Design Of Multilayer Dual-band Arrays Based On Spiral Structures And Phase Delay Line Loading

In the future 5G communications,the millimeter-wave band has become the mainstream of development and application due to its abundant spectrum resources,wide available bandwidth,and extremely high data transmission rate.In recent years,many scholars have also begun to research 5G antennas operating in the millimeter waves.In 5G base stations,high gain antennas are generally required to compensate for the loss of high frequency communications during propagation.Microstrip planar reflectarrays and transmitarrays,as the first choice of new high-gain antennas,have the advantages of simple structure,light w eight,no complex feed network,low processing cost,etc.,which has attracted extensive attention of researchers in the world.For this technology,the main research work of the dissertation focuses on reducing the degree of electromagnetic coupling between the dual-band reflectarrays and the reflectarray/transmitarray,making the dual-band work independently,and ultimately obtaining more flexible angle controllability and high gain.This paper systematically summarizes the phase adjustment of the dual-band reflection cell using three different combinations,namely,the combination adjustment of the key cell sizes,the combination adjustment of the rotation angle and the cell size,and the combination adjustment of the rotation angle and the phase delay line loading.By comparing the degree of elimination of the electromagnetic coupling between the three methods,the paper puts forward the research ideas and technical routes.Based on comprehensive research analysis and theoretical exploration,the paper focuses on dual-band reflectarrays and transmitarrays as follows:Firstly,two 20/30 GHz multilayer dual-band circularly polarized reflectarrays based on FSS(Frequency Selective Surface)with a double-ring structure are designed.When both high and low frequency cell use Phoenix cells,a large amount of simulation time is required to reduce the coupling between the cells.Therefore,a double symmetrical C-shaped rings with a controllable rotation angle is used as a high-frequency cell,and a Phoenix cell,an improved Malta cell,a four-arm Archimedes spiral cell are used as low-frequency cells,respectively.The phase shift responses between the high and low frequency cells are orthogonal to each other,so that the electromagnetic coupling between the two bands is almost completely eliminated.The design of dual-band cell successfully simplifies into two designs of single-band cell,greatly reducing design complexity.Finally,a 15x15 array is designed using a combination of a double symmetrical C-shaped rings with controllable rotation angles and an improved Malta cell.At 20 GHz and 30 GHz,the simulation results show that the gains are 20.38 dB and 25.1 dB,respectively.In addition,a 18×18 array is designed using a combination of a double symmetrical C-shaped rings with controllable rotation angles and four-arm Archimedean spiral cel.At 20 GHz and 30 GHz,the simulation gains are 19.7 dB and 26.8 dB respectively.At the high and low bands,the 1-dB gain bandwidth are 15%and 7.5%,respectively.Secondly,based on phase shift response orthogonalization of dual-band reflection cells,two Ka/Ku-band multilayer circularly polarized reflectarrays/transmitarrays based on FSS are designed.Both of them are 15×15 in the aperture size.FSS uses hollow cross-shaped embedded cross dipole patch structure.A double symmetrical C-shaped rings with controllable rotation angles and a four-layer square slots are used as high-frequency reflection cell and low-frequency transmission cell,respectively.When the array is operating in the reflective mode,the simulation gains are 22.78 dB,23.82 dB,and 23.07 dB at 19 GHz,20 GHz,and 21 GHz,respectively.When the array is operating in transmission mode,the simulation gains are 20.26 dB and 18.84 dB at 12.25 GHz and 13.5 GHz,respectively.Then a double symmetrical C-shaped rings with controllable rotation angles and four-layer square rings with opening diagonal cross dipole cell are used as high-frequency reflection cell and low-frequency transmission cell,respectively.When the array works in reflective mode,the simulated gain is 23.72 dB at 20 GHz,and 1-dB gain bandwidth is 6.25%.When the array is operating in transmission mode,the gain is 19.85 dB at 13.5 GHz,and the 1-dB gain bandwidth is 7.4%.