The waveguide invariant in shallow water environments has been widely studied in the context of passive sonar. The invariant provides a relationship between the frequency content of a moving broadband source and the distance to the receiver, and this relationship is not strongly affected by small perturbations in environment parameters such as sound speed or bottom features. Recent experiments in shallow water suggest that a similar range-frequency structure manifested as striations in the spectrogram exists for active sonar, and this property has the potential to enhance the performance of target tracking algorithms. Nevertheless, field experiments with active sonar have not been conclusive on how the invariant is affected by the scattering kernel of the target and the sonar configuration (monostatic vs bistatic). The experimental work presented in this paper addresses those issues by showing the active invariance for known scatterers under controlled conditions of bathymetry, sound speed profile and high SNR. Quantification of the results is achieved by introducing an automatic image processing approach inspired on the Hough transform for extraction of the invariant from spectrograms. Normal mode simulations are shown to be in agreement with the experimental results.

1.
S. D.
Chuprov
, “
Interference structure of a sound field in a layered ocean
,” in
Ocean Acoustics. Current State
, edited by
L. M.
Brekhovskikh
and
I. B.
Andreeva
(
Nauka
,
Moscow
,
1982
), pp.
71
91
.
2.
L. M.
Brekhovskikh
and
Y. P.
Lysanov
,
Fundamentals of Ocean Acoustics
, 3rd ed. (
Springer
,
New York
,
2002
), Chap. 6, pp.
118
143
.
3.
D.
Rouseff
and
R. C.
Spindel
, “
Modeling the waveguide invariant as a distribution
,” in
Ocean Acoustic Interference Phenomena and Signal Processing
, edited by
W. A.
Kuperman
and
G. L.
D’Spain
(
AIP
,
New York
,
2002
), Chap. 5, pp.
137
148
.
4.
D.
Rouseff
and
C. V.
Leigh
, “
Using the waveguide invariant to analyze lofargrams
,” in
Proceedings of the Oceans ‘02
, Biloxi, MS (
2002
), pp.
IV
2239
IV
2243
.
5.
G. L.
D’Spain
and
W. A.
Kuperman
, “
Application of waveguide invariants to analysis of spectrograms from shallow water environments that vary in range and azimuth
,”
J. Acoust. Soc. Am.
106
,
2454
2468
(
1999
).
6.
T. C.
Yang
, “
Beam intensity striations and applications
,”
J. Acoust. Soc. Am.
113
,
1342
1352
(
2003
).
7.
A.
Thode
, “
Source ranging with minimal environmental information using a virtual receiver and waveguide invariant theory
,”
J. Acoust. Soc. Am.
108
,
1582
1594
(
2000
).
8.
L. M.
Zurk
and
B. H.
Tracey
, “
Depth-shifting of shallow water waveguide source observations
,”
J. Acoust. Soc. Am.
118
,
2224
2233
(
2005
).
9.
J. E.
Quijano
,
L. M.
Zurk
, and
D.
Rouseff
, “
Demonstration of the invariance principle for active sonar
,”
J. Acoust. Soc. Am.
123
,
1329
1337
(
2008
).
10.
J.
Turgut
and
R.
Gauss
, “
Investigation of bistatic invariance principles for active sonars
,”
J. Acoust. Soc. Am.
125
,
2704
2704
(
2009
).
11.
C.
He
,
J. E.
Quijano
, and
L. M.
Zurk
, “
Enhanced Kalman filter algorithm using the invariance principle
,”
IEEE J. Ocean. Eng.
34
,
575
585
(
2009
).
12.
R.
Goldhahn
,
G.
Hickman
, and
J. L.
Krolik
, “
Waveguide invariant reverberation mitigation for active sonar
,” in
IEEE International Conference on Acoustics, Speech and Signal Processing
, Honolulu, HI (
2007
), pp.
II
941
II
944
.
13.
L. M.
Zurk
,
D.
Rouseff
,
J. E.
Quijano
, and
G.
Greenwood
, “
Bistatic invariance principle for active sonar geometries
,” in
Proceedings of the 8th European Conference on Underwater Acoustics ‘06
, Carvoeiro, Portugal (
2006
), pp.
787
791
.
14.
J. S.
Rogers
and
J. L.
Krolik
, “
A study of active sonar reverberation using ultrasonic experiments in a shallow-water tank
,” in
Proceedings of the Oceans ‘07
, Scotland, UK (
2007
), pp.
1
5
.
15.
K. D.
LePage
,
P.
Neumann
and
C. W.
Holland
, “
Broad-band time domain modeling of sonar clutter in range dependent waveguides
,” in
Proceedings of the Oceans ‘06
, Boston, MA (
2006
), pp.
1
5
.
16.
T.
Oesterlein
,
C.
He
,
J. E.
Quijano
,
R.
Campbell
, Jr.
,
L. M.
Zurk
, and
M.
Siderius
, “
Extraction of time-frequency target features
,” in
Conference Record of the 39th Asilomar Conference on Signals, Systems and Computers ‘09
, Pacific Grove, CA (
2009
).
17.
F. B.
Jensen
,
W. A.
Kuperman
,
M. B.
Porter
, and
H.
Schmidt
,
Computational Ocean Acoustics
, 1st ed. (
Springer-Verlag
,
New York
,
2000
), Chap. 5, pp.
257
281
.
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