Secure Antenna Polarization Modulation Line-of-Sight Analysis and Demonstration

Secure antenna polarization modulation, or SAPM, is a method for increasing security at the physical layer via spatial signal distortion. We derive its expected performance in additive white Gaussian noise (AWGN) channels with the goals of establishing theoretical limits and comparing them to other techniques in a controlled environment. The theory is verified with measurements from a proof-of-concept system, and security is evaluated using information beamwidths calculated from error probability overlook angle. Results indicate that, when compared to conventional methods and keeping the hardware consistent, SAPM has a much narrower angular range of demodulation around the intended receiver-often by over 20°, depending on the receiver's error rate threshold. Different system configurations are explored in this work, including a variety of power allocations and orders of modulation, as well as the effect of antenna design. In all cases, SAPM shows the potential to significantly improve wireless security over other techniques. These findings provide the foundation and motivation for future characterization in practical channels.