Method for controlling a linear power amplifier
View Patent ↗A linear power amplifier filters an instantaneous input signal to generate a filtered input signal, combines the instantaneous input signal and filtered input signal to generate a modified drain source voltage waveform and modulates a switched mode power supply to the linear power amplifier in accordance with the modified waveform.
1. A method of controlling a radio frequency linear power amplifier, comprising:
inputting an instantaneous input signal;
filtering the instantaneous input signal to generate a filtered input signal;
combining the instantaneous input signal and filtered input signal to generate a modified drain source voltage waveform and a modified instantaneous input signal;
modulating a switched mode power supply to the radio frequency linear power amplifier in accordance with the modified drain source voltage waveform;
driving the input of the radio frequency linear power amplifier with the modified instantaneous input signal; and
generating a clipping profile.
2. A method according to claim 1 , further comprising generating a modified output signal by multiplying the instantaneous input signal with the clipping profile.
3. A method according to claim 2 , wherein the modified drain source voltage waveform has a reduced slew rate relative to the instantaneous input signal.
4. A method according to claim 3 , wherein error vector magnitude, adjacent channel power and efficiency are adapted to optimize the modified waveform.
5. A method according to claim 4 , wherein the bandwidth of the modified drain source voltage waveform is reduced with respect to the bandwidth of the instantaneous input signal.
6. A method according to claim 5 , further comprising modifying the instantaneous input signal to keep within the modified drain source voltage waveform.
7. A linear power amplification system, comprising:
a radio frequency linear power amplifier;
a filter filtering an input waveform to produce a filtered waveform;
a combiner combining the filtered waveform with the input waveform to generate a modified drain source voltage waveform and a modified instantaneous input signal; and
a switched mode power supply powering said radio frequency linear power amplifier and modulated with the modified drain source voltage waveform, said radio frequency linear power amplifier receiving as an input the modified instantaneous input signal.
8. A system according to claim 7 , wherein said filter is a moving average filter.