OAM mode purity improvement based on antenna array

Orbital Angular Momentum(OAM)waves are characterized by helical wave fronts and orthogonality between different modes.Therefore,OAM waves have huge potential in improving wireless communications'channel capacity and radar imaging's resolution.Consequently,the generation and application of OAM waves have attracted a lot of attention.And many methods are proposed to generate OAM waves.Although antenna array is the most popular method of generating OAM waves,OAM waves generated by antenna array have redundant modes.However,all advantages of OAM waves are closely related to infinite OAM modes.Thus,to better apply OAM waves to wireless communications and radar,it is very important to reduce unnecessary OAM modes and improve the OAM mode purity.In order to improve the OAM mode purity,two combined antenna arrays composed of X direction antenna and Y direction antenna array are proposed in this paper.The X direction antenna array and the Y direction antenna array are supplied by the excitations with the same amplitude and fixed phase shift.The overall phase shift of the X direction antenna array isπ/2 more or less than that of the Y direction antenna array.The results of formulas and antenna models in CST show that the combined antenna arrays can generate OAM waves with less redundant modes in x component,y component and z component.Besides,the z component carries pure OAM modes.

Theoretical analysis and comparison of OAM waves generated by three kinds of antenna array

Antenna array is one of the methods which can generate Orbital Angular Momentum(OAM)waves.However,OAM waves generated by different antenna arrays have different characteristics of Electric-field(E-field)com-ponents'distribution and radiation patterns.In order to solve this problem,we derive E-feld formulas of OAM waves generated by different kinds of dipole antenna array in this paper.The dipole antenna arrays are arranged by three methods:1)antenna elements are in the same direction of y axis,2)antenna elements are in the radial direction and 3)antenna elements are in the azimuthal direction.Results show that x components,y components and z components carry different OAM modes under the three conditions.Simulation results show that the same direction antenna array produces the best OAM waves because the y component is dominated by OAM mode l and RHCP/LHCP waves are negligible in energy,while the pure OAM waves carried by the z components generated by the other two antenna arrays have little energy.In addition,only the radiation pattern ofl=0 produced by the same direction antenna array does not have a null zone in the propagation direction.Radiation patterns of l=±1 do not have null zones in the propagation direction generated by other two antenna arrays.

GRINDING FORCE IN PRECISION MACHINING OF WC-Co COATING BY CUP WHEEL

High machining precision and machining efficiency can be obtained in grinding WC-Co coating by cup wheel. The conventional model of the grinding force is not suitable for the grinding of the cup wheel due to the difference in grinding style between the cup wheel and the conventional external wheel. So the grit grinding process of the cup wheel is studied, and a new concept of the effective grinding width of the cup wheel is presented. Then the grinding force in grinding WC-Co coating materials by cup wheel is analyzed and a theoretical formula is deduced. Finally, experimental results of the grinding force verify the correctness and the precision of the theoretical formula.