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

摘要

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 VRAMP. The method samples a detector voltage that represents the output of the PA at the maximum voltage level of VRAMP. The sampled detector voltage is then reduced by a predetermined amount and applied as a fixed voltage PA control signal in the place of VRAMP. As a result, the closed loop system responds to the fixed voltage PA control signal to bring the PA out of saturation before VRAMP can begin a voltage decrease. Once the VRAMP voltage decreases, VRAMP is reapplied as a dynamic PA control signal in place of the fixed voltage control signal.

主权项

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.