Grating lobe suppression in focussed energy delivery for precision electronic warfare

Focussed energy delivery (FED), which transmits energy to a specific area by ultrasparse arrays, is the core technique of precision electronic warfare (PREW). However, array sparsity results in severe grating lobes in practice, which greatly increase the risks of an interference system being attacked and unexpected jamming occurring in other devices. Here, two methods are presented which are aimed at suppressing grating lobes when implementing FED in the application of PREW to avoid the problems mentioned. Regarding the first method, a new metric based on the l ∞ -norm is proposed to measure the maximum grating lobe and introduce the metric to the standard FED model. A multiobjective optimisation problem (MOP) is established and solved by the alternating direction penalty method (ADPM) framework. In the second method, the degrees of freedom of the transmitted signals are extended by equipping each platform with a group of linear uniform antennas. The corresponding MOP is established and block coordinate descent is employed to simplify the problem into two subproblems concerning the amplitude and phase components of the transmitted signals. Then, these two subproblems are solved using Taylor expansion and the ADPM framework. Simulation results are provided to demonstrate the advantages of the proposed methods over the state-of-the-art methods.