Signal Comparing Normalized Generalized Levenshtein Distance-Based Searching Method for Modulation Period of Micro-Doppler Signal

A searching method using the signal comparing normalized generalized Levenshtein distance (SC-NGLD) as the cost function is proposed to search for the modulation period of micro-Doppler (m-D) signal. NGLD is an improved form of edit distance (also known as “Levenstein distance”) and is a commonly used distance to deal with misspelled character strings. In this paper, the string-matching-used NGLD is upgraded to SC-NGLD and is given the power of computing the differences between two numerical-signal strings. When our only propose is to obtain the modulation period of m-D signal and indicate some feature such as the heart rate and respiratory rate of a human or the rotation rate of helicopter blades, using the SC-NGLD as the cost function to search for the modulation period of m-D signal in time domain avoids the time–frequency analysis step, thus the computing burden caused by time–frequency analysis is eliminated. Besides, the proposed method has strong robustness in low pulse repetition frequency or low signal-to-noise ratio conditions. The feasibility of the proposed method is validated by processing both the simulated m-D signal and the experimental scattered signal from helicopter blade models.