Research On Technologies Of Wideband Antennas Based On Complex Platforms

Modern warfare is a high-tech and multi-information fusion war,the performance requirements of various weapon platforms are constantly improved,and the functional requirements are gradually diversified,such as communication,navigation,electronic reconnaissance countermeasures and situational awareness,and so on.However,these functional systems not only occupy the larger volume and load of the platform,but also affect the electromagnetic stealth,electromagnetic compatibility,and aerodynamics characteristics of the whole system.With the rapid development of science and technology,people begin to consider integrated electronic information system,and one of its representative technologies is the RF aperture synthesis.The main methods to realize RF aperture synthesis are as follows: one is broadband antenna or multi-functional phased array antenna,the other is conformal or embedded antenna.Although there are many kinds of directional wideband antennas,they still have some shortcomings to be improved.For examples,the antenna gain fluctuates greatly within the operating band,and the axial ratio(AR)bandwidth is smaller than the impedance bandwidth.The dissertation focuses on the computational method of the broadband electromagnetic problem,wideband antenna and wideband array antenna,a series of researches are carried out.The main work and innovations are summarized as follows:1.The research of the computational method of broadband electromagnetic problem.The discontinuous Galerkin time domain method(DGTD),which is a new time domain numerical method for computational electromagnetics,is studied systematically.First,we deeply studied the DGTD method including the basic principle of the method,the realization of various boundary conditions,and the introduction of the excitation source in the calculation of electromagnetic scattering and radiation problems.For the multiscale electromagnetic problem,due to the simple and easy parallelism of explicit time integral method,the DGTD method based on leap-frog explicit scheme is studied in this dissertation.However,the global time step of the explicit scheme is limited by the minimum grid element,so the computational efficiency is severely restricted.To overcome this problem,a leap-frog recursive local time-stepping scheme is studied deeply,and an improved local time-stepping algorithm is proposed.The improved local time-stepping algorithm not only maintains the advantages of the Montseny recursive local time-stepping scheme,such as intuitive principle and simple programming,but also significantly improves the computational efficiency of the DGTD method.Several electromagnetic scattering and radiation examples show that the computational efficiency of the proposed algorithm is greatly improved.Importantly,there is no additional storage requirement.2.The research on wideband antenna based on complex carrier.For traditional wideband antennas,such as dipole antennas and conical antennas,due to the bidirectional radiation characteristics,a reflected plate is needed at a specific height to form directional radiation.Because of the height related to the frequency,the gain and radiation patterns of the antennas is unstable and unsymmetrical within the operating band.Although many techniques are proposed to improve the radiation characteristics,also increase the difficulty of the antenna design and manufacture.A new complementary antenna named magnetoelectric(ME)dipole antenna is deeply studied.Firstly,a wideband ME dipole antenna with microstrip line aperture-coupled excitation is proposed.This design not only maintains the advantages of the traditional ME dipole antenna,but also significantly enhances the impedance bandwidth.Based on the same feed structure,a circularly polarized ME dipole antenna is designed.The AR bandwidth of the antenna is the same as the impedance bandwidth,and the gain fluctuation is small in the AR bandwidth.Secondly,in order to suppress the backward radiation,a ME dipole antenna based on the stripline aperture-coupled excitation is proposed,which successfully suppressed the backward radiation and improved the front-to-back ratio.In addition,the influence of different aperture cavities on the electrical performance of wideband ME dipole antenna is studied.Through the analysis of the influence mechanism of the cavities on the antenna performance,the design method of high performance cavity is mastered.Finally,based on the designed high performance cavity,the influence of complex carrier on the electrical performance of wideband ME dipole antenna is deeply studied and discussed.3.The research on wideband array antenna.Based on the concept of tightly coupled and the ME dipole antenna proposed in the second point,a wideband array antenna based on microstrip line aperture-coupled excitation is proposed.The tightly coupled array antenna adopts the microstrip line aperture-coupled feed structure,which eliminates the broadband balun design of the traditional tightly coupled dipole array antenna,and greatly simplifies the design difficulty of the tightly coupled array antenna.The proposed array antenna has the advantages of compact structure,simple feed and low profile.The simulation results of infinite array unit cell show that when scanning to ±45° in all azimuth planes,an impedance bandwidth of active VSWR < 2 can be achieved about 86%,ranging from 2.55 GHz to 6.4GHz.Then,the edge truncation effect,the dielectric superstrate and the frequency selective surface superatrate of the tightly coupled finite array are studied and discussed.Finally,in order to verify the proposal,a 9 × 9 finite wideband tightly coupled array antenna is fabricated and measured.The experimental results are in good agreement with the simulation results.