Development and design of multi-band bandpass filter based on the concept of spoof surface plasmon polaritons

In this paper, we report a multi-band bandpass filter based on the concept of spoof or designer surface plasmon polaritons (SSPP's). When metal surface is corrugated with periodical grooves, it support surface plasmon polaritons mode at microwave frequency which is known as designer or spoof SPP's. An efficient conversion is required from QTEM mode of microstrip to SSPP mode, to feed energy into and extraction of signal from plasmonic structure. In this work first a transition device is implemented using the gradient corrugated strip, in which SSPP wave is highly confined at the teeth part of the corrugated surface. After then, its response is recorded by inserting a complementary split ring resonator (CSRR) in ground plane. With these CSRR rings, the device shows excellent bandpass filtering characteristics. The proposed devices are designed and fabricated. Simulation and measurement results of reflection and transmission coefficient are in good agreement at microwave frequency.