Research On The Generation And Regulation Mechanism Of Vortex Electromagnetic Wave Based On Helical Antenna

With the development of wireless communication,vortex waves have gradually entered people's field of vision.Since orbital angular momentum was discovered in optics,optical orbital angular momentum has been widely used in optical communication.With the popularity of orbital angular momentum in the field of optics,it has also been applied to the field of radio frequency,and the concept of vortex electromagnetic waves has been proposed.Due to the infinity of vortex electromagnetic wave modes and the orthogonality between modes,it can be used in signal multiplexing,and the spectral efficiency and communication capability can be greatly improved.Therefore,designing antennas that generate vortex electromagnetic waves has become one of the research hotspots.However,the degree of freedom and complexity of vortex electromagnetic waves are not high at this stage,and the degree of modal utilization is not high.Therefore,the thesis starts with helical antennas and designs two helical antennas for generating vortex electromagnetic waves.The thesis starts with the helical antenna and designs two helical antennas for generating vortex electromagnetic waves.The main work and contributions of this thesis can be summarized as:1.The formula deduces the principle of generating vortex electromagnetic waves by a single-armed helical antenna.Using this principle,a single-armed helical antenna is designed to generate integer-order and fractional-order orbital angular momentum.At the same time,the basic principle of impedance matching is expounded.The optimization is carried out in HFSS,and the current distribution diagram,standing wave ratio,E-plane and H-plane pattern and field distribution of the antenna are obtained.The purity of the vortex electromagnetic wave is calculated,and the simulation of the purity is carried out in MATLAB.The simulation results show that the radiated beam has the characteristics of integer order and fractional order,which confirms that the single-arm helical antenna can generate integer order and fractional order orbital angular momentum.The antenna was fabricated,and the performance of the antenna in practice was tested.The test results were basically consistent with the simulation results.2.The formula deduces the principle of the double-armed helical antenna generating vortex electromagnetic waves.Using this principle,a double-armed helical antenna is designed,which can be used to simultaneously generate multiple modal superimposed vortex electromagnetic waves at a single frequency.The modes are equally spaced,forming a comb-like modal spectrum.We analyzed the feeding of the antenna,designed a double-arm helical antenna based on the feeding network,analyzed the current distribution,standing wave ratio and field distribution of the antenna by using HFSS,and simulated the vortex generated by the antenna in MATLAB.The mode purity of the vortex electromagnetic wave verifies that the antenna can generate a vortex electromagnetic wave with multiple modes superimposed.Then change the pitch of the antenna and analyze the change of the mode purity of the vortex electromagnetic wave.The results show that when the pitch is suitable,the double-arm three-dimensional helical antenna can simultaneously generate multiple modal superimposed vortex electromagnetic waves at a single frequency point.We also explored the influence of the position of the observation plane on the test results of the mode purity of the vortex electromagnetic wave.The analysis results show that the deviation of the position of the observation plane will bring test errors to the test of the mode purity of the vortex wave.Therefore,when the purity test is carried out.The interference of the deviation of the observation plane position on the antenna test cannot be ignored,and try to ensure that the position of the observation plane is aligned with the antenna.