An Adaptive Feedforward Amplifier Under “Maximum Output” Control Method for UMTS Downlink Transmitters

An adaptive feedforward amplifier is implemented for a Universal Mobile Telecommunication System (UMTS) downlink channel (2110–2170 MHz). An exhaustive characterization of the space of solution has corroborated the feedforward theoretical behavior. As a result, an alternative adjustment method is proposed, called “maximum output,” which entails maximizing a specific designed objective function. Besides this, an adaptive control system, based on distortion signal minimization architecture, has been fabricated in order to apply the designed method. The overall system performance achieves significant improvements such as 16.7 dB on the third-order intermodulation product, measured with a 5-MHz separated two-tone signal, 15 dB on the adjacent channel leakage ratio level and 2.7 dB on the output power level, both of them obtained with UMTS test model 1 (64 channels). The maximum output control method allows fulfilling any standard linearity specification while power efficiency is maximized so the desired tradeoff between linearity and efficiency is achieved.