Study On Wide-band And Wide-angle Scanning Performance Of Phased Array Antenna Based On Tightly Coupled Structure

With the rapid development of wireless communication technology,multifunctionality and integration are increasingly prominent trends for RF and antenna systems.It is required to provide wide frequency bandwidth and beam scanning range for phased array antennas.While the conventional phased array antennas need to suppress the mutual coupling effect between elements in the design process,the tightly coupled arrays(TCAs)utilize the strong coupling effect between adjacent elements to improve the bandwidth of the array.The TCAs have the advantages of broadband frequency range,wide-angle scanning and low profile,and provide a new design methodology for the realization of phased array antennas with ultra-wide bandwidth and large angular scanning.To this end,this thesis studies tightly coupled phased array antenna featuring low-profile,ultra-wide bandwidth and wide-angle scanning,by incorporating miniaturized feeding balun technology and wide-angle impedance matching technology.The main contents of this thesis are summarized as follows:1.A single-polarized tightly-coupled phased array antenna with square lattice is studied.The impedance matching status of the array under beam scanning circumstances are improved by loading parasitic dipoles above the excited tightly-coupled dipoles.By further loading a metasurface layer in the form of metal square rings above the dipoles,as the wide-angle impedance matching layer of the array,wide frequency band and wide scanning volume are obtained despite ultra-low profile.In order to effectively feed the tightly-coupled dipoles,a miniaturized and integrated Marchand balun is adopted.By etching width-gradient small slots on the ground layer of balun and meandering the signal layer of balun,the impedance bandwidth is further improved while the ultra-low overall profile of the antenna is retained.By employing compensation technology with extension for the edge effect of array,the semiinfinite periodic array and finite array are analyzed and compared.Finally,the designed tightly-coupled array exhibits bandwidth of 7.9:1(1.89 GHz – 14.9 GHz)with ±45°scanning in the elevation direction,under the condition of active VSWR≤3.2.A single-polarized tightly-coupled phased array antenna based on sub-array within a rectangular lattice is designed.In order to reduce the impedance transformation ratio of the balun and reduce the design difficulty of the feeding structure,the configuration of dual element sub-array is adopted,on basis of the relationship between the period of rectangular lattice and scanning impedance.That is,each excitated sub-array contains two identical radiator elements,and the feed structure is composed of two exponentially tapered baluns and a Wilkinson power divider.The common mode resonance is suppressed by short-circuit structure.The impedance matching performance of the array at low frequencies are improved by etching an arc slot at the end of each dipole to introduce capacitive coupling.The 10 × 10 finite array is analyzed,demonstrating an operating bandwidth of 9.3:1(1.9GHz – 17.8 GHz)and a scanning angle of ±45°,under the condition of active VSWR≤3.3.A dual-polarized tightly-coupled phased array antenna is designed.Based on the design of single-polarized tightly-coupled dipole array,the co-aperture dual-polarized radiation is realized by using square lattice and orthogonal alignment of two single-polarized arrays.Finally,a prototype of finite array is manufactured and tested after incorporating T/R modules.The measured results are well consistent with the simulations.