Research On The Design Technology Of Vortex Electromagnetic Wave Antenna Based On Reflective Metasurface

The vortex electromagnetic wave mode multiplexing,as a novel space division multiplexing technique,is a research hotspot for highcapacity wireless communications.Reflective metasurface demonstrate outstanding superiority in the flexible modulation of amplitude,phase and polarisation of electromagnetic waves and are commonly used in the generation of vortex electromagnetic waves.Therefore,the technical research of reflective metasurface in vortex electromagnetic wave antennas is of great academic value and practical significance.The main research content and technological innovation points of this thesis include.1.To address the narrow-band problem of the vortex electromagnetic wave reflectarray,an I-shaped element with an embedded open ring is designed.The element achieves multiresonant broadband performance with a bandwidth of up to 75.2%(18.32-40.42 GHz)by introducing multiple current coupling paths.The design of the broadband circularly polarized reflectarray antenna is completed based on the element’s rotation-controlled phase technique,with a maximum vortex electromagnetic wave modal purity of 94%and a frequency coverage of 20-40 GHz(66.6%)for modal purity greater than 85%.2.To address the beam divergence problem of vortex electromagnetic waves,an arc-loaded I-shaped element is proposed,a phase compensation calculation method for the line polarization incidence case is derived and a 15 λ0×15 λ0 broadband high-order Bessel reflectarray design is realized.The beamwidth distance of the designed non-diffracting reflectarray at a non-diffracting distance of 70 λ0 is reduced by 5.4 λ0(@30 GHz)compared to conventional vortex reflectarray of the same aperture,effectively reducing the beam divergence angle.Finally,the reflectarray was processed and tested to successfully produce non-diffracting OAM beam carrying+2 mode in the 24-38 GHz(45.2%)frequency band.3.A multibeam multimodal vortex reflectarray antenna is designed based on the aperture field superposition method for a single-beam antenna limiting the modal multiplexing of vortex electromagnetic waves.The feeder is a circularly polarized horn loaded with a dovetail substrate with an axial ratio bandwidth of 53.6%(23.61-40.91 GHz).The reflectarray consists of 20×20 mirrored M-shaped cells capable of generating four simultaneous vortex electromagnetic beams in a wide bandwidth of 28-37 GHz(27.7%)with beam directions of(θ=20,φ=0°),(θ=30°,φ=90°),(θ=20°,φ=180°),and(θ=30°,φ=270°),corresponding to mode numbers of l=+1,l=+2,l=-1,and l=-2 respectively.4.To address the problem that most antennas cannot achieve arbitrary generation and switching of vortex electromagnetic waves,a four-slotted patch element based on diode loading is designed,and the 90°polarity conversion of the element is achieved by controlling the switching states of two diodes on the patch.Based on the 1-bit phase quantization principle,the design of a 1-bit programmable vortex electromagnetic wave super-surface antenna array is completed.The reflectarray consists of 15×15 elements,and by adjusting the switching states of the diodes,vortex electromagnetic waves with different modes such as l＝0,±1 and ±2 can be generated in the 11.5～13.5 GHz(16.0%)frequency band.