The Design And Realization Of Broadband And High Gain Antennas

There is considerable interest in the use of microstrip antennas because of its many attractive features, such as low profile, light weight, easy manufacture. However, classical microstrip antenna has major drawbacks such as narrow bandwidth and low efficiency. On the basis of analysis of broadband antennas and high-gain antennas, this thesis focuses on the analysis of a stacked curved slotted microstrip antenna, a L-probe fed slotted microstrip antenna, broadband EBG structures and dielectric resonator antennas. Three kinds of broadband and high gain antennas are proposed, two of which are fabricated and measured. The test results show that these antennas have good characteristics of bandwidth, gain, and radiation pattern.This thesis is divided into five parts. First of all, the paper introduces the significance and status of broadband and high gain antennas, and discusses the used numerical calculus method and 3D simulation software.Secondly, a new kind of microstrip antenna with curved slots which is used to broaden the bandwidth is proposed. Then, this antenna is combined with a two-layer structure, becoming a broadband high-gain microstrip antenna. By using the 3D numerical simulation software, an ordinary rectangular microstrip patch antenna is simulated, optimized and compared with the proposed one. This antenna is fabricated and measured. The measured results indicate that the stacked antenna has a wider bandwidth and higher gain than an ordinary one.Thirdly, a kind of L-probe fed slotted microstrip patch antenna is analyzed. The design adopts contemporary techniques: L-probe feeding, patch structure with air-filled dielectric, and slotted patch. The composite effect of integrating these techniques and by using the slotted patch, offer a low profile, broadband, high gain, and compact antenna element. Simulated results indicate that a 27.3% fractional impedance bandwidth is achieved with respect to the centre frequency of 2.6 GHz and the maximum achievable gain is 8.4 dB. Next, The equivalent circuit model for electromagnetic band-gap structure is analyzed, and also the methods of broadening the bandwidth of band-gap are studied. A broadband EBG structure is proposed and used to increase the gain of a dielectric resonator antenna. The simulation results show that this kind of broadband EBG structure increases the gain of the dielectric resonator antenna up to 8dB in a frequency range of 180MHz,which is better than the circular EBG structure proposed in [53].Finally, the thesis summarizes the entire work and the future prospect of the relevant research work.