Miniaturized Phase Shifter For Electrically Tilted Antennas Based On Slow Wave Transmission Line

The network coverage of mobile communication largely depends on the performance of the base station antenna,which directly affects our communication experience.Nowadays,mobile communication systems put forward more and higher index requirements on the performance of base station antennas.For example,in densely-populated cities,in order to optimize network coverage,this requires that the antenna can change the vertical beam tilt or horizontal beam angle.The device for adjusting the phase difference of the feed in the antenna is the phase shifter,and it's performance directly affects the performance of the electrically tilted antennas.Therefore,it is of great significance to research the phase shifter used in the base station antenna.This article mainly designed two miniaturized phase shifters:An one input seven outputs microstrip fan-shaped phase shifter and an one input five outputs sliding air stripline phase shifter.First of all,I summary the development history of various phase shifters,analyze and compare the advantages and disadvantages of the existing phase shifter.I select an appropriate program as the design of this paper,and explore the basic principles and key technologies of the phase shifter.By calculating the curved line length of microstrip fan-shaped phase shifter and the equivalent stripline length of sliding air stripline phase shifter,I overview the design of phase shift module and power divider module and impedance matching.Most importantly,both phase shifters use slow wave structure,and the curved line of microstrip fan-shaped phase shifter in feeder circuit adopts a waveform structure,so the phase shift is larger than before under the same size,and the waveform structure is easier to match,which makes the phase shifter more convenient for phase-shifting and also facilitates the adjustment of the downtilt angle of the antenna beam.The section of phase shift in sliding air stripline phase shifter includes multiple folded sub-structures connected in sequence to form a slow-wave structure,which substantially increases the length of the phase shift section used for feed,achieves a larger amount of phase shift under the same physical length and reduces the travel of phase-shifting and the overall length of the phase shifter.Therefore,using slow wave structure can reduce the size,weight and cost of the phase shifter,which is beneficial to the miniaturization of the phase shifter.Meanwhile,The design of this paper is microstrip fan-shaped phase shifter,which is an one input seven outputs phase shifter.Since the amplitude distribution balance and line width of the microstrip fan-shaped phase shifter are considered,this type of phase shifter is not suitable to design a phase shifter with number of nine or more ports,and most of the microstrip fan-shaped phase shifters currently on the market are one input five outputs phase shifters,so this kind of phase shifter has strong engineering practicality in terms of miniaturization and number of ports,which can be high-performance applied in electrically tilted antennas.In this paper,an one input seven outputs microstrip fan-shaped phase shifter,which operated in 3300MHz?3800MHz and an one input five outputs sliding air stripline phase shifter,which operated in 690MHz?960MHz are designed.The electrical indicators of the measured data of both indicate that VSWR is less than 1.2,amplitude response fluctuation is within±1dB and the phase dispersion of zero return is less than 10°.The insertion loss of the former is higher than that of the latter.Both phase shifters meet the index of the phase shifter,and it can be actually applied in mobile communication network.