Noval Broadband Planar Antennas For Base Stations

As important components of mobile communication systems, base station antennas havedirect and important influences on the performance of the mobile communication networks.With the development of communication technology, different mobile communicationsystems have been designated with different frequency bands, which need broadband,multi-band, dual-polarized and miniaturized base station antennas. The mian focus of thisdissertation is on the design techniques of novel broadband planar base station antennas. Fivebroadband base station antennas with planar configurations are proposed. The maininnovative contributions of the dissertation are summirzed as follows:1. A broadband planar base station antenna is proposed. The antenna consists of a pair ofhalf-wave dipoles, which are connected in parallel through a coplanar stripline andcoupling fed by an L-shaped microstrip line. The influences of coplanar microstrip line,the L-shaped microstrip line and the distance between the antenna and reflector on theimpedance bandwidth are investigated. Experimental results show that the antenna has a15-dB bandwidth of54%(1.65-2.85GHz). The antenna gain is9dBi. The radiationpatterns are stable. An eight-element broadband planar antenna array is developed forbase station application.2. A broadband planar45°dual-polarized base station antenna is developed based on thebroadband planar base station antenna. The antenna consists of two broadband planarbase station antenna elements. The influence of different arrangements for the45°dual-polarized antenna elements on the isolation is investigated. Experimental resultsshow that the antenna has a15-dB bandwidth of48%(1.69-2.78GHz) and a highisolation of30dB. An eight-element broadband planar45°dual-polarized antenna arrayis designed for base station applications.3. A broadband planar vertically/horizontally (V/H) polarized base station antenna isproposed based on the broadband planar base station antenna. The antenna is composedof two perpendicularly placed broadband planar base station antenna elements. Thehorizontal plane is the H-plane for the vertically polarized (VP) element and the E-planefor the horizontally polarized (HP) element. By shaping the reflector for the antenna, ahalf-power beam width of62.53°is achieved for both vertical and horizontalpolarizations. The antenna has a15-dB bandwidth of47%(1.7-2.75GHz), an isolation of30dB. An eight-element broadband planar V/H dual-polarized antenna array is developed for wireless communication applications.4. A broadband planar dual-polarized four-leaf clover antenna is proposed forLTE700/GSM850/GSM900base station application. The antenna is composed of twoperpendicularly crossed bow-tie dipoles. Each bow-tie dipole is excited by a microstripline. This type of feeding structure avoids using any wire bridge, wire bonding, shortingpin, or feeding probe, making the dual-polarized antenna planar and compact. Due to thecoupling between two bow-tie dipoles, the antenna achieves a broadband bandwidth.Experimental results show that the antenna has a15-dB bandwidth of50%(0.63–1.04GHz) with an isolation of35dB. A four-element broadband planar dual-polarizedfour-leaf clover antenna array is developed, which is suitable forLTE700/GSM850/GSM900base station application. Since the antenna has advantages ofsmall size and large bandwidth, a broadband planar dual-polarized antenna and itseight-element array are also developed for2G/3G/LTE (4G) base station applications.5. A dual-broadband planar base station antenna is presented. The antenna consists of a pairof printed dipoles for the lower band and two pairs of printed dipoles for the upper band.The upper-band elements are nested inside the lower-band element. Therefore the antennahas a planar and compact configuration. The antenna achieves a bandwidth of20%(800-980MHz) for the lower band and a bandwidth of60%(1540-2860MHz) for theupper band. A four-element dual-broadband planar antenna array is designed for2G/3G/LTE (4G) application, which leads to a4-element array for the lower band and an8-element array for the upper band. Since the number of elements for the upper-bandarray is twice of that for the lower-band array, the grating lobes can be avoided.This thesis has conducted a comprehensive investigation and research on the operationprinciple and design tecnniques for the broadband planar base station antennas. New methodsfor the design of the broadband antenna are provided.