Fast Synthesis Algorithms For Large-scale Antenna Arrays

Array antennas have been widely used in military,aerospace,aviation,medicine and other fields.With the development of science and technology,there are more and more requirements for array radiation characteristics.Large-scale array plays an important role in 5G communications because of its high radiation gain and high beam resolution.Iterative Fourier Transform(IFT)has been proved to be efficient in the synthesis of large arrays,but it is limited to the array whose elements are laid out on rectangular grids.What is more,the thinned array synthesis based on IFT relies too much on the random initial excitations,which results in low efficiency.When the element spacing is far less than half wavelength,IFT would be affected by the data in the invisible region,thus the robustness of the synthesis algorithm is poor.To solve the above problem,this paper proposes an iterative Chirp-z algorithm and an iterative segmented fast convolution method,which breaks the limitation of array layout,making the efficient synthesis of circular array and even cylindrical array possible.The iterative Chirp-z also overcomes the shortcomings in thinning array,improves the robustness,and expands its application to large-scale arrays with minimum spacing control.Firstly,the array synthesis including traditional IFT algorithm and the proposed iterative Chirp-z algorithm is introduced,which is only applicable to arrays with elements on rectangular grids.Because the traditional IFT algorithm is affected by the element spacing,it is necessary to complement and truncate the array pattern samples when synthesizing.The proposed iterative Chirp-z overcomes the above shortcomings because of its flexible spiral calculation method.Especially when the element spacing is far less than half-wavelength,its advantages would be outstanding.Consider:ing the array with elements laid out on circular ring,an iterative segmented fast convolution(ISFC)is proposed in this paper.By using the consistency of the circular array pattern formula and the fast convolution,the evaluation of uniform circular array patterns is accelerated.What is more,combined with FFT,ISFC is also extended to the efficient calculation of the separable cylinder array.Several synthetic examples are used to verify the effectiveness of the algorithm.Finally,aiming at the shortcomings of IFT in thinned array synthesis,an modified iterative FFT and an modified iterative Chirp-z algorithm are proposed.Through a large number of experiments,it is concluded that the modified IFT is not only more efficient,but also can obtain lower sidelobes and narrower beams under the same constraints,and the modified iterative Chirp-z algorithm can also effectively control the minimum spacing of the array elements.Both of the two modified algorithm have great practical value.