Title :
Mode equalization at megameter ranges
Author :
Chandrayadula, Tarun K. ; Wage, Kathleen E.
Author_Institution :
Dept. of Electr. & Comput. Eng., George Mason Univ., Fairfax, VA
Abstract :
Low frequency underwater sound propagation over ranges of 3.5 megameters or more has a complicated multipath arrival structure with early steep angle-arrivals, followed by an energetic finale composed of the lower order acoustic modes. Internal waves produce time-varying multipath and induce frequency-selective fading in the received signals. The low mode arrivals are strongly affected by internal waves, making it difficult to obtain precise travel time measurements for these signals. An equalizer along with suitable spatial filters, mitigates the multipath of the lower order modes. The signal to noise ratio (SNR) measured at the output of the equalizer is used as an observable to localize modes, make time of arrival (TOA) measurements and measure the multipath spread of the modes. Results for the new mode equalizer on a simulated channel are presented. The mode equalizer is also tested on one of the North Pacific Acoustic Laboratory (NPAL) receptions
Keywords :
equalisers; geophysical signal processing; multipath channels; oceanographic techniques; spatial filters; time-of-arrival estimation; underwater acoustic propagation; equalizer; frequency-selective fading; internal waves; low frequency underwater sound propagation; mode equalization; multipath arrival structure; multipath spread; signal to noise ratio; spatial filters; time of arrival measurements; time-varying multipath; Acoustic measurements; Acoustic propagation; Equalizers; Fading; Frequency; Noise measurement; Signal to noise ratio; Spatial filters; Time measurement; Underwater acoustics;
Conference_Titel :
OCEANS, 2005. Proceedings of MTS/IEEE
Conference_Location :
Washington, DC
Print_ISBN :
0-933957-34-3
DOI :
10.1109/OCEANS.2005.1639925
