Recent years have witnessed the increasing exhausted microwave band due to the development of the high-speed wireless communication. Thus, investigations on the systems in millimeter wave and submillimeter wave bands are of great significance. Antennas, the important components in the communication systems, have attracted growing number of attentions. In this dissertation, transmission orbital angular momentum antennas, reflection orbital angular momentum antennas, millimeter wave planar circularly polarized antenna arrays and terahertz smooth-walled horn antennas with a high Gaussian coupling efficiency are studied. The dissertation is organized as follows:
Chapter One focus on the studies of transmission planar orbital angular momentum (OAM) antennas. A design method of the planar spiral phase plate (SPP) based on the theory of planar transmission antenna array has been proposed. The proposed planar SPP utilizes a perforated substrate to control the outputting phase for generating beams carrying OAM with arbitrary modes. The transmission phase characteristics of the cell are analyzed with the aid of a full-electromagnetic-wave simulation software. Then, a one-SPP-one-mode and a one-SPP-dual-mode antenna working at 94GHz have been designed with the proposed method. Simulated and measured results including the phase pattern, the magnitude pattern as well as the OAM spectrum are obtained. The results experimentally verify the studies of this chapter. Part of the work is published in Scientific Reports.
Chapter Two focus on the studies of offset-fed reflection planar orbital angular momentum antennas. The design method of reflection planar orbital angular momentum antennas comes from the theory of planar reflection antenna array. A commercial full-wave simulator is adopted to analyze the transmission phase characteristics of the cell, through using the floquent theory. In addition, the cell analysis and the whole antenna system analysis have been carried out to obtain the proper offset distance respectively. An offset-fed reflection planar orbital angular momentum antenna working at 94GHz has been proposed as well. The magnitude pattern, the phase pattern and the OAM spectrum experimentally verity the studies of chapter. Part of the work is published in IET Microwaves, Antennas & Propagation.
Chapter Three focus on the studies of millimeter wave planar circularly polarized antenna arrays. First, a meander-line fed circularly polarized antenna array is proposed, employing the Substrate Integrated Coaxial Line (SICL) and a cavity-backed patch antenna. Moreover, a novel waveguide-to-SICL transition is proposed and analyzed, which provides two sets of differential signal. Based on the novel waveguide-to-SICL transition, a compact planar circularly polarized antenna array working at 75GHz is proposed. The area of the compact array is only half of the conventional one. The achieved bandwidth of the proposed antenna array with measured S11<-10dB is 19.9% (68.1~83.2 GHz). The measured AR below 3dB bandwidth is about 9.3% (71~78 GHz) and the measured peak gain is 12.3 dBi. Part of the work has been accepted by IET Microwaves, Antennas & Propagation.
Chapter Four focus on the studies of a fast and accurate design method for the smooth-walled horn antenna with a high Gaussian coupling efficiency. First, the mode coupling technique has been introduced to analyze the prototype, i.e. the two-flare horn antenna which then has been optimized with a spline profile. In this design method, accurate commercial full-wave simulation software CST MWS, rather than a mode analysis method, is adopted to further improve the Gaussian coupling efficiency performance. As a demonstration, a smooth-walled horn antenna working at 220 GHz has been simulated, fabricated and measured. Both simulated and measured results show that the designed horn exhibit high symmetric, low sidelobe patterns in E-plane, H-plane and 45 degree planes, which verify the proposed design method. Part of the work has been submitted to IEEE Transactions on Antennas and Propagation.