An Introduction to Sonar Systems Engineering

The book discusses various theories and applications of underwater acoustic communication, including beamforming, array theory, and signal design. It also covers bistatic scattering and target detection in reverberation and noise.

Format: Hardback
Length: 747 pages
Publication date: 23 August 2022
Publisher: Taylor & Francis Ltd

The theory of arrays encompasses a wide range of topics, including linear, planar, and volume array theory. It delves into the analysis of near-field and far-field beam patterns, beam steering, and array focusing. One significant aspect of array theory is the twin-line planar array, which is a solution to the port/starboard (left/right) ambiguity problem commonly encountered in linear towed arrays. This ambiguity arises when the array elements are positioned along a line rather than in a grid. The twin-line planar array consists of two parallel lines of elements, each with a different orientation, allowing for the differentiation of signals coming from different directions.

Another important topic in array theory is the linear array of triplets. This array configuration is designed to mitigate the port/starboard ambiguity problem by incorporating three elements in each direction. By combining the signals from these three elements, the ambiguity is resolved, and the direction of arrival of a target can be accurately determined.

Side-looking (side-scan) and synthetic-aperture sonars are two other applications of array theory. Side-looking sonars employ a narrow beam to scan a large area horizontally, providing a comprehensive view of the surrounding environment. Synthetic-aperture sonars, on the other hand, use a collection of individual sensors to create a virtual aperture, allowing for high-resolution imaging and target detection.

Signal design is a crucial aspect of array theory, particularly in underwater acoustic communication signals. CW (continuous-wave), LFM (low-frequency modulation), and HFM (high-frequency modulation) pulses are commonly used for range and Doppler estimation. These signals are designed to transmit information over long distances and through water, with varying degrees of accuracy depending on the pulse shape and frequency content.

Underwater acoustic communication signals also include MFSK (modified frequency-shift keying), MQAM (quadrature amplitude modulation), and OFDM (orthogonal frequency-division multiplexing). MFSK is a simple and robust modulation technique that is widely used in underwater communication systems. MQAM, on the other hand, offers higher data rates and better resistance to noise compared to MFSK. OFDM, meanwhile, is a popular modulation technique used in wireless communication systems and has been adapted for underwater communication applications.

Bistatic scattering is a phenomenon that occurs when a sound source emits acoustic waves toward a target, and the target reflects or scatters the waves back to the source. This process can be analyzed using the principles of array theory, particularly in the context of moving platforms. Derivations of exact solutions for the time delay, time-compression/time-expansion factor, and Doppler shift at a receiver for both the scattered and direct acoustic paths can be obtained. These solutions are essential for understanding the behavior of bistatic scattering and its impact on underwater acoustic communication systems.

Target detection in the presence of reverberation and noise is another important topic in array theory. Reverberation is the reflection of acoustic waves from surfaces and objects in the underwater environment, while noise is the random variation in acoustic signals caused by various sources. Both reverberation and noise can significantly degrade the performance of underwater acoustic communication systems. Target detection algorithms, such as matched filter algorithms, can be used to mitigate the effects of reverberation and noise and improve the accuracy of target location.

In conclusion, array theory plays a vital role in the analysis and design of various applications in acoustics, including underwater acoustic communication. The twin-line planar array, linear array of triplets, side-looking and synthetic-aperture sonars, signal design, underwater acoustic communication signals, bistatic scattering, and target detection are just a few of the topics covered in this field. By understanding the principles of array theory, researchers and engineers can develop more efficient and effective acoustic systems for a wide range of applications.

Weight: 1580g
Dimension: 254 x 178 (mm)
ISBN-13: 9781032190037
Edition number: 2 ed