Researches On Aperiodic Antenna Arrays With Wide-angle Scanning Performance

The main goal of wide-angle scanning phased arrays is to broaden the scanning coverage with other basic array characteristics unchanged.Planar wide-angle scanning phased arrays have powerful advantages in modern military and civil application fields due to their wide angular field of view.Many published designs of the wide-angle scanning phased array are mainly realized with special element antennas,such as wide-beam and joint wide-beam antennas.Based on the traditional principle of pattern multiplication,the array factor is also an important part to determine the array performance besides the element factor.In order to further enhance the beam scanning performance,this dissertation will focus on the design of wide-angle scanning phased array from array element design to array structure design,and the main contents are introduced as follows.Chapter 1 mainly gives a summary of several design methods of wide-angle scanning phased arrays and their technical challenge.Meanwhile,the concept of wide-angle scanning phased arrays with an aperiodic array structure is introduced.The research actuality of the aperiodic array,the advantages of the aperiodic array,and the problems of the wide-angle scanning phased array combined with the aperiodic structure are also presented in this chapter.Chapter 2 mainly introduces three designs of special element antennas and their periodic wide-angle scanning phased arrays.In the three designs,a new design method for the wide-angle scanning phased array is proposed and designs of phased arrays are transformed from one-dimensional arrays to two-dimensional ones.Firstly,based on the mode theory,a dual-mode pattern reconfigurable antenna and its wide-angle scanning phased array are designed.In this design,the number of reconfiguration modes becomes less and thus the design complexity is reduced.Then,two designs,which are respectively based on parasitic pixel-layer elements and pattern-reconfigurable windmill-shaped loop elements,are presented.The both designs are able to obtain wide-angle scanning range in both E-and H-planes.Therefore,the design of two-dimensional wide-angle scanning phased arrays is realized.Chapter 3 mainly studies the analysis and synthesis methods of aperiodic arrays.According to the four different processing methods for mutual coupling effects inaperiodic arrays,several corresponding array analysis and synthesis methods and techniques are proposed.Firstly,for some ultra-large planar arrays,the mutual coupling between array elements is often negligible.And in this case a novel hybrid algorithm based on the multi-objective genetic algorithm and iterative fast Fourier transform technique is proposed for large planar array thinning.Secondly,the radiation patterns of large arrays can be transformed from the superposition of element patterns to the product of the array factor and the element factor through the mutual coupling compensation method.Then an improved iterative fast Fourier transform technique based on the mutual coupling compensation matrix is proposed in this dissertation,and it can be used for the design of large time-modulated arrays.Thirdly,mutual coupling effects in small-scale arrays can be considered by predicting or calculating.In this situation,an array thinning method based on the method of exhaustion of subarray active element patterns is proposed.This method is able to take the element coupling into consideration in the analysis and synthesis of aperiodic arrays.At last,in small-scale arrays,mutual coupling effects can also be elimilated by means of mutual coupling suppression.An isolation enhancement method using a polarization-conversion isolator,which can dramatically realize the reduction of mutual coupling between microstrip antennas,is proposed.Chapter 4 presents two aperiodic phased arrays with wide-angle scanning performance based on the analysis and synthesis methods and special elements for the wide-angle scanning phased arrays mentioned in the above two chapters.In the first design,wide-coverage and low-sidelobe performance of a wide-angle scanning phased array is obtained through the cancellation principle of the subarray nulls and array factor grating lobes.The second conformal phased array is based on pattern reconfigurable antenna elements.The phased array is able to support quasi-full-space scanning beams.Chapter 5 makes a comprehensive summary of the full dissertation,and it points out the issues needed to be further researched.