Simple predistortion system for compensation of temperature dependent nonlinearity of power amplifiers

A change of ambient temperature is a crucial disturbing factor in predistortion systems. This paper presents a simple way to linearize a power amplifier with only one characteristic (AM-AM and AM-PM curve) over the entire temperature range. All characteristic curves measured at different temperatures can be mapped by means of scaling factors to only one resultant curve. The predistortion can be done with the inverse of that resultant curve and the determined scaling factors. The specifications of EDGE standard were chosen to prove the performance of the proposed system. The improvement in linear output power (concerning spec. limit of EVMrms: 8.3 dB and spectral regrowth @400 kHz offset: 3.7dB) is shown to be constant over the entire temperature range from -30°C to 90°C. These are the maximum reachable improvements which confirm the precise operation. This predistortion approach is also valid for volterra series models and their derivative models.