Research On Novel Circularly Polarized Dielectric Resonator Antennas

With the rapid development of modern wireless communication systems,the antennas as their key components are required to have higher performance,such as higher efficiency,higher gain,circular polarization and dual bands.Due to their abilities to resist multipath effects,suppress polarization mismatch and improve communication capacity,the circularly polarized?CP?antennas are widely used in communication,radar,electronic countermeasure and electronic reconnaissance systems.Recently,dielectric resonator antennas?DRAs?have attracted more attention in some specific communication systems because they have no metal losses and surface wave losses,and these advantages result in high power capacity and radiation efficiency.Meanwhile,the substrate integrated waveguide?SIW?technology has been used in microwave active and passive devices due to its low cost,low profile,high quality factor and easy integration,especially in feeding networks of the antennas.Combining the advantages mentioned above,a CP DRA fed by back-cavity substrate integrated waveguide and a dual-band CP DRA are designed.The main contributions of this thesis are summarized as follows.1.A novel high gain CP DRA array fed by a back-cavity SIW operating in millimeter wave?MMW?band is proposed.First,a CP DRA unit fed by a single slot on the surface of SIW is designed.The unit is a rotated-laminated structure,which has the advantages of high circular polarization purity and easy integration with the feeding structure.Then,the cavity mode of TE₄₄₀ is studied and a 4×4-element CP DRA array fed by the slot coupling of back-cavity SIW is proposed on the basis of the proposed unit.The array has a good circularly polarized characteristic in the 27.81-28.17 GHz band.The minimum axis ratio?AR?is less than 0.5 dB,and the maximum gain is 16 dBic.The simulated results are in good agreement with the measured ones.2.A novel dual-band CP DRA operating in MMW band is proposed.The antenna is fed by a microstrip-cross slot,and the radiator is a rectangular DRA with layered truncated corners.Two modes of Quasi-TE₁₁₁ operating at 21.7 GHz and 23.8 GHz are used to realize wideband circular polarization in the lower band.A mode of Quasi-TE₁₁₃ operating at 28.2 GHz is adopted in the upper band,which not only realizes a CP radiating characteristic,but also improves gains of the antenna in this band.Compared with the lower band,the average gain is 3 dB higher.The impedance bandwidths(|S₁₁|<-10 dB)of the proposed antenna in the lower and upper band are 17%?20.5-24.3 GHz?and 15.2%?26.1-30.4 GHz?respectively.The AR bandwidths?AR<3 dB?are 12.8%?21.2-24.1 GHz?and 5%?27.4-28.8 GHz?,respectively.The maximum gain values are 5 dBic and 8 dBic,respectively.The designed antenna has stable gains and good directivities in the two operating bands,and the simulated results are in good agreement with the measured ones.