Aperture-coupled antenna with switchable polarisation and frequency agility

The design of an aperture-coupled microstrip antenna with switchable polarisation and frequency agility is studied. Switching between two orthogonal linear polarisations (LPs) is realised by mounting two switching pin diodes on the antenna. To achieve multi-operating frequency (frequency agility) on one of the LPs, a voltage-controlled varactor diode is loaded between the top-loaded square patch and the ground plane. From the measured results, a good cross-polarisation level is observed when operated in both linear states at around 2 GHz.