Research On Fast Algorithms For Wide-band Electromagnetic Characteristics

In recent years, with the rapid development of information technology, the future wars are no longer the traditional mechanical warfare, but an all-round and multi-level electronic warfare. Radar system plays a vital role in strategic weapon platform. In modern radar object identification and stealth technology, how to obtain the comprehensive information in both wide-band frequency and angular domains accurately and quickly has become the key to the success of the future wars. Therefore, the research on analysis of wide-band electromagnetic properties of targets is not only an academic subject, but also more is of great practical engineering significance. Being associated with the National Natural Science Fund and research projects, this dissertation mainly focuses on electromagnetic broadband rapid analysis methods based electric field integral equation(EFIE) of targets and antennas and its application in wire antennas mounted on platforms and low frequency, the author’s major contributions are summarized as follows:1. The surface integral equations of conductor, wire and conductor-dielectric mixed targets are introduced in detail. And then the electromagnetic radiation and scattering of the perfectly electric conducting(PEC) and composite targets are analyzed using the method of moments(Mo M). The Rao-Wilton-Glisson(RWG) and triangular basis functions are used to solve the distributions of current on PEC and wire, respectively. The RCS of conductor-dielectric mixed targets is obtained by EFIF-PMCHWT method.2. The asymptotic waveform evaluation(AWE) and best uniform approximation technology are introduced in this dissertation for wide-band electromagnetic properties analysis, including theoretical formulation and the algorithm implementation steps. The AWE and best uniform approximation technology are based the Taylor series expansion and Chebyshev polynomial respectively. In order to improve the calculation efficiency and reduce the computer memory required, the adaptive integral method(AIM) is adopted. The applications of AIM in electromagnetic computing are introduced in detail.3. The adaptive integral method is utilized to solve electromagnetic properties of surface-wire junction configurations. To obtain the current density accurately, the triangles-to-segments junction model is adopt, which can express the current rapid variation than surface-surface model. Conductor and wire are discretised and the RWG and triangular basis functions are used to solve the distributions of current on conductor and wire, respectively. The junction yield is processed by using the special surface-wire junction basis function. In order to employ the AIM, the whole junction structure is enclosed in a cube grid. Then the three different basis functions are incorporated into the(p+1)2 grid nodes around the original basis functions. The projection process are mutually independent and the obtained auxiliary basis function are also independent each other.4. The asymptotic waveform evaluation(AWE) and best uniform approximation technology are proposed to analyze the wide-band properties of surface-wire junction configurations. Compared with the conventional point by point calculation method using Mo M, these methods greatly improve the computational efficiency for surface-wire configurations. In AWE, it is needed to calculate the high order derivative. The processing of the high order derivative of junction domain self-impedance matrix is more complicated. However, the best uniform approximation does not need to compute the high derivatives of the impedance matrix and the computational complexity is low.5. The AIM is combined with the AWE technique and best uniform approximation technology to accelerate the computation process of wide-band analysis of surface-wire junction mixed configurations. The AIM can reduce the storage requirements of surface wire impedance matrix and its frequency derivatives matrices. Because of the convolution properties of green function matrix, the FFT can be used to accelerate the matrix-vector multiplications during the iterative solution. Compared with the AWE, the combination of AIM and best uniform approximation technology is easy to implement. The theoretical basis of this algorithm is simple and the program code is easy to write.6. An efficient wide-band analysis that based on Loop-tree basis function is proposed. For the traditional Mo M, the low frequency breakdown problem limits its application in EM problem analysis when the low frequency band is considered. In order to solve the low frequency breakdown problem, the method of decomposition of the magnetic vector and electric scalar potential is usually used. This decomposition can be achieved by the Loop-tree basis function. Then the Loop-tree basis function is utilized to analyze the monostatic RCS over a given angle band or over a given frequency band by combing the AWE technique and best uniform approximation technology. Compared with the traditional method, this proposed method can reduce the computation time largely.