| With the development of wireless communication towards high frequency, it increased the requirement of high speed on upload and download for base station antenna. The performance of antenna element would affect the property of base station antenna in communication system. At the same time, small base station has received many attentions because it has the virtue of intensifying network coverage, increasing network capacity and improving user experience. The air base station plays an important role in rescue and emergency communication as well. All of these new situations raise the demand of antenna with novel characteristic. Since dielectric resonator antenna(DRA) has been proposed first time in 1983, positive attributes of these radiators such as their broadband nature, high radiation efficiency, small size, light weight, low loss, easy of excitation and stable patterns make them particularly attractive for a variety of applications. Therefore, it is very prospective for wireless communication system to design a new kind of base station antenna based on dielectric resonator.In Chapter one, it first introduces the research background and significance of base station antenna based on dielectric resonator. Then it presents theoretical foundation and coupling mechanism of DRA and investigates the current state of the art on dual polarized, wideband and circularly polarized DRA around the world. At last, the main work and construction of this thesis have been presented.In Chapter two, a dual-, wide-band dual-polarized dielectric resonator antenna with high isolation and low cross-polarization has been introduced. The proposed antenna has realized dual-polarized by applying slot coupling and balanced strip feeding, which achieved high port isolation of-52 d B and low cross-polarization in operational band. The fundamental mode 111 TE and higher order mode 113 TE have been excited for dual-band application. 112TE(10)?(δ < 1) mode, a new kind of mode never be mentioned, is the first time to be proposed. Each operation mode has been discussed and analyzed. 112TE(10)? mode and strip mode are merged with previous mode for wideband application. It’s suitable for this application of base station antenna in F(1880 – 1920 MHz), A(2010 – 2025 MHz), D(2575 – 2635 MHz) band. The related work in this chapter was published in international conference.In Chapter three, a novel two-element wideband dielectric resonator antenna fed separately by two different slots had been introduced. This antenna consists of two identically cylindrical dielectric resonator elements, one of them is coupling energy of feeding microstrip line through a slot and the other using a stepped impedance microstrip feed line to excite the stepped slot. The shift of resonant mode with the variety of slot length and its matched feeding microstrip stub length has been demonstrated. When change slot length and its matching stub length, fundamental mode of 111yHEM or high order mode of 212yHEM could be excited individually. The wideband characteristic is achieved firstly by combining different resonant mode of two identical elements and secondly by producing the novel model since coupling between two elements. An equivalent rectangular DRA model has been introduced to analysis the coupling between two closed elements. This kind of antenna can be used for 2G/3G/LTE small base station antenna. The related work in this chapter has submitted in IEEE Trans. Antennas Propag..In Chapter four, a wideband circularly polarized dielectric resonator antenna fed by broadband feeding structure has been introduced. The broadband feeding structure was composed of Wilkinson power divider and broadband 90 degree phase shifter. Firstly, broadband feeding structure was used to feed single band DR. Impedance and axial ratio(AR) bandwidth was wide as expected, but the 0 d B gain bandwidth was narrow. It weaken wideband characteristic of impedance bandwidth seriously. Then, broadband feeding structure was used to feed dual band DR. Impedance and AR bandwidth was same as the single band model. Gain bandwidth was enhanced at the same time.In Chapter five, it concluded the summary of the thesis and proposed possible improvement approaches in the future. |
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