A programmable analog polynomial predistortion circuit for linearising radio transmitters

An analog 5th order polynomial predistortion circuit with programmable coefficients has been integrated in a 0.8 µm BiCMOS process. The distorter circuit consists of nine bipolar Gilbert cell mixers, and it is capable for linearising power amplifier at baseband or IF. A test setup consisting of two distorter ICs, digital programming interface and summing amplifiers has been built and tested at an IF frequency of 20.4 MHz, and 20..25 dB reduction in third order intermodulation results is achieved.