Dual-band Frequency Selective Surface

The design of multiband frequency selective surfaces (FSS)has attracted much attention because of the increasing demands on multifunctionality for communications and detections. This dissertation focuses on dual-band FSS such as FSS loading with lumped capacitors, Y-loop dual-band FSS and MMW/IR dual-band FSS.The numerical simulation, establishing of the equivalent circuit model and the design and fabrication of FSS have been carried out.The main contributions of this dissertation are listed as following:1.The performance of ring-loop-slot FSS loading with lumped capacitors has been analyzed and empirical formulas for calculating resonance frequency in the range of 1-4GHz is presented, which provides an effective solution for quick design of the FSS.2.A novel equivalent circuit model of the ring-loop-slot FSS loading with lumped capacitors is proposed and the analytic calculation formulations describing the relationship between the physical parameters and the equivalent L, C elements are given, which makes the design of FSS convenient and effective.Furthermore, the frequency behavior of the loaded FSS has been illustrated in the model which provided theoretical principle for the study of the loaded FSS.3. Based on the theoretical research, a ring-loop-slot FSS loading with lumped capacitor has been designed with the resonance frequency of 2.45GHz. Simulation and experimental results indicate that the dimension of the loaded FSS can be miniaturized to 34 percent in comparison with the traditional FSS.As the angle of incidence increases from 0°to 60°the shift of resonance frequency is less than 0.5%.4.For Y-loop fractal FSS element, it is difficult to get perfect frequency responses in a wide band for the onset of the grating lobe.To solve this problem, a novel dual-band FSS based on Y-loop is proposed. Simulation and experimental results show that there is no other resonance frequency from 1OGHz to 40GHz expect the desired frequency(12.5GHz and 35GHz) which indicates that the novel multiband FSS has eliminated the parasitic resonance compared with the Y-loop fractal element.5.In MMW/IR dual-mode seeker, the dome must pass both infrared radiation and millimeter wave so that a novel frequency selective surface with dual passband for MMW/IR application is investigated. In order to transmit IR wave,the metal film of traditional FSS is replaced by a semiconductor film which is transparent for IR, and the optimization of the structure is studied.Numerical results show that the transmission of designed FSS at 8mm band reaches 90%.Furthermore, the high transmission of IR is ensured because the surface coverage of metal is less than 9%.