| With the rapid development of wireless technology,the radio spectrum has expanded to the millimeter-wave band gradually.The radiator of a dielectric resonator antenna(DRA)is fabricated by dielectric materials,which avoids large ohmic losses of the metal antennas in the millimeter wave band,making the DRA be suitable for the future radio system applications.At the same time,many practical radio systems have put forward higher and higher wide-beam performance requirements for the antennas.The wide-beam DRAs have great potential in future radio systems,and high potential application value in many fields such as autonomous driving and satellite positioning.Therefore,how to widen beamwidths of the DRA is a future-oriented reseach topic with high academic value.Based on basic theory of the rectangular DRAs and closed-form expressions of their internal and external fields,several methods for broadening their half-power beamwidths and axial ratio beamwidths are studied intensively in this thesis.The main contributions of the thesis are summarized as follows.1.Based on the internal field expressions of the rectangular DRAs,a method for broadening beamwidths of the DRAs is proposed.In order to verify effectiveness of the method and explain its principle,a linearly polarized rectangular DRA resonated at TE113y mode is designed.By loading two pairs of higher-permittivity dielectric slabs,the E-plane beamwidths of the DRA are broadened.Moreover,two sides of the metal ground plane are folded down,and the H-plane beamwidths are broadened too.By changing some important parameters,the E-plane and H-plane beamwidths of the DRA can be adjusted effectively.Measured results indicate that its maximum E-plane and H-plane half power beamwidths are 210° and 137°,respectively,while its E-plane and H-plane half power beamwidths are greater than 120°throughout the usable bandwidth from 3.02 to 3.26 GHz(relative bandwidth 7.6%),and its gains are over 2.2 dBi.For further verifying the guiding significance of the proposed design method,a derivative design scheme is also proposed.By opening a cavity on the top of the rectangular DRA,the E-plane beamwidths can also be widened.2.Based on the feeding theory of the DRA derived from Lorentz's reciprocity theorem,a wide-beam circularly polarized rectangular DRA with a composite feeding structure is proposed.The composite feeding structure consists of a slender rectangular slot fed by a microstrip line and a pair of printed bent metal strips.The rectangular slot excites the TE1?1y mode of the rectangular dielectric resonator,while the printed bent metal strips excite the TE?11x mode.By adjusting dimensions of the printed metal strips,a 90°phase difference can be generated between these two orthogonal modes,and then circularly polarized radiation with wide 3-dB axial ratio beamwidths can be realized.In addition,by adjusting size of the DRA to change the aperture size,and reducing area of the metal floor,the half power beamwidths can be widened.Measured results indicate that the maximum 3-dB axial ratio beamwidths in the ??0° and ?=90° planes are 224° and 165°,respectively.Its 3-dB axial ratio beamwidths are greater than 122° in the ??0° and ??90° planes and its half power beamwidths range from 101° to 127° throughout the usable bandwidth from 4.3 GHz to 4.8 GHz(relative bandwidth 11%).Its gains in the ?=0° direction are over 4.7 dBic.In addition,the impedance bandwidth of the DRA is from 3.58 GHz to 5.55 GHz(relative bandwidth 43%),and its 3-dB axial ratio bandwidth is from 4.3 GHz to 4.9 GHz(relative bandwidth 13%)... |
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