| The radome is a shell structure that protects the antenna or array antenna inside from the complex natural environment outside.Due to the ground radar antenna systems are generally large-scale,they are mostly located in areas with open and flat environments,such as mountain tops,deserts,and coasts.However,the harsh environmental conditions have extremely effects on the service life and use effect of the radar antenna systems which makes it particularly important to set up a ground radome.The ground radome can ensure that the radar antenna systems work free from environmental interference and maintain normal and continuous working conditions.The common ground radomes are mostly spherical,and their impact on the antennas inside is small and easy to analyze.In this thesis,the electromagnetic characteristics of a large ground radome will be simulated and analyzed.Different from the spherical radome,this ground radome is larger in size and more complex in structure,and there are few researches on ground radome with this structure.Therefore,how to establish an electromagnetic model integrating array antennas and the large ground radome,and how to quickly and accurately simulate the far-field pattern are very important.And then need to study the change of the gain pattern before and after the array antennas mounted in the radome.Aiming at the problem of how to fast and accurate simulate the integrated model,the simulation is carried out using HOMo M hybridized with MLFMA.This is because antennas contain a lot of small structures and the ground radome has a large electrical size,which makes it difficult to perform accurate and efficient simulation with a single algorithm.The influence of the large ground radome on the radiaiton characteristics of array antennas is studied based on the HOMo M-MLFMA and the high-performance computer cluster of Xi Dian university.Firstly,an array antenna model is constructed and simulated to obtain its far-field radiation pattern.Then,an electromagnetic model integrating the array antenna and the large ground radome is established and the simulation is carried out using the HOMo M-MLFMA to obtain its far-field pattern.By comparing the radiation pattern of the array antenna before and after mounting in the radome,the influence of the large ground radome on the radiaiton characteristics is analyzed.The main lobe direction of the array antenna is changed by scanning to analyze the effect of the radome on the array antenna at different angles.Through the comprehensive analysis of the dipole array antenna and the microstrip array antenna before and after mounting in the radome,the influence regulars of the large ground radome on array antennas are summarized.Firstly,the setup of the ground radome will cause the lobe fluctuation of the E-plane pattern and the side lobe rise of the H-plane pattern.But the beam width and side lobe level of array antennas are basically unaffected.Secondly,when the lobe width is wider and the scanning angle is narrower,the main lobe direction of the array antenna after mounting in the radome will not deflect.With the scanning angle increases,the deflection in the direction of the main lobe becomes more obviously.And then analysis with the structure of the radome,it was found that the metal frame weakened the antenna gain more obviously.When the direction of the main lobe points to these angles,it will happen that the maximum gain is not at the direction of the main lobe.At other angles,due to the superposition of the electric field of radiation field and scattering field,the gain of the array antenna will increase. |
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