Research And Design Of Dual Band 3G And LTE Electrically Tunable Base Station Antennas

Base station antennas work as a transit hub for mobile communications, its performance has a direct impact on the quality of the whole communication systems. Now, the buildings with complex structures in urban become more and more crowded, which need us have to adjust the tilt angles of the station antennas to guarantee the signal’s transmissions through the obstacles. However, the traditional non-electric tunable antennas are hardly to realize it. In this case, the electrically tunable antenna s have significantly advantages. In addition, with the popularity of LTE(Long Term Evolution), in order to reduce the costs of installation and maintenance of base station antennas, the frequency bands of the base station antennas need to be compatible with the previous operating frequencies. Therefore, multi- frequency technology, broadband technology, and the dual-polarized technology of the antennas stimulated more and more researcher’s interest. In this paper, an electrically tunable base station antenna who works at dual-band 1710-2170 MHz & 2500-2690 MHz is proposed. Its feed network including power divider, phase shift, and other passive components is also designed. The main works of our researches are as followings:(1) Based on transmission line theory and power divider theory, two power dividers working at 1710-2170 MHz and 2500-2690 MHz respectively are designed. The voltage standing wave ratio(VSWR) of this two power divider are less than 1.2, and the insertion loss are less than 0.15 d B, which shows that they can be used in the respective band base station antenna.(2) According to the transmission line and phase shifters theories, two phase shifters operating at 1710-2170 MHz and one phase shifter operating at 2500-2690 MHz are designed. The VSWR of this three phase shifters are less than 1.25 in phase-change range, and the amount of phase shift are more than 110°, which proves they have a good performance.(3) Considering the characteristics of the die-type base station antenna elements, and based on dual-polarized antenna design theory, two types of base station antenna elements working at 1710-2170 MHz and 2500-2690 MHz respectively are designed. The measured results show that the electrical and radiation performances of the two antennas are both meet the requirements of the performance criteria for the base station antennas in engineering applications.(4) On the basis of the beamforming principles of base station antennas, combined with the requirements of practical applications, a feed network of the base station antennas is proposed. A non-electric tunable antenna and two electrically tunable antennas are assembled. The electrical and radiation performance of those antennas are measured. All the experiment’s results demonstrate a good performance.