Reconfigurable electromagnetic band gap based structures with defects for MM wave and antenna applications

There has been increasing interest in the field of electromagnetic band gap (EBG) materials . This is due to the fact that EBG structures have unique frequency selective properties and vast number of applications in microwave, millimeter wave and optical devices. This paper presents a study of a tunable planar EBG based structure with defects introduced in specific areas. The defects considered are in form of element discontinuities and varying element dimensions. The circuit has been realised by placing a transmission line across a periodic array of dipoles on grounded dielectric substrate. The photoconductive properties of silicon are utilised to alter the dimensions of the elements resulting in the reconfigurable stopband. The ability to adaptively control the circuit by switching on and off the element defects using optical illumination has been the predominant factor influencing the choice of the design. We have obtained both predicted and measured results up to 20 GHz for the performance and behaviour of the EBG structures. Overall, the agreement between the measured and the predicted results have been good.