An iterative pattern synthesis approach for directional modulation (DM) transmitters is presented in this study. Unlike all previous work, this study offers the first discussion on constraining DM transmitter far-field radiation patterns so that energy is primarily concentrated in the spatial direction where low bit error rate is to be achieved, while interference projected along other directions is reduced.
Ding, Y., & Fusco, V. F. (2014). Constraining directional modulation transmitter radiation patterns. IET Microwaves, Antennas and Propagation, 8(15), 1408-1415. https://doi.org/10.1049/iet-map.2014.0042