Ultra-wideband Non-uniform Tightly Coupled Array Optimization And Unequal Power Divider Desig

A tightly coupled array is a tightly arranged antenna array that uses the coupling between elements to expand the working bandwidth,thereby achieving ultra-wideband characteristics.And compared to traditional antenna arrays,tightly coupled array can meet the wide-angle scanning requirement,which makes them widely used in radar systems and wireless communication systems.The ultra-wideband tightly coupled antenna is restricted by the sidelobe suppression conditions,and the aperture of the array element is smaller than the half-wavelength of the low frequency,so the gain in the low frequency is significantly lower,which requires a particularly large number of array elements to increase the low frequency gain.In actual engineering,the common ways to increase the gain are to reduce the sidelobe level and expand the aperture of the array,and in order to reduce the use of receiving/transmitting components,sparse technology is usually used.However,due to the non-negligible strong coupling effect of tightly coupled arrays,optimization analysis is difficult,so there is currently no literature report on the application of sparse technology to tightly coupled arrays.This paper optimizes the arrangement of tightly coupled array,and designs an ultra-wideband feeder network on this basis to reduce the use of Transmitter and Receiver(T/R)components,which effectively reduces the engineering cost and the difficulty of system implementation.The research results and innovations of this article are summarized as follows:First,this paper designs a 2～12GHz ultra-wideband tightly coupled Vivaldi antenna,which can satisfy the VSWR<2:1 when normal radiation and VSWR<3:1 when scanning 60°.Through research,it is found that by loading a resistor at the opening of the tightly coupled Vivaldi antenna to absorb part of the coupling energy,the coupling effect is optimized,which can not only achieve wide-angle matching,but also increase the radiation gain of the antenna element.In addition,this paper proposes an optimal design method for tightly coupled arrays based on unequal intervals.In order to introduce sparse technology into the ultra-wideband tightly coupled array without destroying the continuous current sheet model in the tight coupling theory,metal connecting sheets with different widths are introduced between the array elements.The unequal interval tightly coupled array makes the arrangement of the array elements more freedom,and improves the radiation performance of the array.However,the traditional optimization method based on the array factor formula ignores the coupling between the array elements,so it is no longer suitable for tightly coupled arrays.This requires an improvement in the optimization method of the array antenna.In order to achieve the rapid solution of multi-objective problems,this paper proposes a multi-objective covariance matrix adaptive evolution strategy based on decomposition(MOEA/D-CMA-ES).The advantage of this algorithm is that it combines the fast convergence characteristics of the covariance matrix adaptive evolution strategy(CMA-ES)algorithm with the characteristics of the multi-objective evolution algorithm based on decomposition(MOEA/D)that can solve multi-objective optimal solutions.In order to incorporate the unquantifiable coupling effects into the optimization process,asymptotic space mapping(ASM)is used.The MOEA/D-CMA-ES algorithm is used as the coarse model,and the full-wave analysis software is used as the fine model.The mapping relationship is constructed between the coarse and fine models,and the coupling influence is substituted into the optimization process through parameter extraction.The algorithm only needs a few iterations of mapping to get a better optimization effect and greatly improve the optimization efficiency.Apply the above-mentioned tightly coupled array optimization method based on unequal interval to 1-D linear array and 2-D area array,analyze the effect under different sparse rate,and give the full-wave simulation results and analysis of tightly coupled arrays with unequal intervals.Finally,in order to design a feeder network for the ultra-wideband unequal-spaced tightly coupled array and further reduce the sidelobe level,a 1:32 ultra-wideband unequal power divider was designed.However,because the arrays are arranged at unequal intervals,when the traditional power divider is used for feeding,the phase difference will occur due to the difference in the feeding distance,which causes the radiation direction to be deflected.Therefore,a "U"-shaped structure is innovatively proposed to adjust the feed distance and realize the synchronization of the feed phase of each port.After the design of the power divider is completed,it is loaded into the unequal interval tightly coupled array for full-wave simulation and processing test.The simulation and test results have good optimization effects.