Patent ID: 8718580

Claim:
A system for providing an amplified radio frequency (RF) signal representing a baseband input signal, the system comprising: a first amplifier, on a first signal path, configured to amplify a first intermediate signal to provide a first amplified signal; a second amplifier, on a second signal path, configured to amplify a second intermediate signal to provide a second amplified signal; a third amplifier, on the second signal path, configured to amplify the second intermediate signal to provide a third amplified signal; a signal combiner configured to combine the first amplified signal, the second amplified signal, and the third amplified signal to produce the amplified RF signal; and an RF modulator configured to modulate an RF carrier signal with a baseband input signal to provide the first intermediate signal on a first signal path and the second intermediate signal on the second signal path, the RF modulator providing the first and second intermediate signals such that the first amplified signal is out-of-phase with each of the second and third amplified signals at an output of an active device within the second amplifier when the amplitude of the baseband input signal exceeds a first threshold voltage and the first amplified signal is in phase with each of the second and third amplified signals at the output of the active device within the second amplifier when the baseband input signal is below the first threshold voltage; wherein the RF modulator is further configured to provide the second intermediate signal only when the baseband input signal amplitude is above a second threshold voltage, higher than the first threshold voltage, such that the first amplifier is active and the second and third amplifiers are not active, and to provide the first intermediate signal to the first amplifier such that the amplitude of the first amplified signal increases substantially linearly with the amplitude of the baseband input signal when the amplitude of the baseband input signal is below the first threshold voltage, decreases as the amplitude of the baseband input signal increases when the amplitude of the baseband input signal is between the first threshold voltage and the second threshold voltage, and increases, but is out-of-phase with each of the second and third amplified signals, when the amplitude of the baseband input signal exceeds the second threshold voltage.