Design of a simple circularly polarised dual-frequency reconfigurable microstrip patch antenna array for millimetre-wave applications

Reconfigurable antenna array has received a lot of attention in present-day wireless communication systems. In this study, a simple design of a four-element circularly polarised dual-frequency reconfigurable microstrip patch antenna array for millimetre-wave applications is proposed. The sequentially rotated series-parallel stub approach is employed in the feeding network design to provide symmetrical array elements positioning, and bringing about a good axial ratio of polarisation. Additionally, a matching branch per element is employed to generate spatial flexibility for element positioning and good impedance matching. Furthermore, due to high-cost constraints of Ka-band RF switches (such as PE42524 SPDT), switches are considered as transmission lines, and are placed within the fractal slots of each elements to reconfigure the frequency. The proposed array operates in two switching states: ON and OFF. Hence, it allows dual-frequency reconfigurability of 27 and 35 GHz for the ON and OFF states, respectively. A full array prototype was then fabricated on a Rogers R5880 substrate and tested in an anechoic chamber. Simulation and measurement results corroborate quite well in general. Patch antenna array gives much better result characterised by reconfigurable behaviour with associated return loss, radiation pattern characteristics, and < 3 dB axial ratio polarisation bandwidth than the single element. The proposed antenna array finds good applications in radar systems, satellite communications, and aerospace.