低信噪比条件下基于距离像互相关的相推测速方法

相推测速技术可以实现相位量级的测量精度,在微动测量和目标识别领域有着极大的应用前景。该方法对信噪比要求较高,且存在准确提取相位和解相位模糊两大难点。本文提出了针对低信噪比条件下的相推测速实现方法。首先,建立了宽带线性调频信号去斜处理的回波模型;然后推导了相邻帧距离像互相关结果,并分析了距离像互相关输出的峰值点相位;进而为了提高相推测速在低信噪比条件下的适用性,提出了对距离像互相关结果沿慢时间维进行积累的方法,该方法可以重新提取峰值点相位,以及获得目标速度的粗估计值进而辅助后续的解相位模糊。此外,为抑制噪声对相位提取精度的影响,本文提出根据相位的频谱特性设计滤波器的方法,进一步提高相推测速的精度。最后通过仿真和实测数据验证了所提方法的正确性及其在低信噪比条件下的适用性。 

A Phase-Derived Velocity Measurement Method based on Range Profiles Cross Correlation under Low SNR

Phase-derived velocity measurement (PDVM) can achieve phase level measurement accuracy, thus has a great application prospect in the field of micromotion feature extraction and target recognition. The PDVM method requires high signal-to-noise ratio (SNR), and the keys of PDVM method are accurate phase extraction and resolving phase ambiguity. In this paper, a PDVM method based on range profiles cross correlation (RPCC) under low SNR condition is proposed. Firstly, a wideband linear frequency modulation (LFM) signal echo model of dechirp processing is established. Then, the RPCC results of adjacent frames are derived, and the peak position phases of the RPCC results are analyzed. After that, in order to improve the applicability of PDVM under low SNR conditions, a method is proposed to accumulate the RPCC results along the slow time dimension. This method can re-extract the peak position phases and obtain the coarse estimate of target velocity, which enables to assist in the subsequent phase ambiguity resolving processing. In addition, in order to suppress the influence of noise on the extracted phase, a filter design method based on the phase spectral characteristics is proposed, so as to further improve the accuracy of PDVM. Finally, the validity of the proposed method and its applicability under low SNR are verified by simulation and experiment.