Research On The Integrative Elecmagnetic Modeling And The Engineering Practice For Antennas And Platforms

More and more antennas are being mounted on weapon platforms for multifunction, and armament systems become more complex. The mutual couplings between the antennas and the platform affect not only the parameters of the former but also the other characteristics of the whole system including electromagnetic compatibility, low observability, and aerodynamics, etc. Hence, the importance of the integrative platform-antenna modeling and analyzing gets more evident. In actual engineering, to decrease the platform load and the antenna number, efficient wideband/ultra-wideband antennas have been put on an important position; in addition, co-aperture or conformal studies for onboard antennas have also been recorded in calendar.The work in this paper is carried out based on the above mentioned backgrounds; its content includes some integrative electromagnetic modeling techniques and also some engineering designs according to urgent requirements. The involved methods include rigorous integral equation methods, high efficient combined/approximate algorithms, experimental testing and scale model methods, etc.Surrounding the integrative numerical modeling, this paper firstly takes the moment methods as a foundation. The main process of this approach is shown, some key techniques are analyzed, and several examples of antennas mounted on electrically small or resonant platforms are given out. When emphasis focused on the details of the geometrical/electromagnetic modeling of the antenna feed regions, two new-typed wires-to-surface and pyramid-to-surface/pyramid junction bases are presented, which enjoys the benefits of decreasing unknowns and accelerating solving speed.To improve computational efficiency, the hybrid electromagnetic iterative methods and the fast multipole method (or multilevel fast multipole algorithm, MLFMA) are further studied. These two categories of methods, are accurate and high efficient. For the MLFMA, its detailed process in the modeling for problems of antennas mounted on electrically large PEC objects and also its applications in dielectric-metal combined platforms are studied in this paper. All the examples for demonstration are pertinent.Platform-antenna problems have distinct characteristics, namely the localized or restricted features. Some hybrid or approximate methods based on these characteristics can be adopted to save computational cost and increase solving efficiency. In this paper, the emphases are mainly put on the truncations of the far ends of the platforms, the hybrid moments-physical optics methods in which the mutual couplings between the elements of the middle/far regions of the platforms are ignored, the applications of the new-typed phase-extracted basis functions in radiation problems, and the modification to the Green's function by plane-wave reflection coefficients when considering the effects of lossy grounds. The efficiencies of these methods are well confirmed by the comparisons between their results with those obtained through accurate methods.The design of the shipboard shortwave/ultrashort ultra-wideband communication antenna in this paper is an important engineering practice based on experiment methods. With the aid of some existing wideband techniques, a new-typed dual-feed combined cage/cone-shaped ultra-wideband antenna for shipboard omnidirectional communication has been designd successfully though the integration of structure combining, dual-port feeding, sleeve matching, and distributed parameter optimizing. The proporsed antenna has a good impedance match in a bandwidth larger than 4.9 octaves, and its geometrical dimensions are much smaller than those of the internal/external congeneric ones, so it is more preponderant in practicality.Two very challenging co-aperture arrangements of dual antennas for orientation plus telemetry or orientation plus fuze are proposed under actual missile-board dielectric radomes in this paper. A traditional quadrifilar helix is improved to act as the orientation antenna, a single monopole or a two-element array mounted on a ring-shaped ground are adopted to suit the telemetry role, while the fuze antenna is simply made of a horizontal monopole threaded out of the inner wall of the cavity. The effects of the aperture dimensions and the mutual couplings on the antenna performances are analized through a large number of experiments. A right-hand circular polarized radiation normal to the aperture surface for the orientation antenna, a radiation in the grazing direction of the aperture surface for the telemetry antenna, and a linear polarized radiation normal to the aperture for the fuze antenna are simultaneously and well realized in the final arrangements, and the bandwidth requirements for these antennas are also met.Although the work might be some superficial, it has formed a rough profile about the integrative modeling and the experimental investigating methods for platform-antenna problems. At the same time, it has formed the capability to analize radiation problems of antennas on electrically large and complex platforms and also formed a good base for future studies. The two engineering designs both have good electric performances and application foregrounds and are being put forward with great efforts.