Susceptibility of an Electromagnetic BandGap Filter

In a compact dual-planar electromagnetic (EM) bandgap (EBG) microstrip structure, patches are etched periodically in the ground plane to prohibit the propagation of EM waves in certain frequency bands so as to provide filtering functionality. However, the existence of the etched patches in the ground plane becomes a concern in terms of EM compatibility (EMC) and EM susceptibility (EMS). These structures might be prone to EM interference from nearby circuit components as compared to a microstrip filter with a perfect ground plane. In this paper, we study the EMS of a dual-planar EBG filter structure to a microstrip line in close proximity. This study examines the coupling effects of a nearby microstrip line on the performance of the EBG structure when the microstrip line is transmitting a signal and when it is not transmitting a signal. When the microstrip line is transmitting a signal, the effects of the working frequency and the direction of the signal on the coupling to the EBG structure are studied. Experimental and numerical work are presented, analyzed, and verified. The results obtained are useful for the applications and integrations of EBG microstrip structures to microwave circuits. They are useful for EMC and EMS studies of other patterned ground structures/defected ground structures.