The low angle tracking problem was investigated for shipborne X-band array radar working at frequency diversity mode.Firstly,the receiving array signal model with multi-frequency was established in multi-path environment based on the relation between complex reflection coefficient (CRC)and grazing angle of seawater at X band.Then,the research put forward the MFML (Multi-Frequency Maximal Likelihood) elevation spectrum,in which the elevation ambiguity is alleviated by frequency diversity.The spacing between spectrum peaks was presented.The influence on elevation spectrum of frequency width was analyzed.Lastly,the probability of exact peak selection was proposed to describe the elevation estimation performance.Elevation estimation performance was evaluated by simulation,related to SNR and target elevation.Given target elevation,the minimal SNR was obtained for a certain angular accuracy,which is not strictly monotone downtrend with target elevation.%针对舰载X波段阵列雷达研究了低角跟踪问题，雷达工作在频率分集模式。利用复反射系数与擦地角的关系建立了多频多径条件下阵列接收信号模型。推导了多频极大似然仰角谱，揭示了多频体制抑制仰角模糊的机理，推导出了仰角谱栅瓣间隔，分析了系统带宽对仰角谱的影响。提出谱峰正确选择概率来度量测角性能，通过仿真研究了SNR、目标仰角对仰角谱估计精度的影响，给定目标仰角条件下得到了满足测角精度要求的最小SNR，最小SNR随目标仰角增加并非严格单调下降。
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