Sub-millimeter Wave Frequency Selective Surface Filter

Frequency selective surfaces(FSSs)as filters have more advantages than conventional filters in millimeter wave and Sub- millimeter wave band, so frequency selective surface filters are applied widely in military and civilian area. Two type structures of frequency selective surfaces are designed and studied in this paper.First, the theoretical analysis and designed method of frequency selective surfaces are summarized and a novel frequency selective surface in 3 millimeter wave band is presented in this paper. The influences of arm length, arm width, dielectric constant, incidence angle, incidence wave polarization of the frequency selective surface on frequency response characteristic are simulated by HFSS. The results show that the frequency selective surfaces have very good angle and polarization stability within the±25o range, so the frequency selective surface has very good filtering characteristics. According to the simulation results, two single layer substrate frequency selective surfaces with arm length 3.1mm and 3.3mm are fabricated and tested. The center resonant frequencies of FSS with arm length 3.1mm and 3.3mm obtained in experiment are 96.2GHz and 96.05GHzs, respectively. The experimental result has a little deviation comparing to stimulation because of the fabrication precision of the arm length. Good angle and polarization stability of the FSSs in experiment are in agreements with stimulation result.Because of traditional frequency selective surfaces only with one fixed resonant frequency point, a reconfigurable frequency selective surfaces filter with MEMS switch on each arm is designed. The influence of these switches sates on frequency response characteristic is simulation by HFSS. The resonant center frequency of the reconfigurable frequency selective surface is 220GHz and can be changed by controlling each switch sate on the arm. The results of simulation show that the resonant frequency can be changed with the variation of arm length and increased bandwidth in 220GHz-230GHz. Finally, the influence of incidence angle and incidence wave polarization pattern on frequency response characteristic is studied and it is found that the frequency selective surface has very good angle and polarization stability within the 45o range.