Envelope Factorization with Partial Elimination and Recombination, EF-PER, a New Linear RF Architecture

In this paper, a new architecture for efficient linear radio frequency transmitters is proposed; it includes envelope-tracking (ET) and envelope-elimination-and-restoration (EER) architectures as special instances. The proposed technique is referred to as Envelope Factorization with Partial Elimination and Recombination (EF-PER). It relies on a decomposition of the RF signal before power amplification as a product of two signals, one of them being the envelope signal elevated to an exponent “α”. Compared to ET or EER architectures, the parameter “α” constitutes a new degree of freedom. This allows one to realize good tradeoffs between different performance criteria such as spectrum use, power efficiency, and transmitter linearity. An intuitive aggregate cost function is introduced to capture the desired tradeoff and turns out to be maximized in α=0.5. The full relevance of EF-PER is sustained both by analytical results and realistic simulations performed for OFDM signals. The EF-PER architecture (with α=0.5) has been simulated under Agilent-ADS with a non-linear transistor model from Avago (E-PHEMT) and compared with ET and EER

The performance and efficiency of envelope elimination and restoration transmitters for future multiple-input multiple-output wireless local area networks

The inefficiency of contemporary power amplifiers ( PAs), when operating in their linear region, is a major obstacle to mobile operation of wireless local area networks ( WLANs) based on IEEE 802.11n. Therefore the use of more efficient envelope elimination and restoration ( EER) transmitter architectures is considered. In addition to high efficiency it is also necessary to satisfy the spectral mask and achieve satisfactory link- level performance. Link- level simulations of a contemporary WLAN PA show that, at the power back- offs necessary to achieve sufficient linearity, the power added efficiency ( PAE) is only similar to 1% for a system with four transmit antennas. In contrast, simulations of a phase feedback EER PA architecture show that it is possible to achieve an average PAE of 70%, while satisfying the spectral mask, with only a small degradation in link- level performance