Ultra-wideband harmonic-suppressed bandpass/stop frequency-selective surface based on L-C lumped elements

Ultra-wideband harmonic rejection bandpass and bandstop frequency-selective surfaces (FSS) based on LC lumped elements are proposed. The bandpass response is achieved by parallel combination of LC resonant circuit. While the bandstop one is accomplished by series combination. Detailed analysis with the aid of an equivalent circuit models is provided to explain the operating principles and parasitic effects for both FSSs. Bandwidths of 19:1 and 24.5:1 harmonic rejection are achieved between the fundamental frequency and the first harmonic for bandpass and bandstop FSSs, respectively. Controllable resonant frequency and bandwidth are possible by controlling the lumped element's value. To validate the simulated results, a bandpass FSS prototype is fabricated and measured. It is shown that this methodology is suitable for low frequencies due to the parasitic capacitor associated with the lumped inductor at high frequencies and the change of the component's value with frequency.