Research On Beam Scanning Technology Based On Electrically Adjustable Frequency Selective Surface

The Frequency Selective Surface(FSS)is usually a periodic structure consisting of a metal surface gap or a metal surface patch on a medium surface arranged in a certain manner.The electromagnetic wave with different polarization,frequency or incident angle can be selectively reflected or transmitted,and its effect is essentially equivalent to a filter in space.The frequency selective surface for loading active electronic components such as PIN tubes or varactors is called active FSS,and its resonant characteristics can be varied by adjusting the bias voltage and current of the loaded device.Frequency selective surfaces have been widely used in spatial filters,reflective surfaces,polarization conversion,and radar scattering cross-section reduction,and are increasingly being used in other fields.It is also used in reconfigurable antennas due to its specific performance.The reconfigurable pattern is mainly achieved by changing the current distribution of the antenna surface to achieve beam tunability.The pattern reconfigurable antenna has the advantages of being applicable to a complex electromagnetic environment,being capable of maneuvering to prevent electromagnetic interference,improving system reliability,and saving input energy.This paper first briefly introduces the basic theory of FSS and its related applications,designs a pattern reconfigurable antenna based on the electrically tunable frequency selection surface at 2.4 GHz,and designs a Ka-band based FSS.The reconfigurable transmission array antenna is modified and improved.The specific research contents of this paper are as follows:First of all,this paper designs a FSS-based pattern reconfigurable antenna at 2.4GHz.The antenna consists of a FSS-based pattern reconfigurable structure and a microstrip patch antenna.The microstrip patch antenna is used as a feed and adopts a side feed mode with a maximum gain of 7.8 d B and a main beam direction of 0°.The pattern-reconfigurable structure based on the frequency selection surface consists of a 4×4 FSS unit.The frequencyselective surface filtering characteristics of the surface and the forward and reverse cut-off characteristics of the PIN diode are used to realize the antenna pattern in the upper half.Beam scanning in space.The specific performance is that when the working state of the diode is switched,the three states of the antenna pattern in the half space can be changed.The deflection angles of the beam are 0°,-35° and +35°,respectively,and the maximum gain is 8.9d B,8.4d B and 8.3d B.In order to verify the performance of the antenna,we processed and tested it.The results show that the actual measurement and simulation are basically consistent and meet the design requirements.Secondly,this paper designs a Ka-band FSS-based pattern reconfigurable microstrip transmission array antenna.The antenna unit structure is constructed by three layers of metal printed on two identical dielectric substrates.The three layers of metal are respectively defined as a receiving layer,a ground layer,and an emitting layer;and the other media are bonded between the two dielectric plates.The receiving layer and the emitting layer are connected by metal through holes.The receiving layer structure is obtained by etching a letter "N" on the metal wafer,and the structure of the emitting layer is the same as that of the receiving layer.When the receiving layer is in the same direction as the portion where the emissive layer is etched,the electromagnetic wave exhibits good wave transmission characteristics at a frequency of 30.2 GHz to 33.2 GHz;when the receiving layer is opposite to the etched portion of the emissive layer,the electromagnetic wave is at a frequency of 30 GHz to 34 GHz.It exhibits good wave-transmission characteristics,and the phase difference between the two transmissions is close to 180°.Three 11×11=121 arrays were designed by arranging and combining the unit structures.The structure of the array and the effect of the array on the antenna pattern are detailed in the text.The feed uses a Ka-band standard horn,and the direction of electromagnetic wave radiation is normal incidence.The simulation is carried out by CST electromagnetic simulation software.The results show that the microstrip transmission array can realize the reconfigurable antenna pattern.Finally,on the basis of the microstrip transmission array,the dielectric substrate material is replaced,the structure of the receiving layer and the emissive layer of the unit is improved,and a square metal patch is filled at the four corners of the "N"-shaped etching of the metal wafer,and a design is obtained.The Ka-band based micro-band transmission array of the frequency selective surface,and then the emission layer metal patch is rotated by 180° to obtain a cell structure of two states.In the two states,the phase difference of the transmission coefficient of the unit structure is 180°.On the basis of this,a standard horn and a pair of Vivaldi are used as feeds to form an array of 11×11=121,and three different arrangement combinations are obtained.Co-simulation between HFSS and CST shows that the frequency selective surface achieves the beam reconfigurable function.