Secure physical-layer communication based on directly modulated antenna arrays

An antenna system configured to provide direction dependent modulation is shown to increase the security of data transmission. The antenna is based on an array with wide element spacing combined with directional array elements. The array system investigated here consists of only two elements but the approach is general and can be extended to multi-element array systems. The directional error rate characteristics of the directly modulated array system, in a given direction, can be significantly improved by increasing the element spacing. The error rate performance of the directly modulated array system is compared to that of an equivalent array configured for conventional baseband modulation.