Research Of Electromagnetic Field Distribution Characteristic In Complex Ship Environment

Ships are complex platforms having many antenna connected communication and radio navigation systems. The electromagnetic environment of a warship is a reasonably complex one involving the communication systems (receiver, transmitter) covering a frequency range of a few kHz to 40 GHz. Numerous studies have been issued in the literature dealing with the analysis of the antennas mounted on a large complex structure in recent years. In the case of a shipboard antenna configuration, computing the effect of metal constructions (funnel, mast, etc) on the performance of the antennas, consequently on the characteristics of shipboard EMC, is particularly complicated. Numerical modeling for the radiation patterns and mutual coupling between them offers critical information of designing and positioning the antennas. Various theoretical methods, such as diffraction theory, mutual coupling, are used for the evaluation of the interaction of antennas with nearby metal structures. The analytical calculation of the pattern of the antennas mounted on large complex structures are difficult, time consuming, and sometimes impossible. So predictions by either numerical or asymptotic methods are preferred.In order to solve the electromagnetic compatibility (EMC) problems of multiple antennas mounted on shipborne platforms, by comparing with variety of electromagnetic algorithms, the multilevel fast mutipole algorithm (MLFMA) with adaptive number of levels is implemented in this paper. Then it gives an analysis of the theory and process of this algorithm, and brings out two kinds of model building methods. Subsequently, a typical warship model is build and showed.Secondly, the analysis pattern and mutual coupling which has been performed in the 3~30 MHz frequency range and antennas are located on the topside of the ship. For the analysis of the coupling between antennas, the definition of arbitrary isolation between antennas is put forward according to the microwave network theory considered. Basing on Multilevel Fast Multipole Algorithm, this paper analyzed, calculated and simulated the radiation field of single whip antenna in short wave on warship, and mutual coupling in different conditions include frequency, length, horizontal and vertical distance, polarization, etc. And then, a destroyer is simulated and analyzed.Finally, the paper discuss the characteristics of near-field Electromagnetic field, and compared with the radiation characteristics and layout of the antennas with the different warship superstructure size, antenna positions, antenna numbers and transmit power, which provided one means to the design of the communication warship. Another, an antenna optimization layout algorithm based on the eigenvalue decomposition of antenna inter-coupling matrix is implemented, which is rational and applicable for optimizing the layout of multiple antennas mounted on shipborne platforms.