On The Mathematical Modeling And Numerical Analysis Of Microstrip Antennas

Great progress in modern mobile communication technology and electronic warfare makes it an urgent and important issue to design broadband microstrip antennas and microstrip antennas with low RCS for military and civil communication systems. Being associated with three research projects, this dissertation is mainly concerned with the fast computation of multilayered microstrip antennas, computation of RCS of large scale structures, computation of large microstrip antenna arrays, designs of broadband microstrip antennas and microstrip antennas with low RCS. The author's major contributions are outlined as follows:1. The basic principle and operating process of the computation of the spatial Green's functions of planar multilayered media with discrete complex image method (DCIM) are investigated. The near field and far field Green's functions are computed with surface waves being properly dealt. Analysis and comparison is carried out on the expansion functions and integral paths through which a proper expansion function and integral path is proposed to compute the spatial Green's functions of planar multilayered media accurately and efficiently.2. The spatial-domain moment method based on mixed potential integral equation (MPIE) is investigated, which can be used to compute the electrical properties of planar multilayered microstrip structures. Based on the spatial Green's functions calculated by DCIM, the moment method with RWG basis functions is employed to solve the MPIE in order to analyze the electrical properties of arbitrary shape multilayered microstrip antennas. First, the scattering of microstrip patch is analyzed, and then the properties of microstrip-line fed microstrip antennas are investigated using the delta gap voltage source model to simulate the feed structure. The magnetic current frill excitation model is introduced to simulate the feed structure, thereafter, the properties of coaxially fed microstrip antenna are calculated with additional mode basis functions being introduced to simulate the current distribution at the wire/patch junction.3. Adaptive integral method (AIM) is employed to fast compute the radiation and scattering properties of electrical large-scale structures. The scattering of large-scale perfectly conducting objects is calculated with the storage requirement and computation time being greatly reduced. Combined AIM with the spatial-domain MOM based on MPIE, the scattering and radiation properties of large-scale microstrip patch arrays arefast analyzed with less storage requirement.4. Design and prototype manufacture of broadband microstrip antennas are carried out. Using multilayer structure and introducing a circular metal patch on the top of the probe to counteract the inductance of the fed-probe, the bandwidth of the antenna is greatly increased. Using the method, two broadband microstrip antennas which work on 740~960MHz and 1.813-2.319GHz, respectively, are designed and manufactured.5. RCS reduction of microstrip antennas is investigated. The mechanism of RCS reduction of microstrip antennas by cutting slots on the patch is investigated. The effects of different slots on the radiation and scattering of microstrip antennas are analyzed with the spatial-domain MOM, and a slotted microstrip antenna with good radiation properties and low RCS is designed. Then, the applications of meshed microstrip antennas to RCS reduction are analyzed. The effects of mesh-line width, mesh-line spacing and mesh style on the microstrip antenna is analyzed, and a meshed microstrip antenna with good radiation and scattering properties is designed.