Optimization for error-canceling loop of the feedforward amplifier using a new system-level mathematical model

We present a system-level mathematical model to simulate the linearity of the feedforward amplifier. The model has fundamental and distortion signal sub-paths constructed from the data extracted by baseband system simulation. The calculated linearization performances using the model have been validated by comparison with the baseband system simulation results. From the calculated results, the optimum design of the error amplifier size and coupling factor of the output coupler for a down-link WCDMA signal with 16 data channels are provided to maximally achieve output linearity with a fixed power capacity of the amplifiers. Our data shows that the optimum size of the error amplifier is 0.45 times that of the main amplifier with the coupling factor of 5.5 dB.