Research On The Wide-band Large-angle Active Phased Array Antenna

The conventional active phased array radar has many advantages,but due to the limitation of the aperture fill time and beam pointing drift,it is difficult for conventional phased array radar to get wide instantaneous bandwidth under large scan scope,which limits its applications in the field of wide-band and ultra-wide-band.In recent years,wide-band and large-angle active phased array becomes a hot spot in the research of radar technology,it uses the method of real-time delay to offset the aperture fill time,so that it can be used in wide-band even ultra-wide-band radar beam forming and processing.The wide-band and large-angle active phased array is the system of shared-aperture and large airspace scanning,it can identify and track multi-function radar system.Associated tightly to a "Research on frequency response characteristics of phased array with wide instantaneous bandwidth" pre-research project,this dissertation presents a systematic investigation on the analysis and design of the wide-band and large-angle antenna,and array is discussed emphatically.The factors of bandwidth limitation and the effects of receive channels phase and amplitude fluctuation on array are analyzed in theory.The author's major contributions on the subject can be summarized as follows:1.Two types of wide-band and large-angle antenna elements:multi-layer aperture slot coupled microstrip antenna and new vivaldi antenna,are studied.The design of UWB antenna is guided by Q factor theory,a variety of methods are used to improve the bandwidth of the antenna,by adding metallized vias around the patch,the surface-wave propagation along the medium is suppressed,the radiation efficiency of the antenna could be increased;by filling high permittivity materials in the array,the array could scan in E-plane and H-plane.The antennas have the advantages of high gain,ultra-wide-band,symmetrical radiation beam,low profile,light weight,easy processing and so on.It can be widely used in wide-band phased array antenna system;2.Multi-objective unequally-spaced array synthesis based on the modified differential evolution algorithm is investigated.The modified differential evolution algorithm(MDE),which employs the simplified quadratic interpolation algorithm and adaptively adjusts the parameter crossover probability factor(CR)and mutation strategy,is presented.Benchmark functions have been provided to verify the performance of the MDE.Then the unequally-spaced linear array is optimized by the MDE.Numerical results reveal that the peak side-lobe level and the peak side-band level of optimized array are much lower,and the MDE can optimized the unequally-spaced array faster and better;3.Based on the layered scheme of real-time delay line applied in the sub-array of the wide-band phased array,a method to optimize quantization errors of real-time delay line is proposed.Through randomizing time-delay in the sub-array,the beam pointing drift is improved with little gain losses and more compact antenna system.Besides,a new layered scheme of real-time delay line in the wide-band phased array antenna is researched,compared with the real-time delay line applied to elements or sub-array,the scheme with proper ratio of long-time delay line and short-time delay line,can not only provide the excellent correction performance of beam-pointing drift,but also easier to actualize;4.Based on the principle of frequency response characteristic of wide-band and large-angle phased array antenna,a mathematical simulation model of the system is established.According to the experimental data,a more accurate simulation model is obtained after the iterative correction.The amplitude and phase frequency characteristics of the measured array system are revised in the radar system and the imaging test is done;5.The influence of radome on the frequency response of antenna array is analyzed,and a double-layer active frequency selective surface(AFSS)radome suitable for wide-band and large-angle scanning array antenna is studied.The AFSS is composed of frequency selective surface(FSS),PIN diode array and DC feeder network.By adjusting the bias current of diode array,the transmission characteristics of AFSS can be dynamically adjusted to achieve switch switching,and the simulation and test results under different polarization and different incident angles are given.