Linearity improvement of microwave power amplifiers

Nonlinearity effect is the most undesirable effects in microwave power amplifier which appears in the form of harmonic distortion, gain compression, inter-modulation distortion, phase distortion, adjacent channel interference, etc. For transferring large amount of data linear power amplifiers are required which consumes less power. Modern wireless communication systems uses orthogonal frequency division multiplexing (OFDM) which has high data rate transmission capability in addition to robustness to channel impairments. One of the major disadvantages of it is having high value of peak-to-average power ratio (PAPR). High value of PAPR drives power amplifier into saturation region and causes it to operate in the nonlinear region. In this paper different power amplifier linearization and PAPR reduction techniques have been discussed. Among power amplifier linearization techniques digital pre distortion outperforms when compared with feedback and feed forward techniques. On the other hand among different PAPR reduction techniques, DFT-spread technique results in the lowest PAPR value when compared with clipping and filtering (CF), selective mapping method (SLM) and partial transmit sequence (PTS).