Research On Miniaturized Reconfigurable Frequency Selective Surface

The frequency selective surface can selectively reflect and transmit electromagnetic waves,playing an important role in stealth design,solving electromagnetic interference,and improving antenna performance.In order to improve the stealth capability of the device,a radome made with a frequency selective surface can effectively reduce the radar cross section(RCS)of the antenna,and is widely used.With the development of science and technology,radar detection technology is becoming more and more advanced,and the difficulty of stealth design is getting higher and higher.The traditional frequency selective surface can no longer meet the needs of current stealth technology.The reconfigurable frequency selective surface realizes the change of transmission characteristics through the control of active devices,which can meet more complex application environments.In this thesis,the design method of reconfigurable frequency selective surface is studied,and the miniaturized design of reconfigurable frequency selective surface is carried out.In addition,the application of the reconfigurable frequency selective surface is studied and combined with the antenna design,the function of the antenna is enriched.1.In order to expand the bandwidth of the frequency selective surface,a low-profile broadband frequency selective surface is designed based on the non-resonant structure.The designed frequency selective surface adopts the design idea of a second-order filter.The second-order filter is formed by cascading the non-resonant structure.It has two resonance points and has a wide working bandwidth.While increasing the bandwidth of the frequency selective surface,solving The problem of too high profile caused by cascade is solved.In the design,the miniaturization of the unit is increased through the interdigital technology,and the performance of the frequency selective surface is improved.The frequency selective surface has the characteristics of broadband,low profile,and high degree of miniaturization.2.The use of cascade technology can increase the bandwidth of the frequency selective surface,and the switch-type reconfigurable frequency selective surface must take into account two working states when increasing the bandwidth through the cascade technology,which increases the complexity of the design.This thesis selects the same unit cascade,uses the increased equivalent capacitance value of the diode off state to increase the resonant frequency and introduces high-frequency resonance,which increases the stopband bandwidth without destroying the passband performance,and solves the problem that it is difficult to coordinate and unify the pass stopband in the process of reconfigurable frequency selective surface expansion bandwidth.In this thesis,a double-layer reconfigurable frequency selective surface is designed.The working frequency band basically completely covers the X-band.The transmission state is controlled by controlling the on-off of the diode,and the bending structure is used for miniaturization.Finally,an improved reconfigurable frequency selective surface is designed.Compared with the previous broadband reconfigurable frequency selective surface,the bandwidth has been significantly improved,and the angle stability is more excellent.3.Aiming at the problem that the reconfigurable frequency selective surface is difficult to miniaturize,this paper designs a multifunctional miniaturized low-profile reconfigurable frequency selective surface.The designed reconfigurable frequency selective surface uses a self-complementary structure to achieve pass-stop band conversion,and has the characteristic of consistent pass-band and stop-band resonance frequencies.The use of interdigital technology effectively increases the miniaturization of the unit.Since the unit uses two layers to control the two polarization directions separately,the polarization selective function is added to the reconfigurable frequency selective surface,and it has a total of four working states.The designed reconfigurable frequency selective surface has high miniaturization,low profile and good angular stability.In order to simplify the bias network,the unit itself is used as a bias line to reduce the influence of the bias network on the performance of the frequency selective surface.4.Combining the reconfigurable frequency selective surface with the antenna can improve the performance of the antenna.In this thesis,the reconfigurable frequency selective surface is combined with the transmission array and the reflection array antenna to design a transmission/reflection array antenna that can switch the maximum radiation direction.In this thesis,a reconfigurable frequency selective surface with pass-stop band switching is designed.By adding a phase modulation unit on the upper layer of the reconfigurable frequency selective surface,the units are reasonably arranged to control the phase of the incident wave,and the Vivaldi antenna is selected as the feed source,designed a transmission/reflection array antenna.The antenna has the characteristics of high gain,and the switching of the transmission and reflection states is controlled by controlling the on and off of the diode,thereby realizing the transformation of the maximum radiation direction.