A Dynamic Phased Array for Steerable Secure V2X Wireless Communications

In this letter, we present a compact and efficient dynamic antenna array system for vehicle-to-everything (V2X) communications applications that is capable of steering a spatially narrow information beam to provide increased wireless security at the physical layer. The technique is demonstrated in both indoor and outdoor environments with a 2.5 GHz $1\times2$ patch antenna array with $0.5\lambda$ spacing with an amplitude imbalanced feed using a Wilkinson divider and an in-series double-pole-double-throw (DPDT) RF switch. Switching the outputs of the divider rapidly between the two antenna inputs induces an electrical motion of the phase center along the axis of the array, creating directional modulation that increases the bit error ratio (BER) towards undesired directions, but maintains zero BER at the desired direction. Traditional phase weighting can be used to steer the uncorrupted information to an arbitrary direction. Wireless communication security is demonstrated using 16-QAM modulation transmitted in 48-kbit bursts. The data stream is a pseudo-random bit sequence (PRBS) transmitted at a rate of 4 Mb/s. The DPDT RF switch was driven three orders of magnitude slower at a rate of 1 kHz. The communication system operated at a minimum SNR of 25 dB so that any bit errors were due to the phase and amplitude dynamics, and not due to low SNR. The dynamic array obtained a low BER of $10^{-3}$ within an information beam of $25^\circ$ at broadside, and $\sim45^\circ$ when the array is steered to $\pm 30^\circ$, while a traditional static array yielded low BER at all angles (no wireless security.