplifier circuitry, wherein the power control circuitry is further adapted to adjust the adjustable power control signal in response to a feedback signal from the power amplifier circuitry and in response to the dynamic baseband signal having an amplitude for urging an increase in the output power of the power amplifier circuitry before the beginning of a transmission of the RF signal, for urging a decrease in the output power after the transmission of the RF signal, and for urging a fixed output power during transmission of the RF signal in response to a fixed dc signal derived from a sample voltage of the feedback signal, wherein the power control circuitry is further adapted to automatically subtract a correction offset voltage from the fixed dc signal to reduce the fixed output power by a predetermined amount of offset power for power levels above a given power level during the transmission of the RF signal and for maintaining the fixed output power for power levels below the given power level during transmission of the RF signal.

14. The mobile terminal of claim 13, wherein the power control circuitry is further adapted to receive the baseband data signal indicative of a power level at which the power amplifier circuitry is to operate.

15. The mobile terminal of claim 13, wherein PA output power associated with the power levels above the given power level are calibrated to include the predetermined amount of offset power.

16. The mobile terminal of claim 13, wherein the predetermined amount of offset power is a fraction of a decibel (dB) for the power levels above the given power level during the transmission of the RF signal.

17. A method comprising:

providing a power amplifier circuitry to amplify a radio frequency (RF) signal, the power amplifier circuitry being responsive to an adjustable power control signal that dictates an amount of output power delivered by the power amplifier circuitry;

providing a power control circuitry that is responsive to a dynamic baseband signal having an amplitude for urging an increase in the amount of output power delivered by the power amplifier circuitry before the beginning of a transmission of the RF signal, for urging a decrease in the amount of output power after the transmission of the RF signal, and for urging a fixed output power during the transmission of the RF signal in response to a fixed dc signal that is derived from a sample voltage of a feedback signal, the power control circuitry being further responsive to a baseband data signal that is indicative of a power level at which the power amplifier circuitry is to operate; and

generating the adjustable power control signal in response to both the dynamic baseband signal and the baseband data signal such that the fixed output power is reduced by a predetermined amount of offset power by subtracting from the fixed dc signal a fixed correction offset voltage corresponding to the baseband data signal for power levels above a given power level during the transmission of the RF signal and for maintaining the fixed output power for power levels below the given power level during the transmission of the RF signal.

18. The method of claim 17, wherein the amount of output power delivered by the power amplifier circuitry that corresponds to the power levels above the given power level is calibrated to include the predetermined amount of offset power.

19. The method of claim 17, wherein the amount of output power delivered by the power amplifier circuitry that corresponds to the power levels above the given power level is calibrated to include the predetermined amount of offset power.

20. The method of claim 17, wherein the predetermined amount of offset power is a fraction of a decibel (dB) for power levels above the given power level during the transmission of the RF signal.