An effective way regarding to coupling reduction and pattern correction in base station design

An effective method regarding to coupling reduction and pattern correction in base station antenna design is developed. Initially, a hybrid antenna with one lower band element, two middle band elements, two higher band elements, and a reflector is designed. It is found that a "C-shaped" current loop is formed by the horizontal radiating arm of the middle band element, its vertical balun ground, and the horizontal reflector. Strong coupling between the lower and middle band elements occurs, making the lower band beamwidth nonconvergent. Hence, a middle band element with comparatively enclosed feeding structure is chosen to interrupt the resonant loop, thus weakening the coupling among those elements. Then, a pi-shaped metal plate and rectangle baffles are added to finely reshape the radiation pattern of these elements. As a result, the coupling between these elements are weakened and the HPBWs of the proposed antenna can keep an extremely stable value of 65 degrees +/- 5 degrees. The discovery and analysis of coupling mechanism has great value for improving the radiation performance of the antenna array.