Design Method Of Mode Decomposition Method Based On Virtual Port For Circularly Polarized Micro-stripantenna

Antenna acts a device of transmitting and receiving in the wireless communication anddetecting systems. Among various antennas, circularly polarized (CP) micro-strip antennaholds many advantages comparing to other antennas. It has been widely used in GPS, mobilesatellite communication, RFID, etc. Traditionally, the design of circularly polarizedmicro-strip antenna is mainly concentrated in selecting proper radiation patch structure,finding two orthogonal modes, and choosing an optimal position to excite the orthogonalmodes. CP radiation can be achieved when these two modes have the same magnitude and arein phase quadrature. In literature an analysis of CP micro-strip antenna was carried out eitherby directly manipulating the eigen-modes expression or with a variational approach when thestructure is simple. As to the complicated antenna structure, some numerical optimizationalgorithms can be used to design and analysis. Also, the theory of current Characteristic Mode(CM) can be applied. In literature some works tried to use this approach, but the applicationof electric field CM has not appeared yet. The major contributions of this thesis aresummarized as follows:1. A method of mode decomposition base on virtual port was proposed. The coefficients ofeigen-modes and the AR were derived based on the cavity theory. The radiation featurecan be estimated from port impedance. The optimal feeding position was found by meansof virtual port method. During the derivation, corner truncated patch antenna was used toverify the method.2. A circularly polarized micro-strip antenna with cross slot was designed. Then thefabrication and measure of the antenna were conducted. Its measured impedance, AR,radiation pattern agreed well with the simulation results. The design procedure verifyhigh efficiency of the method in design of CP micro-strip antenna.3. A dual-band circularly polarized CNSS antenna was proposed. Mode analysis and sizeoptimization simulation are conducted, and the impedance and AR bandwidth can coverthe band of CNSS.4. An aperture-feeding E-slot CP micro-strip antenna was designed. Some important sizeparameters affecting the two orthogonal modes were studied. The method of field decomposition was proposed for optimization of AR, which shorten the simulation time.At last, the fabrication of the antenna was conducted. Its impedance, radiation pattern andgain are measured, which agreed well with simulation results.Through the systematic study, practical operability and extensive applications of themode decomposition based on virtual port is verified. The method enriches the antenna theory.Also, it lays the technical foundation for the future design of CP micro-strip antenna.