Researches On Pattern Reconifgurable Antenna Element And Its Application In Phased Array

Antenna is an indispensable part of wireless information systems. With the rapiddevelopment of current wireless information technology, the performance of antennaelement and array is required higher and higher. For example, antenna element isexpected to work at wideband spectrum with a wide beam and a high gain whileantenna array is required to have high gain and low sidelobe level, and so on. Numerousstudies show that it is a very challenging task to design the antenna elements and arrayson the basis of traditional technology to simultaneously satisfy the several requirementsmentioned above. Therefore people make unremitting efforts to explore new antennaconcepts and technologies to break through the related problems. Recently,reconfigurable antenna concept has been proposed to save the problems. Areconfigurable antenna reconfigures its performance by adjusting the variablecomponents integrated in the antenna aperture, such as PIN switch, MEMS switch, andvaractor diode. Due to the design freedom of reconfigurable antenna, the solution spacesare extended and the potential is exploited for the traditional antenna element and array.Also, a series of new issues come out for the antenna array design. Researches on theanalysis of pattern reconfigurable antenna (PRA) elements and their applications inplanar and conformal arrays have been done in depth and a series of innovativeachievements have been made in this dissertation. Major studies of the dissertation areas follows:In Chapter1, the research background of this dissertation is presented. Firstly, theresearch background and significance of PRA element and array are described. Thentheir development histories and recent advancements are reviewed. Finally, the mainworks and framework of this dissertation are outlined.In Chapter2, three types of PRA are researched and designed. The first type ofantenna is a microstrip Yagi PRA loaded with PIN switches, which resolves theelectromagnetic compatibility between the DC bias net and antenna radiator. The secondtype of antenna is a modified microstrip Yagi PRA with low cross-polarization level, which provides a basis for conformal array to suppress the cross-polarization. The thirdtype of antenna is a Hilbert PRA. The antenna can reconfigure its patterns in eightdirections with wide bandwidth and the space above the antenna plane can be nearlycovered by switching its beams.In Chapter3, the relationship among the radiation pattern, the surface current phaseand the loaded reactance value of the two loaded-dipole array is analyzed in detail. Themechanism of pattern being reconfigured has been researched. On the basis of themechanism, an efficient method of PRA design has been proposed. Starting from thespecific study of the loaded two-dipole array, a model of array analysis is extracted andstudied and we point out that it is an efficient method to design PRA by loading variablereactance component on the antennas with conical beam. According to the method,several PRAs are designed to verify the practical significance of this method.In Chapter4, a new scheme is proposed to design a wide-angle scanning rangearray on the basis of PRA element after the relation between the beam ofplanar/conformal array and PRA element has been researched. The beam scanningperformance of array is improved. Firstly, a few easily confused concepts in arraypattern synthesis are deduced and distinguished. Secondly, the planar/conformal arraysare set up and their patterns are synthesized with the active element pattern method. Inthese arrays the different arrangements and operating states of the antenna elements areanalyzed. The theory and experiment results showed that the new PRA array can scan inwide-angle range. Finally, a method has been proposed to design the PRA array withlarge-scale PRA elements and wide-angle scanning range by analyzing thecharacteristics of the array in which many parasitic dipoles are loaded with variablereactance component.In Chapter5, a hybrid IWO/PSO algorithm is proposed and it is a fast and efficientmethod to synthesize the patterns of PRA array. A microstrip conformal array wasdesigned to validate the advantages of the algorithm over the IWO algorithm and thePSO algorithm. Then some pattern syntheses of the PRA arrays have been preformed byapplying the hybrid IWO/PSO algorithm, which demonstrated that the proposedalgorithm has efficient optimizing capability and has a great potential to solveelectromagnetic problems.In Chapter6, the research work of this dissertation is summarized and the future works are predicted.