Linearity Improvement Techniques for Wireless Transmitters: Part 2

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  • Author: Andrei Grebennikov
The reflect forward adaptive linearizer (RFAL) technique uses the input reflected signal from one power amplifier to develop an intermodulation-correcting signal forwarded to the input of the other power amplifier which are connected in parallel or balanced configuration.the RFAL amplifier which includes the two identical power amplifiers, a low-distortion booster amplifier, forward and reflected paths with two directional couplers at the input, and delay line and inphase combiner at the output. With the RFAL technique, the power combining efficiency of the two power amplifiers approaches that of the conventional parallel power amplifier configuration, while the intermodulation products can be improved from 20 to 30 dBc at the center bandwidth frequency.