Signal processing techniques for 3G wireless power amplifier

Summary form only given. Today´s 3G wireless systems require both higher linearity and high power amplifier efficiency. The high peak-to-average ratios (PARs) of the digital modulation schemes used in 3G wireless systems require that the RF power amplifier (PA) maintain high linearity over a large range while maintaining this high efficiency, these two requirements are often at odds with each other with many of the traditional amplifier architectures. Linearity is achieved often by either reducing efficiency or by using linearization architectures such as feedforward or outphasing techniques. For class A or class AB power amplifiers, ´backing off´ the input can improve linearity, but this reduces power efficiency and increases heat dissipation. This improvement in linearity results in an increase in power consumption, thus it is not a viable tradeoff. The discussion today focuses on baseband signal processing approaches which are being used to reduce the high PARs, increase PA linearity, while also mitigating impairments in high powered PAs, thus allowing for higher efficiencies while maintaining linearity requirements. This talk discusses PA impairments, introduces crest factor reduction (CFR) and digital predistortion (DPD) both of which are used to increase PA module efficiencies. CFR and DPD uses digital signal processing (DSP) techniques to predistort a baseband signal before modulation, up-conversion, and amplification by the PA.