Studies On Some Key Techniques Of Low Profile Broadband Base Station Antennas

In recent years, with the rapid progress of wireless mobile communication technology, the 3G technology becomes matured and the 4G technology is getting widely used. The capacity and transmission rate of wireless mobile communication system are demanded more and more higher. As a key sub-suystem of wireless mobile communication system, base station antennas are confronted with great challenges. Due to the deficiencies such as high profile, high cross-polarization and narrow bandwidth, conventional base station antennas are not suitable for the new wireless mobile communication systems. Thus, base station antennas with low profile, wideband and low cross-polarization have significant research values.This thesis mainly focuses on the studies of the low profile,wideband bandwidth and low cross-polarization characteristics of the base station antennas. Some methods used to improve the performance of base station antennas are presented. Moreover,relevant antenna models are designed,manufactured and measured. Experimental results are in good agreement with the prospective design specifications.The main contents of this thesis can be summarized as the following four parts:1. Firstly, the development status and background of base station antennas are described in this thesis. Some basic theories and main requirements of base station antennas are also reviewed.2. Some conventional techniques to broaden the bandwidth of base station antennas are presented. The advantage and disadvantage of these techniques are also summarized. A low profile, dual polarized antenna with a bandwidth from 1710 MHz to 2170 MHz is proposed and designed. With the use of differential feed and parasitic strips, this antenna achieves broad bandwidth of 23.7% and a low profile of being 20 mm, including a 3mm radome and a 2mm ground reflector. Experimental results show that the designed antenna can be used to achieve anticipated effects.3. Focused on the requirements for wideband and low cross-polarization, this thesis presents a wideband basestaion antenna with sawtooth fences. The cross-polarization at the edge of ±60° angle spaces is significantly improved. The beamwidth is about 65°±5°over a wide operating bandwidth. The feasibility of the presented model is verified also by experiments.4. A 1×2 stacked patch antenna array fed by L-shaped strips is designed for the requirements of 1710-2170 MHz base station antennas. The designed antenna array shows a bandwidth of 23.7% for S11<-10 dB, with an overall profile thickness of 0.1λ(16mm) at the center operating frequency. By using of same amplitude but anti phase feeding, the isolation is improved remarkably with S21<-32 dB. The antenna is simulated with commercial software HFSS.