PSLL and HPBW Minimisation in Time‐Variant FDA Using Sum‐of‐Sinc‐Functions‐Based Frequency Offsets

Beampattern of a frequency diverse array (FDA) is a function of time, range and angle. The shape of this beampattern is dependent on the frequency offsets (FO) that are applied to each element. These FO are sampled from a window function whose parameters are optimised to yield minimum peak side lobe level (PSLL) and half‐power beamwidth (HPBW). Time‐variance is usually ignored because it can be removed by signal processing at the receiver. However, the travelling beam is still time‐variant. This work shows that, in a time‐variant beampattern, the optimum PSLL of these window functions degrade while HPBW is unaffected. A window function that is based on a sum of three Sinc functions (s‐Sinc) is proposed for FO optimisation. The superiority of this window is established by comparing the optimum PSLL and HPBW in a time‐invariant scenario. Later, time‐variance is introduced, and s‐Sinc function is used to minimise time‐variant PSLL and HPBW. Results show that a beampattern with low time‐variant PSLL and HPBW can be synthesised compared to their time‐invariant counterparts.