Enhancing the security of communication via directly modulated antenna arrays

A new approach to enhance the security of data transmission using direction dependent antenna modulation based on an array with wide element spacing combined with directional array elements is presented. For illustrative purposes, the system investigated, and reported here, consists of an array of only two elements but the approach is general and can be extended to multi-element array systems. It is shown that by increasing the element spacing of an array the directional error rate characteristics of the system, in a given direction, can be significantly improved. Furthermore, the directly modulated system shows superior error rate performance to that of an equivalent, conventionally modulated, system in the grating lobe directions. The error rate characteristics of the proposed system are analysed for two scenarios: firstly when the angular separation between an eavesdropper and the intended recipient is small and secondly for the case when a potential eavesdropper is located much closer to the transmit antenna than the intended recipient.