Design Of Broadband Frequency Selective Surface And Their Application

Frequency Selective Surface(FSS)is a kind of periodic structure.Based on its own resonance characteristics,it has the function of selective reflection or transmission of electromagnetic wave energy in different frequency bands.In theory,FSS is composed of an infinite number of metal resonant elements.There are single or multiple layers in FSS structure.The resonant elements that make up the FSS are generally divided into two types: patch type and aperture type.Near the resonant frequency,the elements of the two types exhibit total reflection or total transmission properties.Therefore,using different elements can achieve different filtering effects.Militaryally,the FSS is usually applied to the radome of an aircraft,which can effectively reduce the radar cross section(RCS)of the aircraft antenna.The FSS can also be applied to a reflector antenna,which allows multiple antenna feeds to share one main reflector,which greatly improves the utilization of the parabolic antenna.The FSS also has a wide range of uses in other areas,ranging from many aspects of the electromagnetic field,such as planar high-gain antennas,electromagnetic shielding materials,electromagnetically absorbers,polarization converters,and the like.This shows that both in military technology and civil technology,FSS has a wide range of application value.This thesis studies the design principle of FSS,mainly analyzes and discusses broadband FSS and its applications,angular-stable FSS and miniaturized FSS.The author's main work is as follows:First,the analysis methods and design principles of FSS are introduced.Through the simulation of some simple FSS units,the affects of the main parameters on the frequency response is analyzed,and the main performance of some basic FSS units is briefly summarized.Secondly,a dual-layer cascading method is used to design a broadband band-stop FSS with a bandwidth of 5.5 GHz.The out-of-band transmission performance is good.It replaces the metal reflector of the bow-tie antenna and is used to reduce out-of-band RCS.Simulation results show that the radiation performance of the antenna is not affected,and out-of-band RCS is effectively reduced.Again,by combining two FSS units,a single-layer angular stable FSS unit is proposed.The simulation results show that the FSS unit can maintain the resonant frequency at the incident wave angles of 0-85°,and its equivalent circuit is used to analyze the FSS.A set of formulas for calculating its equivalent circuit parameters is given.After the FSS is processed,the transmission coefficient of the FSS is measured in the anechoic chamber.The measured results show that the FSS has good angle stability.Finally,according to a simple bandpass resonant circuit,a design method of miniaturized bandpass FSS is proposed,which corresponds the structure in the FSS unit with the capacitance and inductance in the circuit.This method can simplify the design of the bandpass FSS.The HFSS simulation results are in good agreement with the circuit simulation results.However,the angle stability of the simple FSS unit is not good.Based on the design method,two FSS units with improved angle stability are proposed and the equivalent circuit is used to analyze its resonant principle.A 2.5-D miniaturized FSS was designed by means of meander line technology and metallized vias.The design principle was analyzed and the effects of the main parameters on its miniaturization was studied.The HFSS simulation results show that the miniaturization of the FSS is can up to 0.035?.