Linear Power Amplifier Uses Mirror Predistortion

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  • Author: K. Fayed, A. Ezzeddine, H. Huang, A. Zaghloul
Current wireless communication standards have been established to carry voice, data and video with high data rates. These high data rates require efficient modulation techniques such as OFDM 64 QAM, to allow transmission in a given finite bandwidth. With these types of modulation, there are probabilities that at certain times, the voltages of the multiple carriers are in phase and their amplitudes add up to create a very high peak to average ratio (PAR) that may reach 15 dB. This high PAR will drive a conventional PA into saturation; causing signal distortion and generating out-band interference. One way to solve this problem is to use a high power PA in Class A mode, with average power set at a back off (BO) of 10-12 dB. Unfortunately, this technique results in a very inefficient PA.