A linearizing predistorter with fast adaptation

An adaptive predistorter particularly suited to baseband implementation with digital signal-processing hardware is presented and analyzed. It is applicable to any modulation format and any AM/FM and FM/PM characteristic. With a table of well under 100 complex words, it reduces intermodulation products in a typical Class AB amplifier to levels suitable for the mobile environment. It adapts to a new amplifier in a few milliseconds, and its reconvergence time following a channel switch is virtually zero. Since it allows linearization of the power amplifier over 95% to 98% of the saturated output power, it provides power efficiency as well. In comparison with the most powerful predistorter previously reported, it requires four orders of magnitude less memory, reduces convergence time by over three orders of magnitude, eliminates reconvergence time following a channel switch, and eliminates the need for a phase shifter in the feedback path