Synthesis of Energy Efficiency-Enhanced Directional Modulation Transmitters

In this article, we present new approaches to synthesize physical-layer secured directional modulation (DM) transmitters that can improve the overall energy efficiency of the system. This is achieved by creating orthogonal artificial noise (AN) that on one hand preserves signal waveforms only along desired spatial directions, and on the other hand reduces the peak to average power ratio (PAPR) of the transmitted signals. The PAPR-reduced signals become friendly to more efficient power amplifier (PA) modes (of operation), thus improving the energy consumption compared with conventional DM counterparts. In the proposed approach, reduced PAPR is achieved by applying power weighted orthogonal AN on transmitted symbols, so that the average power of signals in the RF chains is elevated, resulting in reduced PAPR. The enhancement of the total power efficiency of the transmitter, and the enhanced secrecy performance evaluated through bit error rate (BER) spatial distributions, are demonstrated through system level numerical simulation studies.