Research And Design Of Microstrip Planar Reflectarray Antennas

Since the microstrip patch was used for reflectarray designing, microstrip planarreflectarray has enjoyed a rapid development due to its various advantages, such as lowvolume and mass, and simple feed structure. In some domains of communication, themicrostrip planar reflectarray can be an alternative to the parabolic reflectors andconventional microstrip patch array antennas, because it can not only avoid the use ofcomplex feed networks to increase the efficiency and gain of the antenna, but also befabricated with very low cost. In this dissertation, we focus on the two attractivedomains of the reflectarray, wideband and dual-band, and make an intensive study onthem.In chapter1, the research background and significance of this dissertation areintroduced firstly. Then, we review the origin, development history and currentadvancement of planar reflectarray. At last, the main works and arrangement of thisdissertation are outlined.In chapter2, the basic principle of reflectarray and two kinds of element simulationmodels, waveguide simulator and master-slave boundary model, are presented firstly.Then, the advantages and disadvantages of some typical elements are introduced. Toreduce the cost of time in simulation, a simplified model based on the waveguidesimulator is proposed to cut the simulation model into half or quarter of the original one.Finally, by comparing the desired and achieved phase delays for each element in areflectarray, the ways to broaden the bandwidth are introduced and the problems need tobe solved in wideband design are analyzed.In chapter3, aiming at the narrow bandwidth in reflectarray with low-profilesubstrate, a novel reflectarray element is proposed firstly, by properly optimizing itsdimensional parameters, good reflection phase characteristics are realized. To enhancethe bandwidth in further, a wideband method in which the phase delays at two closelyseparated frequencies are matched simultaneously by choosing proper elementparameters is proposed. By using the proposed element and wideband method, a6×10-element reflectarray is designed, fabricated and measured, the simulations agree well with the measurements, a-10dB side lobe level (SLL) bandwidth of15.2%and-3dB directivity drop bandwidth of22.3%are obtained at last.In chapter4, a novel reflectarray element is proposed based on low-profilesubstrate, two dimensional parameters are used to tune the phase delays, a phase rangeof more than360oand approximately parallel phase curves in wide band are realized.Then, a20×20-element reflectarray is designed, fabricated and measured, thesimulations agree well with measurements, a-3dB directivity drop bandwidth of22.7%is obtained at last.In chapter5, some existing structures of dual-band reflectarrays are introducedfirstly, to solve the problems in designing a dual-band reflectarray with small centerfrequency ratio and identical linear polarization, a novel dual-band method is proposedand the element presented in chapter3is used to design a10×10-element dual-bandreflectarray, good dual-band performance is obtained. Then, a visible plot is used toillustrate the completeness of the reflection phase distribution in two center frequenciesof the element, to design reflectarray with bigger aperture, a four-resonance reflectarrayelement is proposed. Finally, a20×20-element hybrid reflectarray with two kinds ofelements is designed, fabricated and measured, the simulated and measured resultsdemonstrate that the dual-band performance is realized successfully.In chapter6, the research works of this dissertation are summarized and the futureworks are predicted.