Demonstration of Directional Modulation Using a Phased Array

A four-symbol modulation is created by repeated switching of phase shifters in a phased array, in a technique known as directional modulation (DM). The phase shifts are chosen to minimize the bit error rate (BER) in a line-of-sight channel in a desired direction while maximizing the BER elsewhere. A DM transmitter is demonstrated in an anechoic chamber, and results are compared with a traditional baseband QPSK modulation using the same phased array. Experiments indicate that the DM transmitter creates a narrower region of low BERs around the desired direction than the traditional phased array while maintaining high BERs in the sidelobe regions.