Design and realization of passive phase shifter for non mechanical 1.8 GHz BTS antenna tilting

摘要

In a cellular telecommunication, BTS becomes the important component. BTS antenna must have a good tilting control capability to optimize their coverage. Tilting is the ability of an antenna to focus the main lobe to the direction that is wanted. Many of techniques had been developed by many researchers to have tilting control capability. In this paper, we propose a low cost technique that can make tilting becomes easy and cheap using passive phase shifter. By applying higher permittivity to cover each branch of transmission line of the array antenna from Alumina, a non mechanical tilting control can be provided. The 1.8 GHz BTS antenna with 4 elements array is designed. This antenna is designed with meander microstrip line and 0.4 λ spacing. The dielectric material is alumina with permittivity 9.4. In this paper, the characteristic of several dielectric materials with different permittivity are also investigated to look the effects of changing some parameters. But at the implementation stage, we choosed only alumina as passive phase shifter component. The antenna has been implemented on an FR-4 Epoxy PCB. From the simulation and measurement results we can concluded that small Alumina sheet can be used as low cost passive phase shifter to give 0°–3.5° tilting control. Moreover, these Alumina sheets which cover the transmission lines of the array antenna will also enhance the return loss of the array antenna.