"Optimal-right" and "optimal-left" adaptive modes: keys to improving feedforward amplifier power efficiency

Two present realities in cellular base stations are communication signals of high peak-to-average ratio and the use of class AB main amplifiers in feedforward systems. The conjunction of these two factors brings out the advantages of two new modes of adaptation of the feedforward amplifier, of which optimal-right adaptation has already been reported. The superior optimal-left adaptation, here reported for the first time, decreases the drive level of the main amplifier's own intermodulation distortion increases, it is made to correlate almost perfectly with the circuit's input signal. In either case, the improved linearization performance allows a more power-efficient feedforward amplifier to be designed for a given output linearity.