Range Resolution Enhancement using Root-MUSIC Analysis in CTFM Sonar for Bandwidth-limited Applications

ABSTRACT This paper presents a detailed study of the application of Root-MUSIC algorithm in the continuous-time frequency modulation (CTFM) system. Classically, CTFM-based sonars and radars use the Discrete Fourier transform (DFT) magnitude peaks to find the range of the received echoes. In applications where the medium does not support large signal bandwidth over the ranges of interest, the DFT technique cannot provide the required range resolution. A technique called dual demodulator continuous-time frequency modulation (DDCTFM) was proposed to overcome this limitation and provides greater range resolution. But we observe that there is a problem of phase mismatch in DDCTFM that does not increase the range resolution. This problem is explained in the paper. The super resolution Root-MUSIC algorithm is studied in this context to evaluate its efficacy in providing higher frequency resolution and corresponding range resolution in CTFM. Several detailed simulation experiments done in MATLAB to provide insight into its performance are reported in the paper. Also, lab experiments have been done to practically demonstrate the efficacy of using Root-MUSIC technique in CTFM. Based on the results obtained from the simulation experiments, it is concluded that there is an improvement by a factor of 2.8 in the range resolution estimation by the use of Root-MUSIC algorithm over DFT-based analysis in CTFM. In practical experiments, the improvement factor obtained in the range resolution estimation is 2.35.

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