Study On And Design Of Broadband And Dual-band Dielectric Resonator Antenna

In order to improve the speed and quality of the signal transmitted in the wireless communication systems, the communication standards have been constantly updated. Consequently the antennas, which act as the main elements in the systems, are required to be more compatible. Dual-band and broadband antennas can cover several different frequency bands and can be compatible for more communication standards. Therefore, the study on the basic theory and design method of dual-band and broadband antennas will be very significant.The dielectric resonator antenna(DRA) has received extensive attention in recent years due to its inherent merits such as small size, low loss and high radiation efficiency. As we all know, with the operation frequency increases, the conventional planar antennas suffer from nonlinear ohmic losses, which has a sever effect on the performance of the antenna. However, these losses on DRA almost not exist owning to the absence of the surface waves. Thus the radiation efficiency also can be improved. Hence, DRA can have a good potential in both the wireless communication systems and millimeter radar fields.A dual-broadband DRA and two broadband rectangular DRAs have been designed in this thesis. The main work can be summarized as follows:1. A novel dual-broadband dielectric resonator antenna(DRA) is presented. Based on the modified Sierpinski gasket constructed though two iterations, the proposed antenna display both dual band and wideband features. The total size of the antenna with the ground plane is 0.32λ ×0.27λ ×0.17λ(the center frequency is 2.4GHz) or 0.47λ ×0.43λ ×0.24λ(the center frequency is 3.5GHz), where λ is the free space wavelength at the center frequency. Antenna prototype has been fabricated and tested. The measured impedance bandwidths for S11 <-10 d B are 14.46%(2.25-2.60GHz) and 27.78%(3.10-4.10GHz) respectively, which can cover the wireless local area network(WLAN, 2.4–2.484GHz) and the worldwide interoperability for microwave access(Wi MAX, 3.4–3.69GHz) bands. Meanwhile the maximum gains of the two operation bands are 5.58 d B å'Œ 5.51 d B respectively.2. A broadband rectangular dielectric resonator antenna(RDRA) is presented. A U-shaped slot is used as a feeding structure for a rectangular dielectric resonator. Meanwhile the U-shaped slot acts as an effective radiator. A parasitic H-shaped slot is adapted to improve the impedance match. Simultaneously an air gap is added to further broaden the relative impedance bandwidth. A prototype is fabricated and tested. A relatively broad impedance bandwidth of 73.72% with a maximum gain of 7d B has been obtained. The total size of the proposed antenna with the ground plane is only 0.71λ ×0.71λ ×0.17λ( λ is the free space wavelength at the central resonance frequency).3. A low profile and broadband dielectric resonator antenna of very high permittivity is proposed. The antenna is designed based on a multilayered structure. Two separate dielectric resonators of very high permittivity are placed symmetrically on the top of the antenna structure and a low-permittivity dielectric substrate is put in between the resonators and the grounded dielectric slab to simultaneously realize low profile and relatively large impedance bandwidth. A relative large bandwidth of up to 10.49% has been obtained. Meanwhile gains higher than 6d B and cross polarizations lower than-35 d B over the whole operating band have been observed. The total height of the antenna is 1.57 mm or 0.039 λ( λ is the wavelength at the center frequency).