This document provides guidelines for designing a power amplifier to achieve optimum performance with Maxim's radio frequency (RF) power amplifier (PA) linearizer (RFPAL) or other types of predistortion. Using RFPAL products (SC1894 and SC2200), an optimally-tuned PA can achieve up to 28dB of correction; thereby, allowing the amplifier to operate at the highest possible efficiency. Conversely, a PA which has not been optimized for operation with a linearizer could achieve little-to-no improvement in linearity and it could fail to meet the spectral requirements.
The majority of RF PAs deployed in wireless infrastructure applications use either a Class AB or Doherty architecture. Class AB PAs are commonly used in microwave backhaul applications or in very low antenna-output power applications and are dynamically biased between Class A and Class B. They are a compromise between linearity, output power, efficiency and cost. On the other hand, Doherty PAs are used to deliver high power at high efficiency using high-PAR signals, but they require the use of linearization technology to meet the spectral emissions mask requirements. RFPAL can be applied to both types of amplifiers to achieve better efficiency and linearity results.