Directional modulation for QAM signals with PAPR reduction

Directional modulation (DM) is a promising technology for physical layer security. Traditional DM methods ignored the issue of the decomposed signals' peak-to-average power ratios (PAPRs), which may lead to poor amplifier efficiency since high back-off power is required. To improve amplifier efficiency, a PAPR reduction concept is proposed for DM of QAM signals in this paper. An iterative projection method is implemented to guarantee secrecy performance and low PAPRs simultaneously. Simulation and experimental results show that, comparing with traditional DM method, the proposed approach has almost the same secrecy performance but reduces the PAPR of transmitted signal for each antenna element by about 5.6dB to 7.9dB.