Robust Active Sonar Detection in Frequency and Time Dispersive Channels Using Matching Envelope Spectrum of Multi-Pulse LFM Signals

Abstract

For detecting the target echoes undergoing distortion in frequency and time dispersive channels, a novel robust active sonar detector is proposed. The proposed active detector firstly extracts the matching envelope (ME) of the multi-pulse linear frequency modulation (LFM) signals, and then the peaks of the matching envelope spectrum (MES) contained in the designed grid searching windows are detected. The grid searching windows are designed based on the theoretical analysis of the features of the MES. Lastly, the detector utilizes the detected peaks to make a judgement for determining whether there are target echoes existing in the received signal. In addition, the proposed detector can be applied to detect the multipulse single frequency target echoes. The proposed active detector shows a more stable performance in the frequency and time dispersive channels, compared to several classical methods, including the replica correlation (RC), the segmented RC (SRC), and the RC integration (RCI) detectors. Simulation results validate the improved performance of the active detector, showing a gain of 0.5-4 dB compared with more standard state-of-the-art detectors. Experimental results based on sea trial data have also verified the validity and feasibility of the proposed active detector. INDEX TERMS Active sonar detection, fast-fading distortion (FFD), matched filter, matching envelope spectrum (MES), time-spreading distortion (TSD)

Identical code‐data cyclic shift transmission for time‐dispersive channel

“…and h 2 d (3) . All three paths are resolvable in this scenario, providing six copies of the transmitted data for combining.…”

“…The MFB produces a data stream d (0) along with its cyclic shifts d (1) , d (2) and d (3) . The cyclic shifting was applied to each MFB output corresponding to an individual path, aligning the data from different paths.…”

“…2 Signal detection in fading environments is a significant challenge in modern systems with wide bandwidths. 3 Researchers have been investigating how signals evolve over time and exploring more effective methods for signal detection under various conditions. 4,5 Enhanced approaches for signal detection and straightforward transmission techniques have been introduced.…”

“…This fading phenomenon can occur abruptly, even over short distances 2 . Signal detection in fading environments is a significant challenge in modern systems with wide bandwidths 3 . Researchers have been investigating how signals evolve over time and exploring more effective methods for signal detection under various conditions 4,5 .…”

Pulsed Active Sonar Using Generalized Sinusoidal Frequency Modulation for High-Speed Underwater Target Detection and Tracking

“…They are indispensable devices for acquiring data about moving targets in underwater environments and are critical for tasks ranging from detecting potential threats in naval operations to identifying fish schools in commercial ventures. Based on their operating principles, these systems can be broadly divided into passive and active sonar [1], [2], [3], [4], [5], [6].…”