A Phase‐Only Hybrid Optimisation Method for Sparse Circularly Polarised Arrays

A multiobjective phase‐only design method, COMO‐PHO (coevolutionary multiobjective with phase‐only hybrid optimisation), is proposed for synthesising sparse circularly polarised phased arrays. The method introduces element rotation to improve circular polarisation and adopts a dual‐population coevolutionary framework. This framework decomposes the high‐dimensional optimisation—covering element selection, excitation phase and rotation angle—into coordinated placement and rotation optimisation, whilst jointly minimising sidelobe levels and axial ratio. A fast phase‐only solver embedded in the evolutionary process quickly evaluates candidate layouts. Once the placement is fixed, a phase‐only convex optimisation algorithm refines the phase distribution using the solver output as the initial solution, achieving precise beam steering and low sidelobes through controlled phase perturbation and linearised constraints. Simulations confirm that COMO‐PHO balances multiple performance metrics for wide‐angle scanning, offering a cost‐effective solution for sparse circularly polarised phased array design. Furthermore, its effectiveness has been validated using measurements from an circularly polarised phased‐array prototype, demonstrating the method's practical feasibility under real hardware conditions.