A SOLUTION OF WIDEBAND HOPPING FOR ACTIVE UNDERWATER NAVIGATION SYSTEMS

Abstract

Active underwater navigation systems have mostly used single pulse modulation signals of the sine, cosine, hyperbolic, or linear frequency modulation in recent years. These systems using the signals are limited factors such as range resolution, low azimuth; bad anti-interference ability; the maximum detection distance is not large and it is not possible to ensure the secrecy of the transmitted signal structure. This paper presents a new broadband signal solution using Costas code to improve detection and resolution capabilities for active underwater navigation systems. The research proposes a model of frequency hopping hydroacoustic signal according to the Costas rule and signals combining Costas frequency hopping with linear frequency modulation, applied on the active sonar model of ultra-short baseline USBL. Simulation results show that the discriminant ability of the navigation system depends only on the bandwidth of the signal, gain of the signal to noise ratio at the output of the combined filter is 17 dB with the Costas N=8 and 23.8 dB with Costas N=16. This result allows the design of longer signal chains to improve activity range of the sonar system while ensuring high resolution at range.