Research On Dual-band Dielectric Resonator Antennas

With the development of material science, homogeneous dielectric material with high permittivity and high thermal stability has come forth, which provides the material foundation for the industrial production of dielectric resonator. Many researchers have devoted themselves into study on dielectric resonator antenna (DRA) last three decades and much literature with theoretical and practical value are published, which establishes quite firm theoretical basis for later research. Dielectric resonator antenna with so many attractive advantages as low loss, high Q-factor, easy to feed, and etc. has been of good graces from a large number of R&D staffs in radio equipment industry and used widely in a number of radio communication fields. It can be predicted that DRA will play a quite significant role in future with broad prospects for development.DRA consists of dielectric resonator and feeding structure:the former determines the performance of antenna and the frequency bandwidth as well as radiation directivity of antenna are mainly determined by the resonant frequency and field distribution of dielectric resonator; and the latter plays an important part in deciding which one or several modes resonated. DRA could be excited by coaxial probe, microstrip, slot-coupled, coplanar waveguide (CPW) and dielectric mirror line coupling and so on. The eigenvalues of rectangular and cylindrical dielectric resonators will be studied, as well as the distribution of resonant modes, as the theoretical basis for following study.A wideband DRA and a dual-band DRA are designed, of which feed methods are similar, for the wideband DRA can be seen as multiple antennas with narrow band, just connecting each other as a whole.The coaxial probe, for its advantage of availability of a wide bandwidth, is adopted to excite the modified dielectric cylinder to achieve a wideband DRA and the hemispherical dielectric with air cavity to achieve a dual-band DRA as well. The operation bandwidth of the wideband DRA covers from8.6to25.9GHz, based on which the impedance bandwidth, namely100%, can be calculated while the dual-band DRA covers the frequency band3.4-4GHz and5.3-5.9GHz, which contains WiMAX band and ISM (5.8GHz)&U-NII2band, respectively.In this thesis, the performance of DRA changes with the modification of geometry of dielectric resonator by comparing for further study, mainly in new band excited, so that DRA can radiate in broadband or dual-band even multi-band. The simulation results show that split cylindrical dielectric resonator can be used to enhance the bandwidth of antenna. However, the destruction of good symmetry of the dielectric cylinder would result in the deterioration of far field radiation pattern of DRA, possibly in low identity of radiation pattern in the whole band, but that may provide an opportunity for design of multi-beam antenna.