The Research Of Dual-Frequency Dual-Polarization Multi-beam Antenna Array Based On Wideband Butler Matrix

In the field of antenna,multi-beam antenna technology is more and more widely used,especially multi-beam antenna based on Butler matrix has attracted a lot of researchers attention.At the same time,the dual-frequency dual-polarization multi-beam antenna array with multi-beam scanning and dual-frequency dual polarization performance has gradually become one of the hotspots in antenna research.In this paper,the broadband Butler matrix and dual-frequency dual-polarized(DFDP)antenna are studied,and the multi-beam system composed of Butler matrix and dual-frequency dual-polarization antenna array is designed.Finally,the simulation and measurement are compared and analyzed.Due to the Butler matrix acting as a beamforming network(BFN)for multi-beam antenna systems,a new structure is proposed for its basic element: 3d B directional coupler with two-stage coupling structure.Compared with the traditional gap coupling structure,the use of two-stage coupling structure greatly reduces the difficulty of design optimization,and debugging is simple.The coupling error range of the coupler is(3 ±1)d B and the phase change range of 89 ~ 97o o in the ultra wide band range from 3GHz to 12 GHz.Similarly,the 45o phase shifter,which is one of the core elements of the Butler matrix,is a four-port phase shifter consisting of a 90o dual-port differential phase shifter deformed by a 3d B directional coupler and a reference line.The amplitude of the reflection coefficient at the input of the differential coupling branch can be kept below-10 d B,and the phase error is kept(45 ±5)o,within the UWB range from 3GHz to 11 GHz.4×4 Butler matrix is a combination of two-stage coupling structure UWB 3d B directional coupler and ultra-wideband 45o phase shifter as the basic unit.The amplitude of the transmission coefficients of the Butler matrix in the wide output range is kept within the(-8 ±2)d B fluctuation.while each input is entered separately,phase errors are-45 ±5o o?135 ±5o o? 135 5-±o o and 45 ±5o o in the broadband respectively,thus the broadband 4×4 Butler matrix is achieved.The basic form of the antenna structure used in this paper is slotted coupled microstrip antenna.Firstly,a bipolar antenna unit operating in the 5.8GHz frequency band is designed.After designing the bipolarization unit,a 3×3 binary bipolar array antenna working in the 5.8GHz frequency band by using the feed network combined with the series feed and the parallel feed is designed based on the basic unit.Finally,a dual-frequency dual-polarized antenna unit operating in 5.3GHz frequency band and 5.8GHz frequency band is obtained.At last,based on the dual-frequency dual-polarization unit antenna,a 4×4 dual-band dual-polarization array antenna is designed,and four identical inputs are placed in each polarization direction for the four outputs of the Butler matrix to form a multi-beam antenna system.The multi-beam scanning is carried out at the frequency point 5.3GHz in the horizontal polarization direction and 5.8GHz in vertical polarization direction respectively.Compared with the simulation results,the deviation between the measured results and the simulated results is relatively small,which meets the dual-frequency dual-polarization multi-beam scanning function.