Directional Enhancement Design Of Horn Array

The traditional horn antenna is the most classic,simplest microwave antenna and its design ideal is the most mature.Many of the performance of the horn antenna can be improved by loading structures on the horn antenna.In this paper,the loading structures of horn array are optimized.Meantime,the array directionality as the main indicator,and the loading structure as the main method are considered.The main research work is as follows:The array directivity of different cell dimensions is compared for the same array area.Different array gains are not much different.Elements with smaler cell dimensions are easier to control in phase and amplitude.And its size that perpendicular to the caliber surface is smaler than others.Therefore,horn antennas which cell dimension is less than 1.5 lambda are the main design objects.First,with the principle of Yagi antenna,the directional device which is loaded above the horn antenna is studied.The influence of loading is analyzed.The parameters of the length and adjacent spacing of the deflector are designed as well.The electric field radiation changes after loading are analyzed.After loaded,the gain of element and the four-element array at the center frequency is increased by 4.75 dB and 2.72 dB.Then,two metamaterial structures were designed based on the phase compensation principle.The phase difference to the phase center is calculated,and the basic principle of phase compensation is analyzed.If the phase of the electric field on the upper surface of the metamaterial is consistent,the gain of antenna will be improved.The basic element of the first metamaterial is a rectangular dielectric block.A cylindrical hole is drilled in it to simulate different electromagnetic parameters and phase.Those of that are placed on the designed plane following the previous calculation.The larger the size of the hole that is dug,the greater the equivalent phase difference.After loading the structure,the gain at the center frequency is increased by 0.5 dB.Using the conclusions of the previous design,the concentric annular structure is designed to achieve a more uniform electric field phase distribution on the metamaterial surface.The metamaterial structure has better phase compensation effect in a wider frequency band by designing the concentric cylinder width and the hole slit.The element's average gain increased by 2.99 dB from 13 to 17 GHz and the gain at the center frequency increased by 3.27 dB after loading.After composing a four-element array,the gain of the center frequency is increased by 1.82 dB.Thus,the second metamaterials structure is better than the first.A zero-refraction-index material was designed.The gain of element with large-caliber is increased by 2.45 dB after loading it.The array gain is increased by 1.64 dB and the grating gate level is suppressed after loading it.After that,the two structures were compared.Then,the coupling between adjacent elements is analyzed.Based on the principle of isolation and decoupling,a metal strip structure is designed.When the metal strip structure is loaded,the radiation gain is increased by 1 dB.And while the metal baffle structure can only be increased by 0.2 dB.Finally,based on the principle of the direction product,the radiation patterns of several simple rule arrays are calculated and compared.The circular boundary array has the highest gain in the case the number of cells is similar and the spacing between adjacent elements is the same.The simulation results show that the grating lobes have the best suppression effect when the array row or column offset is 0.6 times.