Guided-wave characteristics of waveguide based periodic structures loaded with various FSS strip layers

In this paper, frequency-dependent guided-wave characteristics of waveguide based periodic structures loaded with transversal strip layers of frequency selective surfaces (FSS) are extensively studied in terms of per-unit-length transmission parameters, i.e., complex propagation constant and complex wave impedance. Such a periodic structure with various FSS strip layers are in theory characterized using the hybrid method of moments (MoM)-immittance approach so as to derive these two per-unit-length parameters over a wide frequency range. At first, the extracted phase constant of a simple periodic waveguide, loaded with rectangular patch layer, is compared with the available analytical results, thus validating the approach utilized here. Next, the three novel periodic waveguides, loaded with plus, square loop and Jerusalem cross FSS strip layers, are investigated. It is observed that there is slow-wave behavior in the lower passband for the first two whereas the third one exhibits both fast-wave and slow-wave propagation behaviors in the lower passband. Besides, the third one shows the attractive backward wave propagation within the partial passband, thus introducing a novel waveguide-based artificial negative refractive index metamaterial (NRIM).