| In order to use the existing spectrum resources efficiently in an increasingly complex electromagnetic environment,increase the communication capacity of the system,avoid interference between adjacent channels,and achieve the most reasonable use of the electromagnetic spectrum,this dissertation delves into a variety of multi-band,broadband,and miniaturized radio frequency(RF)components that implement efficient electromagnetic control for different scenarios.This dissertation focuses on two aspects:electromagnetic radiation and electromagnetic transformation.In terms of electromagnetic radiation,by studying multi-polarized antennas and multi-passband microstrip filters,we explore the RF components with high performance for electromagnetic control.In terms of electromagnetic transformation,based on electromagnetic metamaterials,exploratory research has been conducted on the mechanism and method of the arbitrary control of spatial electromagnetic waves.The main research contents and results of the thesis include:1.Aiming at the control of indoor electromagnetic wave radiation,a high-gain compact dual-polarization dual-frequency omnidirectional antenna was studied in depth.Based on the method of slot resonator edge excitation,a dual-rotation bandwidth compensation network was introduced to·expand the bandwidth of the antenna radiating unit,and a four-way broadband feeding network was designed to feed the upper and lower two dipole radiating units simultaneously.Among them,eight parasitic patches on the upper part of the antenna enhance the bandwidth of the upper frequency and four patches between adjacent dipoles on the lower part of the antenna reduce gain fluctuations and cross polarization.2.Aiming at the dual-wide coverage of the fifth-generation(5G)mobile communication base station antennas and the characteristics of omnidirectional communication between cars,a tri-polarized antenna composed of a single dipole antenna and a differential dual-polarized antenna unit was proposed.By arranging eight pairs of inverted L-shaped patches of different sizes around the dual-polarized antenna unit,the half-power-beam width(HPBW)in the E-plane and H-plane is extended to nearly 180° in the 5G frequency band,which enhances the coverage of the directional dual-polarized antenna,while increasing the horizontal gain of the omnidirectional dipole.A pair of symmetrical differential circuits are used to feed the dual-polarized dipoles to improve the port isolation of the dual-polarized dipole antennas and to stabilize the gain fluctuations of the single-polarized omnidirectional antenna.3.Aiming at the electromagnetic wave control in the lumped parameter device,a filter for frequency selective regulation of the electromagnetic wave signal was studied.A three-band four-mode microstrip band-pass filter with ultra-high frequency selection characteristics is proposed by means of folding branch-loaded resonators.The introduction of an embedded open-circuit feeder structure produces multiple transmission zeros,which eliminates the harmonic passband and widens the upper stopband.The equivalent circuit model and parity mode theory are used to deeply analyze the evolution process and working mechanism of the four modes,which proves that each resonance mode has independent tuning capabilities for the resonance frequency and bandwidth.4.Aiming at the electromagnetic wave diffraction and frequency selective isolation of anti-detection in the airspace,a metamaterial-based"electromagnetic diffraction cloaking" and a frequency selective surface were studied.In view of the weak penetration and diffraction ability of high-frequency signals,in order to enhance the coverage of wireless signals,a metamaterial-based "electromagnetic diffraction cloaking" is proposed.By constructing an artificial structure with gradient electromagnetic parameters,the spatial propagation path of incident electromagnetic waves can be freely steered to achieve the diffraction of electromagnetic waves.Finally,tensor transmission line units are used to provide a physically implementable method for these anisotropic units,and the relationship between electromagnetic parameters and lumped circuit parameters is deduced.In addition,in order to protect the privacy of indoor communications,a frequency-selective surface that enhances privacy protection is proposed to selectively suppress the wireless location area network(WLAN)signals to be protected.At the same time,this application isolates electromagnetic space and expands the frequency spectrum. |
