Publication Date:
2022-05-25
Description:
Submitted in partial fulfillment of the requirements for the degree of Master of Science at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution August 1989
Description:
In this thesis, a new active sonar imaging concept is explored using the principle
of code-division and the simultaneous transmission of multiple coded signals. The signals
are sixteen symbol, four-bit, non-linear, block Frequency-Shift Keyed (FSK)
codes, each of which is projected into a different direction. Upon reception of the reflected
waveform, each signal is separately detected and the results are inverted to yield
an estimation of the spatial location of an object in three dimensions. The code-division
sonar is particularly effective operating in situations where the phase of the transmitted
signal is perturbed by the propagation media and the target Most imaging techniques
presently used rely on preservation of the phase of the received signal over the dimension
of the receiving array. In the code-division sonar, spatial resolution is obtained by
using the combined effects of code-to-code rejection and the a-priori knowledge of
which direction each code was transmitted. The coded signals are shown to be highly
tolerable of phase distortion over the duration of the transmission. The result is a high-resolution,
three-dimensional image, obtainable in a highly perturbative environment
Additionally, the code-division sonar is capable of a high frame rate due to the simplicity
of the processing required. Two algorithms are presented which estimate the spatial
coordinates of an object in the ensonified aperture of the system, and the performance of
the two is compared for different signal to noise levels. Finally, the concept of code-division
imaging is employed in a series of experiments in which a code-division sonar
was used to image objects under a variety of conditions. The results of the experiments
are presented, showing the resolution capabilities of the system.
Keywords:
Sonar
;
Remote sensing
;
Imaging systems
Repository Name:
Woods Hole Open Access Server
Type:
Thesis
Format:
application/pdf
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