Filters based on spoof surface plasmon polaritons composed of planar Mach-Zehnder interferometer

Filter characteristics of a planar Mach-Zehnder interferometer (MZI) structure composed of periodically thin corrugated metal films were studied here. From theoretical simulation, spoof surface plasmon polaritons can propagate along the periodically thin corrugated metal films in microwave frequency, which can be excited by a coplanar waveguide. When the two arms of the MZI have the same length with the angle between them being 60 degrees, the MZI structure has a very wide bandwidth with 8.6 GHz. By changing the length of one of the interference arms, a novel low-pass filter based on the planar MZI structure with two notched frequencies was proposed. The proposed planar structure can find potential applications in developing surface wave devices in integrated microwave circuits and systems.