Design And Simulation Of A Tightly Coupled Archimedean Spiral Linear Array Antenna

The ultra-wideband phased array design based on the tightly coupled structure is a new idea completely different from the traditional array design.The coupling between the array elements is used to improve the performance of the array.The bandwidth of the array is no longer limited by the bandwidth of the unit.The performance is greatly improved,the unit becomes miniaturized,the lateral area is greatly reduced,and the wide-angle scanning capability is improved.In this thesis,based on the tightly coupled antenna array design theory,taking the one-dimensional close-coupled array with linear polarization as the starting point,a one-dimensional close-coupled antenna array with circular polarization characteristics is designed.Firstly,a one-dimensional tightly coupled array with linear polarization characteristics was analyzed.A single patch dipole exhibits wideband impedance characteristics near 7 GHz,but the bandwidth is narrow;for its non-tightly coupled 16-element linear array simulation,the impedance characteristics of the array element and individual antenna elements are basically the same,and the impedance bandwidth of the array is not widened.A 16-element array with overlapping coupling structures at the end of the cell is simulated.The array unit exhibits an ultra-wideband impedance characteristic at 3~6 GHz,and has a 45° wide-angle scanning capability.On the basis of a tightly coupled array with linear polarization,an ultra-wideband phased array with circular polarization characteristics is studied.Starting from the small Archimedean spiral antenna proposed by H.Nakano in 1986,the characterization of the stripe equivalent,the circular polarization and scan characteristics of the regular array of 5-element arrays are studied.The conventional 5-element array with balun has an impedance bandwidth of 5~6.5GHz,and the non-compacted array spacing of several array elements does not show stable circular polarization characteristics under scanning conditions.Finally,starting from the idea of tight coupling,a tightly coupled Archimedean spiral stripe array with half-band coupling structure at the end of the element is designed.Taking the tightly coupled 5-element array as the basic research object,several key parameters of its coupling structure are simulated and analyzed.The frequency band of the tightly coupled 5-element array with balun under various scanning conditions is basically 5~6.5GHz.The circular polarization bandwidth in the scanning direction is basically the same as the impedance bandwidth,and it still has 1GHz when scanning up to 45°.The properties of tightly coupled 8-unit arrays is studied in parallel,and the tightly coupled 8-unit arrays without balun is basically consistent with the characteristics of 5-element arrays;the frequency band of the tightly-coupled 8-unit array with various scans is 5~6.5GHz.It is consistent with the tightly coupled 5-unit array,but the circularly polarized bandwidth in the scanning case is reduced relative to the tightly coupled 5-unit array.