Design And Numerical Analysis Of Miniaturized Microstrip Antennas

With the fast development and the wide applications of the mobile communication technology, the modern communication antennas are required to be compact and achieve multifunctional operations, such as multi-frequencies, multi-polarizations and multi-applications. Accordingly, the design of the compact and multifunctional microstrip antenna is becoming one of the most advanced subjects in the international antenna research field. In this dissertation, the design and numerical analysis of the compact dual-frequency microstrip antenna and compact circularly polarization are detailedly studied in both theory and experientments. The dissertation is classified into four parts stated as follows.Firstly, The calculation formulas of resonant frequency for two kind of dual-frequency microstrip antennas are derived, which is used to determine the design parameters of the dual-frequency microstrip antennas; Using the pulse basic function and mix basic function, the full wave analysis is established by the MoM (method of moment), which can be used to analyze the irregular microstrip antennas; Moreover, a design of dual-frequency for bow-tie microstrip antenna is proposed, the calculation results agree well with the experimental ones.Secondly, The Genetic algorithm is applied successfully to optimize the design of dual-frequency bow-tie microstrip antenna, By optimizing the calculation formula of resonant frequency for bow-tie microstrip antenna , the right coefficient can be found; By optimizing the feed position , the impedance match can be achieved on dual frequency; By optimizing the parameters of the patch and the feed position, the bow-tie microstrip can operate well on dual frequencies.Thirdly, The asymptotic extraction techniques is involved in the MOM for calculating a Sommerfeld type integral problem. Comparing with the general MoM, it is showing that a higher calculation precision and a larger reduction in computation time can be achieved; with a newly introduced organic magnetic materials, a compact and wideband microstrip is designed, Comparing with rectangular microstrip antennas on a normal dielectric substrate, the overall size of the antenna is reduced by 60% and the bandwidth is expanded to 7%, which is about 3times of the normal design.Finally, an study on the compact microstrip antennas with high r substrate and largeground plane is presented. It is shown that, for a large ground plane, the resonant frequency is increased and the antenna circular polarization axial ratio is deteriorated. By loading the active LNA on the antenna, the antenna performance is improved, The proposed antenna shows such advantages as broad impedance bandwidth, low input VSWR and high gain. A novel miniaturized circularly polarization microstrip using slots is given and experimentally validated. The influence of the slots on the resonant frequency and feed position is studied by using HFSS.