Research On Antenna Techniques Based On Periodic Structures

Passive electromagnetic periodic structures (PEPSs) has been applied in microwaveantennas, always behaving as a method of realizing artificial electromagnetic materials.Taking CRLH TLs for example, they always are realized by1D periodic structures, whichusually be used in miniaturized microwave filters. Also taking AMCs and FSSs for example,they are realized by2D periodic structures, which have great prospects in low profile and highgain antennas. Thus, further research on the applications of periodic structures in antennas hasgreat significance. By using the method of combining theoretical analysis and experiments,several periodic structures are designed for the miniaturization, notch bands, low profile, andhigh gain of antennas in this dissertation. The main works and contributions in thisdissertation are outlined as follows:1. The technique of extracting dispersion characteristics for1D periodic structure isstudied. A Unit-Cell-Method with high efficiency is advanced applicable to the periodicstructure with weak coupling among cells. When there are strong coupling among unit cells,the Macro-Cell-Method and Uniform-Equivalence-Method are separately put forward interms of the unit cell’s symmetrical properties.2. A low-profile and high gain antenna based on zero-order resonator is designed.Firstly, the characteristic of zeroth-order resonance and the realization of lumped LC networksfor CRLH TL are analyzed. Secondly, the impedance step-up of a single dipole is introduced,and a novel low-profile folded-monopole antenna based on zeroth-order resonance ispresented, which uses two-MTM-unit-cell loaded structure, realizing cophase feedsimultaneously stepping impedance up by ratio of four, resulting in a compact way of feed.Finally, a1D slot-loaded epsilon-negative (ENG) based zeroth-order resonant antenna withimproved radiation efficiency is proposed. Coupling feed and stepped impedance feed arerespectively used for two-MTM-unit–cell and four-MTM-unit–cell antennas, simplifyingmatching method of the antenna, meanwhile realizing a low quality factor with improvedradiation efficiency.3. Various band-notched wideband dipoles are proposed. A method of introducing aninverted L-type or C-type to achieve single band notch characteristic is put forward, orintroducing the two type slots in different place of the antenna as to realize dual band notches.Contemporarily, the working principle is analyzed and corresponding equivalent circuits arepresented. Finally, a novel band-notched monopole antenna based on the periodic structure ofmushroom EBG is designed, with good band-notched characteristic at3.5GHz. 4. A series-fed circularly-polarized array antenna based on CRLH TL is designed.Firstly the theory of CRLH TL is analyzed, also for the realization of the lumped LC networks.Next a series six-way power divider based Zero-Order Resonant is designed, which achievesminiaturization. Then the characteristics of rectangular spiral are investigated, and arectangular spiral antenna with a titled beam is carried out. Finally, a series-fedcircularly-polarized antenna array is designed by combining the series-fed power divider.5. A low-profile and high-gain antenna based on the Fabry-Perot theory is investigated.At first, the properties of reflection and surface band-gap of AMC are studied through doingthe research about its surface impedance in TE and TM mode separately. Secondly, theparametric analysis about the structure of AMC is carried out, obtaining the results that theresonant frequency increases with the main parameters becoming smaller, and meanwhile, thein-phase bandwidth becomes wider with the decrease of these main parameters generally. Theminiaturization, wider bandwidth and multi-frequency of AMC are also under researches.Finally, a low-profile and high-gain antenna based on the Fabry-Perot theory is designed withthe combination of AMCs.