为实现低副瓣数字阵列天线性能,需要对阵面通道幅相误差进行校准。针对此问题,定性分析了通道幅相误差、阵面通道数与数字阵列天线主要性能(副瓣电平、波束指向、增益)的相对关系,分析结果表明:通道间幅相误差越大,副瓣电平、波束指向...为实现低副瓣数字阵列天线性能,需要对阵面通道幅相误差进行校准。针对此问题,定性分析了通道幅相误差、阵面通道数与数字阵列天线主要性能(副瓣电平、波束指向、增益)的相对关系,分析结果表明:通道间幅相误差越大,副瓣电平、波束指向、增益越差;通道数越多,副瓣电平、波束指向受通道误差影响越小,而增益受通道幅相误差的影响与阵面通道数无关。结合数字阵雷达实际使用中阵面通道幅相误差修调问题,重点研究了通道误差测量方法。给出了利用内监测法和中场测量法进行通道误差测量的原理、实现方法及适用条件,该2种通道误差测量方法可以作为互补手段使用。最后,给出了一种基于多次测量取平均值的数字阵列幅相误差校准方法,仿真结果表明:校准前后,通道幅相误差分别由2 d B和20°变为0.4 d B和2°,满足指标要求。展开更多
Adopting the idea of thermal modification of conventional Si-containing eutectic alloys,this study performed heating of the brittle CoFeNi_(2)(Ti_(3)Si_(5))_(0.16) eutectic high-entropy alloy under various annealing c...Adopting the idea of thermal modification of conventional Si-containing eutectic alloys,this study performed heating of the brittle CoFeNi_(2)(Ti_(3)Si_(5))_(0.16) eutectic high-entropy alloy under various annealing conditions to attempt the fragmentation and spheroidization of eutectic microstructure and improve fracture plasticity.Results reveal that the as-cast alloy exhibited fine eutectic microstructures with lamellar+network morphologies,consisting of face-centered cubic(FCC)and M_(16)Ti_(6)Si_(7)-type silicide.After annealing at 1100℃×120 h,the lamellar+network eutectic morphologies were effectively fragmented and spheroidized into granular+irregular morphologies.The resulting alloy featured excellent mechanical properties with an ultimate compressive strength(UCS)of 1980±50 MPa,fracture plasticity of~16.6%±1%,and hardness of~448±15 HV.Compared with the as-cast specimen,the fracture plasticity of the specimen annealed for 120 h increased by 12.7 times,with no UCS reduction.With a further increase in the annealing time,the hard M_(16)Ti_(6)Si_(7)-type silicide was seriously coarsened,deteriorating the alloy’s room-temperature mechanical properties but improving its high-temperature ones.展开更多
文摘为实现低副瓣数字阵列天线性能,需要对阵面通道幅相误差进行校准。针对此问题,定性分析了通道幅相误差、阵面通道数与数字阵列天线主要性能(副瓣电平、波束指向、增益)的相对关系,分析结果表明:通道间幅相误差越大,副瓣电平、波束指向、增益越差;通道数越多,副瓣电平、波束指向受通道误差影响越小,而增益受通道幅相误差的影响与阵面通道数无关。结合数字阵雷达实际使用中阵面通道幅相误差修调问题,重点研究了通道误差测量方法。给出了利用内监测法和中场测量法进行通道误差测量的原理、实现方法及适用条件,该2种通道误差测量方法可以作为互补手段使用。最后,给出了一种基于多次测量取平均值的数字阵列幅相误差校准方法,仿真结果表明:校准前后,通道幅相误差分别由2 d B和20°变为0.4 d B和2°,满足指标要求。
基金supported by the National Natural Science Foundation of China(Grant No.U20A20278)the National Key Research and Development Program of China(Grant Nos.2019YFA0209901 and 2018YFA0702901)+1 种基金Liao Ning Revitalization Talents Program(Grant No.XLYC1807047)the Major Special Project of“Scientific and Technological Innovation 2025”in Ningbo(Grant No.2019B10086)。
文摘Adopting the idea of thermal modification of conventional Si-containing eutectic alloys,this study performed heating of the brittle CoFeNi_(2)(Ti_(3)Si_(5))_(0.16) eutectic high-entropy alloy under various annealing conditions to attempt the fragmentation and spheroidization of eutectic microstructure and improve fracture plasticity.Results reveal that the as-cast alloy exhibited fine eutectic microstructures with lamellar+network morphologies,consisting of face-centered cubic(FCC)and M_(16)Ti_(6)Si_(7)-type silicide.After annealing at 1100℃×120 h,the lamellar+network eutectic morphologies were effectively fragmented and spheroidized into granular+irregular morphologies.The resulting alloy featured excellent mechanical properties with an ultimate compressive strength(UCS)of 1980±50 MPa,fracture plasticity of~16.6%±1%,and hardness of~448±15 HV.Compared with the as-cast specimen,the fracture plasticity of the specimen annealed for 120 h increased by 12.7 times,with no UCS reduction.With a further increase in the annealing time,the hard M_(16)Ti_(6)Si_(7)-type silicide was seriously coarsened,deteriorating the alloy’s room-temperature mechanical properties but improving its high-temperature ones.
