Design of Generalized Sinusoidal Frequency Modulated Pulse Train Waveform to Improve Tracking Performance of High Duty Cycle Sonar Systems

Abstract

High duty cycle sonar (HDCS) systems have a high potential for improving tracking performance compared to conventional pulsed active sonar systems, but their implementation has been challenging to achieve. This is because conventional studies had focused primarily on solving direct blast interference problems caused by continuous transmission and reception of pulse train waveforms. In this paper, we propose a design scheme for a generalized sinusoidal frequency modulated (GSFM) pulse train waveform to improve HDCS tracking performance. The proposed optimization scheme utilizes the trade-off relationship between detection performance in a reverberation environment and measurement uncertainty according to the parameter ρ of the GSFM waveform. The detection probability and measurement noise covariance matrix of the Kalman filter are calculated using the HCDS tracking framework, which reflects the designed GSFM pulse train waveform in the tracking process. The simulation using the HDCS tracking framework demonstrated that optimal tracking performance was obtained when the parameter ρ was 1.07.INDEX TERMS Generalized sinusoidal frequency modulated waveform, high-duty cycle sonar system, high duty cycle sonar tracking, pulse train waveform design, I. INTRODUCTIONO VER the past few decades, research on active sonar systems have mainly focused on the pulsed active sonar (PAS) system which transmits a short pulse-type waveform with a long waiting interval when considering its maximum detection range. Due to the long waiting interval, PAS systems suffer from a low target revisit rate (TRR), which leads to a lack of measurements. Consequently, it is difficult to suppress clutter in shallow water and obtain a high tracking performance for long-range moving targets [1,2,3].Recently, the hardware of modern sonar systems have been upgraded enabling a wider dynamic range, and thus solving the problem of saturation when signals with vastly different reception levels are received [3,4]. From a geometrical perspective, modern sonar technologies show a trend towards the operation of multiple platforms and long-range detection; therefore, research on bistatic systems or multistatic sonar systems that are operated with separate transmitters and receivers is being actively conducted [5,6,7,8]. Out of these research trends, a new concept of high duty cycle sonar (HDCS) system is emerging [

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

“…Using these definitions, unlike previous studies that utilized GSFM [18], [19], [20], [21], we have substantially reduced pulse length and minimized the pulse period, which leads to a high TRR. As a result, unlike the traditional PAS, our proposed method becomes capable of tracking high-speed underwater vehicles.…”

“…Since we aim to transmit in five directions with five subpulses each, we utilize a total of 25 subpulses. The parameter search range for the GSFM is defined as shown in Table 1, which was based on the findings from Kim's study [21]. Among the 25 subpulses, the peak cross-correlation level of 10 subpulses has been provided as a sample.…”

“…Contrary to expectations, when the frequency bands of CAS were made to overlap perfectly, target detection became challenging due to DBL problem [21]. However, when the pulses were designed in the form of OBPT where only portions of the frequency bands overlapped, the system could capitalize on the clear peak of ambiguity function of GSFM while reducing the influence of DBL.…”

“…Several studies have employed the characteristics of GSFM to design CAS systems [19], [20], [21]. While theoretical analyses assured orthogonality without dividing frequency band of subpulses, experiments revealed that when the frequency bands fully overlapped, the impact of DBL becomes pronounced.…”

“…Consequently, the adoption of an overlapping band pulse train (OBPT) proved more effective for target detection [19]. Additionally, researchers pursued the optimization of GSFM parameters, namely ρ and α to design pulse trains specifically for optimal target detection and tracking [21]. Our research builds on these foundational studies, showcasing how GSFM not only enhances CAS system performance but also how our novel PAS-GSFM approach significantly outstrips traditional methods, offering rapid target detection and tracking with reduced pulse lengths without sacrificing the timebandwidth product.…”