Transient Band Evolution in Electromagnetic Bandgap Structures

Electromagnetic Bandgap structures (EBGs) are widely employed for microwave applications, such as filters, resonators and integrated antennas. The underlying mechanism that gives rise to these bandgaps is multiple reflections that add either destructively or constructively at the EBG pass-band and stop-band respectively. Evidently, the establishment of these multiple reflections takes a finite time interval, which has far-reaching consequences for the operational characteristics of EBGs under pulsed excitations, especially when they are integrated with RF front-ends. However, the S-parameter representation of EBGs fails to capture this effect. This paper addresses the problem of transient evolution of bands in EBGs, using the Finite Difference Time Domain (FDTD) technique, in conjunction with Time-Frequency Analysis. Wave propagation within the stop-band during the transient period of the band evolution is demonstrated. Thus, this work presents a tool that can provide critical insights for the relation between the shaping of pulses exciting an EBG-based device and its performance.