A novel 2nd-order bandpass MFSS filter with miniaturized structure

In order to effectively obtain a miniaturized structure and good filtering properties, we propose a novel 2nd-order bandpass metamaterial frequency selective surface (MFSS) filter which contains two capacitive layers and one inductive layer, where there are multi-loop metallic patches as shunt capacitor C and planar wire grids as series inductor L respectively. Unlike the traditional operation way—the tuned elements used in resonant surface approximately equal to one wavelength in circumference and the structure thickness with a spacing of a quarter wavelength apart, by changing the value of L and C and matching multilayer dielectric to adjust the LC coupling resonance and the resonance impedance respectively, the proposed MFSS filter can achieves a miniatured structure with ideal bandpass properties. Measurement results of the fabricated prototype of the bandpass filter (BPF) indicate that the dimension of the tuned element on resonant surface is approximately 0.025 wavelength, i.e., 0.025λ. At the same time, the filter has the stable center frequency of f0 = 1.53GHz and the transmittance of T ⩾ 96.3% and high Q-value for the TE/TM wave polarization at various incidence angles. The novel 2nd-order bandpass MFSS filter with miniaturized structure not only can decrease structure dimension, but also has a wide range of applications to microwave and infrared band.