An adaptive feedforward power amplifier for UMTS transmitters

The new communication standards like UMTS increase the spectral efficiency but a high linearity is required. RF power amplifiers are basic components of all wireless transceivers used in the communication systems, and their efficiency directly influences on the complete communication system efficiency. It is proposed the implementation of a linearization technique like feedforward to achieve lower cost and higher efficiency amplifiers with the same linearity. First, it is shown an adjusting method for balancing the amplitude, phase and delay elements in both loops of the feedforward architecture during the prototyping. Secondly, a prototype for UMTS downlink has been developed. This implementation demonstrates that with dynamic adjustment architecture and the proposed method, the linearity level is increased outstandingly in the range of -20 to 70 °C. For a two tone signal separated 5 MHz the IMD3 raise is 37.5 dB and for a UMTS signal (test 1-64 channels) the ACPR increase is 15 dB.