Optimising the performance of an optically controlled microwave switch

Optical control of microwave switches is an appealing concept for use in reconfigurable antennas as it eliminates the need for metallic biasing lines which may affect the performance of the wireless system. The ultimate goal of this study is to minimise insertion loss of a photoconductive microwave switch in the ON state whilst maintaining high isolation in the OFF state. Firstly, a parameter simulation study using different substrate materials, thicknesses and gap widths is presented to obtain optimised S21 results. The best performance is from a 1.2mm line using a 0.3mm gap. Secondly, the effect of passivation and texturisation on the photoconductivity and microwave performance of the silicon die is investigated. Passivation of the sample decreases insertion loss, however texturing the surface increases loss.