Simulation Design Of Bandpass Frequency Selective Surface

Frequency selective surface (FSS) which is featured by frequency selectivity and polarization selectivity of electromagnetic waves can effectively control the transmission and reflection of electromagnetic waves.Due to the spatial filter function to the electromagnetic wave of frequency selective surface and its great theoretical significance and application value in science and engineering, it has been the subject of intensive investigation and many researchers attach more importance to this hotspot.The element type and dimension, inter-element space and the substrate parameters generally determine the frequency response, such as resonance frequency, bandwidth, and its dependence on the incidence angle and polarization. The design of FSS is a problem of optimization of multi-parameters. In order to reveal the effect of the parameters to the FSS characteristics (including resonance frequency, transmission bandwidth, transmission loss, etc.)and to provide a basis for the design of FSS,the work of this dissertation are as follows:1.Research of the size of FSS unit and the dielectric layer. Simulations have been carried out to find the relationship between the length of cross unit aperture and the resonance wavelength and effect of the unilateral and bilateral loading dielectric layer to the frequency characteristics of the FSS.When the metal screen is resonant, the dimension of the aperture is aboutλ0/2.When the thickness of the dielectric layer is comparatively small(<λ/4),two loading methods will both decrease resonant frequency when increasing the thickness of the dielectric layer. For the unilateral side loading method, when the thickness of the dielectric layer change, the resonant frequency fluctuates around f/(?) and presents periodicity with period aboutλ/2.For the bilateral side loading method, when the thickness of the dielectric layer change, the resonant frequency fluctuates around f f/(?) and presents periodicity with period also aboutλ/2.2.Design of polarization insensitive unit.The different frequency characteristics of dipole-shaped aperture unit on the TE wave and TM polarized incident wave are studied. This dissertation proposed amendment methods to the design of polarization insensitive FSS element by changing the size of aperture or dipole, and the designed FSSs show stable transmission characteristics for different polarization incident wave. For the traditional Y-shaped unit, the methods of shorten TM wave resonance pore size and extend the size of TE wave resonator are given in this paper and three pairs of polarization-insensitive Y-shaped unit are designed.Comparisons are made between the three improvements and the traditional design methods at different incident angles and simulation results show that the average of difference of TE wave and TM wave resonant frequency of the modified unit decreases by 70% compared to the traditional units.3.Design method for FSS with stable characteristics at different incident angles. Simulations have been carried out of the cross unit and a dielectric layer at different incident angles and the resonance frequency curves are given in this paper. As with the incident angle increases, the dielectric layer resonant frequency is increased. In order to design FSS with stable characteristics at different incident angles, FSS metal screen should be designed with reduced resonant frequency when the incident angle increases. Suitable shape and size meeting the above rules for the FSS unit is very important in the design process, which is very important for the design of FSS with stable characteristics at different incident angles and high performance FSS filter.4. The design of sandwich structure FSS.The sandwich structure FSS has good transmission characteristics in a large incident angle range(0°-75°)for arbitrary polarization incident wave and has a large operating bandwidth(1.4GHz). Quasi-complementary FSSs are proposed to improve the transmission anomalies of the sandwich structure FSS.5.A dual band FSS is designed using the proposed extension of TE wave resonance pore size of Y-shaped unit. For different polarization of the incident wave, the dual band FSS has the same resonant frequency and frequency band. In two working bands, dual-band FSS has a good transmission for any polarization of the incident wave in the incidence angle range 0°-60°.The main innovations of this dissertation are as follows:1.Methods to the design of polarization insensitive FSS element by changing the size of aperture or dipole are proposed.These methods can be used to the design of polarization-insensitive FSS with stable transmission characteristics for different polarization incident wave. Using the proposed method, we designed three pairs of polarization-insensitive Y-shaped unit, and the simulation results show that the average of difference of TE wave and TM wave resonant frequency of the modified unit decreases by 70% compared to the traditional units, which shows that the design methods are feasible.2.A new method using quasi-complementary unit for the design of multilayer FSS is proposed. A FSS is given designed using quasi-complementary unit which shows good transmission characteristics in the incident angle range 0°-60°for both of the TE wave and TM wave.3.A dual band FSS is designed using the proposed extension of TE wave resonance pore size of Y-shaped unit. For different polarization of the incident wave, the dual band FSS has the same resonant frequency and frequency band of 1.5GHz and 0.4GHz respectively. In two working bands, dual-band FSS has a good transmission for both of the TE and TM incident wave in the incidence angle range 0°-60°.4. On the design of the FSS with stable characteristics at different incident angles, the paper pointed out that FSS metal screen should be designed with reduced resonant frequency when the incident angle increases, which is very important for the design of FSS with stable characteristics at different incident angles.