Research On Broadband Wide Beam Slot Antennas

With the development of wireless technology,the Internet of Things era arrivals.Not only better performance,but also heterogeneous appearance structure are demanded for the antenna because of the fast evolution of smart home products.The terminal products with full-metal structures show wide applications prospect for excellent mechanical properties,fashionable appearance,and soft handling feeling.In this thesis,the antenna designed for full-metal structure and large size are studied systematically.Based on the traditional cavitybacked slot antenna(CBSA),wide-beam and broadband researches are carried out,and two cylindrical conformal wide-beam slot antennas with thin back cavity are designed.Firstly,the realization method of the antenna for full-metal shell is further studied.Based on the theoretical model of the ideal half-wave slot antenna,this thesis discusses experimentally the performances of slot antenna loaded with different thicknesses of the back cavity.The relationship of the antenna impedance and operating frequency,cavity size is systematically analyzed.What’s more,the influence of cylindrical conformal at different bending angles on beam characteristics of CBSA is concluded in detail.On this basis,a cylindrical conformal thin CBSA is designed to cover 2.4 GHz WLAN band.Inverted T-shaped feeding branch is used to couple and feed the slot,so that the minimum actual gain of the antenna is greater than-5 d Bi within the ±90 degree beam coverage of the horizontal plane pattern.Secondly,a dual-band wide beam CBSA is designed based on the above mentioned work.In order to improve the high-frequency mode beam characteristics of the cylindrical conformal thin CBSA,parasitic elements are introduced to disturb the current distribution around the slot.This ensures the high-frequency beam width of the model and broadens the impedance bandwidth of the low-frequency simultaneously.Meanwhile,a short slot is connected in parallel at a distance of 5 mm from the original slot to increase the working bandwidth at high frequencies.The simulation results present that the designed dual-band wide beam CBSA has two-10 d B relative bandwidth of 9.45% and 14.94%,respectively.And,it shows good wide beam radiation characteristics by achieving the ±90 degree beam coverage(＞-5 dBi)in the WIFI dual-band.Finally,physical processing and experiments of dual-band wide beam CBSA are carried out to verify proposed theoretical basis and performance.The main structure is composed of a conformal rectangular back cavity and a metal cylindrical cavity shell with a height of 40 mm and a radius of 80 mm.The parasitic element,the short parallel slot,and the feeding branch are all welded inside the back cavity.And,to keep the radiation surface clean,the 50Ω coaxial line is drilled through the center of the back cavity,whose inner core is welded on the feeding branch,and the outer skin is welded on the metal ground leading from the cylindrical surface to the back of the feeding branch.The experiment and simulation results are basically consistent,which verifies the reliability of the proposed theoretical basis and design method.