Null Forming in Distributed Transmit Array Patterns

Collaborative transmit beamforming using coherent distributed arrays is a method by which multiple wireless nodes synchronize their transmissions in order to synthesize a virtual antenna array. This technique gives directional transmit ability to disadvantaged nodes in a wireless network that have size, weight, and power (SWaP) constraints, which in turn would allow the network to communicate over longer ranges and with greater efficiency. The distributed array gain in arbitrary directions outside of the main beam is aperiodic and unpredictable for an aperiodic sparse array, which represents the configuration of a typical wireless sensor network (WSN) or mobile ad hoc network (MANET). In this paper, we examine a null forming approach for planar distributed arrays that uses global heuristic optimization to adjust the positions of nodes to minimize radiation in a specified direction while maintaining the main beam. Simulations are used to track null depth and width over several scenario iterations. We also examine how node localization uncertainty affects manufactured nulls.