Research On Artificial Electromagnetic Structures In Multi-Band Miniaturized And Frequency Beam-Scanning Antennas

Artificial electromagnetic structures are a kind of artificial composite structures composed of subwavelength elements arranged in order,which has a series of extraordinary physical properties and has attracted great attention in many research fields.Using the excellent electromagnetic characteristics of artificial electromagnetic structures to design and improve the microwave antennas is an important direction of the application of artificial electromagnetic structure in microwave field,and has become a research hotspot with important research value and broad development prospects.Focusing on the application of artificial electromagnetic structures in microwave antennas,combined with the difficult and key problems faced by multiband miniaturized and frequency beam-scanning antennas,a series of innovative researches have been carried out by this dissertation using the methods of theoretical derivation,simulation and experimental verification.The main contents are as follows:1.Two multi-band miniaturized antennas for WLAN and WiMAX applications are proposed.Firstly,a new triple-band miniaturized antenna with simple structure is designed.The radiation structure of this antenna is only composed of two simple monopole radiating elements,which provides a new way to simplify the structural complexity of the multi-band miniaturized antenna.Secondly,a triple-band miniaturized antenna based on a new design method combining the multi-resonant artificial electromagnetic structure unit and the split-ring defected ground structure is proposed.This antenna achieves a high level of miniaturization under the condition of achieving good input and radiation performance,and realizes the effective fusion of multiband and miniaturization design methods.The experimental results show that this two antennas can cover all operating frequency bands required by WLAN and WiMAX appications well,and have good gain and stable omnidirectional radiation characteristics in three operating frequency bands.2.A frequency beam-scanning antenna with high frequency-scanning sensitivity is proposed.Firstly,a new composite slow-wave waveguide based on spoof surface plasmon polaritons and substrate integrated waveguide is designed.On this basis,a novel periodic digital modulation method based on staggered distribution of metallized vias is proposed and used to modulate the composite slow-wave waveguide,realizing frequency beam-scanning antenna with high frequency-scanning sensitivity.The experimental results confirm that the frequencyscanning sensitivity of this antenna is as high as 9.8°/100 MHz,and the stable unidirectional radiation characteristic is also achieved in the working frequency band.3.A compact and wide scanning-angle frequency beam-scanning antenna with open stopband suppression is proposed.A novel miniaturized composite waveguide is designed by introducing the double-layer spoof surface plasmon polaritons guided-wave structures into the half-mode substrate integrated waveguide.Furthermore,a new double-layer asymmetric periodic modulation method is proposed and used to modulate the composite waveguide to design the frequency beam-scanning antenna.This modulation method can effectively suppress the open stop-band problem common to the periodic beam-scanning antennas.This antenna utilizes a novel design method combining half-mode substrate integrated waveguide and spoof surface plasmon polaritons,and achieves a very compact size.The experimental results show that this antenna achieves continuous unidirectional beam-scanning from backward to forward with a wide scanning-angle of 125°,and the open stop-band problem is well suppressed around the broadside radiation direction.4.A miniaturized frequency beam-scanning antenna with open stop-band suppression and flexible design of beam-scanning range is proposed.Firstly,the combination of a spoof surface plasmon polaritons and folded half-mode substrate integrated waveguide is realized for the first time,and thus a novel compact composite slow-wave waveguide is designed.Based on this,a single-layer periodic modulation method is proposed to efficiently modulate the composite slow-wave waveguide,and the folded half-mode substrate integrated waveguide is used for the first time to realize the frequency beam-scanning antenna.This antenna has a very small lateral width and the range of beam-scanning can be flexibly designed without changing the modulation structure.Experimental results show that this antenna achieves stable unidirectional beam-scanning from backward to forward continuously,and eliminates the open stop-band problem around the broadside radiation direction successfully.Notably,this antenna owns a smaller lateral width than the existing similar planar frequency beam-scanning antennas.5.A simple low-profile circularly polarized frequency beam-scanning antenna is proposed.Firstly,a novel slow-wave transmission line based on slotline and tilted spoof surface plasmon polaritons guided-wave structures is designed,which can provide orthogonal electric-field distributions in the same cross-section orthogonal to the propagation direction.Furthermore,in order to realize the characteristics of circular polarization and frequency beam-scanning,a simple bilateral tilted asymmetric periodic modulation method is proposed to modulate the slow-wave transmission line.The proposed antenna has simple structure and low profile.Experimental and simulation results show that this antenna achieves good right-handed and left-handed circularly polarized scanning beam in the upper and lower half spaces,respectively.