Filter Antennas For Decoupling Of Multi-Array Basestation Antennas

The development of mobile communication systems is changing with each passing day,and the fifth generation mobile communication system(5G)is gradually towards large-scale commercial use.The arrival of 5G has put forward higher requirements for mobile communication systems,and base station antennas,as the"ear and eyes"of communication systems,naturally need to meet higher challenges.The arrival of 5G does not mean abandoning the previous 2G/3G/4G communication systems.On the contrary,in mobile communication systems,they need to coexist to meet the needs of people's lives,which has caused the number of base station antennas used for communication to multiply.Because the cost of base station construction is huge,and the land and space available for base station construction are limited,the builders have to try to place base station antennas that work in different frequency bands in a limited,narrow space.The number of base station antennas increases,and the construction space does not change.The spacing between antennas is naturally close.The most significant problem brought by the proximity of antenna spacing is mutual coupling.Problems such as antenna mismatch and pattern distortion caused by mutual coupling will eventually affect the normal operation of the antenna,which brings difficulties to the miniaturization of base stations.Therefore,how to realize decoupling has become a hotspot of base station antenna research.On the other hand,in order to achieve miniaturization of communication front-end devices,research on multi-function devices has been extensively studied in the field of communication.The filter antenna is also one of many microwave multifunctional components.The combination of antenna and filtering functions in a single component can not only achieve miniaturization of the system,but also improve antenna selectivity.Most importantly,recent studies have shown that filter antennas can also play a key role in decoupling arrays.In the previous decoupling methods,the isolation between antennas has improved,but most of them have been achieved at the expense of the characteristics of the radiation pattern.In the base station antenna,the radiation pattern characteristic is an important index to measure the quality of the base station antenna,so decoupling needs to improve both the isolation and the radiation pattern.In this case,the filter antenna can play an important role.The research work of this thesis is as follows:1.Two compact dual-polarized broadband base station antenna element are designed,which use the principle of a multi-mode antenna to widen the antenna bandwidth.At the same time,a cut-off design is performed on the edge of the antenna to control its impedance matching characteristics so that it can cover the 2G/3G/4G LTE communication band(1710-2690MHZ).The size of the antenna radiation patch is controlled within 50*50mm~2,which realizes the miniaturization of the base station antenna.2.Using the principle of the resonator,a ring-resonantor and a slot are introduced beside the feeder or on the antenna radiation patch to achieve the purpose of filtering.Based on the broadband base station antennas designed in 1,two single-band second-order filtered base station antennas,a dual-band filtered base station antenna,and a dual-band second-order filtered base station antenna are introduced.The introduction of high-order filtering improves the selectivity of the filtering band provides a basis for subsequent research on array decoupling.3.Based on the principle of space current cancellation,a second-order filtered base station antenna was designed.By introducing parasitic elements next to the radiation patch,resonance occurs at the target frequency and cancels out with the radiated current of the excited antenna,thereby achieving the purpose of filtering.Also,due to its second-order characteristics,the filtering band has good selectivity.4.Based on the multiple filter antennas designed in 2,3,the filter decoupling principle was verified.The receiving and transmitting antenna elements form an array.The receiving and transmitting antennas are mutually filtered,and the working frequency bands are staggered,which does not affect each other's working frequency bands.At a small distance,the antenna elements can achieve high isolation and stability radiation pattern.Compared with a large number of existing decoupling technologies,the filtering decoupling technology has a relatively large breakthrough in the issue of pattern preservation.