SYSTEM AND METHOD OF RANGE ESTIMATION
A system and method of range estimation are disclosed. In one embodiment, the method comprises transmitting beams through a medium towards a surface, receiving reflected signals from the surface, and estimating range to the surfaced based on the reflected signals and an estimate of sidelobe coupling of the beams.
1 . A method of estimating a distance to a surface of a body of water, the method comprising:
receiving signals reflected from the surface of the body of water, the reflected signals corresponding to two or more beams, wherein one of the reflected signals comprises at least a main component corresponding to a selected one of the beams and a sidelobe component corresponding to another of the beams, and wherein the sidelobe component interferes with the main component;
generating compensated data by applying a linear transformation on data indicative of the one of the reflected signals to at least partly remove the sidelobe component; and
estimating the distance to the surface of the body of water based on the compensated data.
2 . The method of claim 1 , wherein the linear transformation comprises generating at least one weighted sum based on data indicative of the received reflected signals.
3 . The method of claim 1 , wherein the linear transformation comprises subtracting an estimate of the sidelobe component from the data indicative of the one of the reflected signals.
4 . The method of claim 1 , wherein the surface of the body of water is a bottom surface of the body of water.
5 . The method of claim 1 , further comprising transmitting an acoustic pulse from a transducer oriented so as to reflect the transmitted acoustic pulse from a bottom surface of the body of water, wherein received reflected signals comprise an echo of the transmitted acoustic pulse.
6 . The method of claim 1 , wherein generating the compensated data is based on an a priori estimate of the sidelobe component.
7 . The method of claim 1 , further comprising replacing values of the compensated data that are below a threshold with a specified value.
8 . The method of claim 1 , further comprising:
convolving the compensated data with a detection filter to produce a convolved signal;
locating a highest peak on the convolved signal; and
comparing the highest peak to a threshold;
wherein estimating the distance is based on said comparing.
9 . The method of claim 1 , wherein receiving comprises receiving reflected signals corresponding to four beams via transducers, wherein each of the four beams corresponds to a beam transmitted from the transducers in a Janus configuration.
10 . A range estimation system relating to transmission and reception of acoustic signals in a fluid medium, the system comprising:
a sonar system having a plurality of transducers configured to generate respective acoustic beams and to receive echoes from the acoustic beams, wherein one of the received echoes comprises at least a main component corresponding to a selected acoustic beam and a sidelobe component corresponding to at least one other of the acoustic beams, and wherein the sidelobe component interferes with the main component; and
a range estimation module configured to estimate a distance based on data indicative of the received echoes and an estimate of sidelobe coupling of the at least one other of the acoustic beams with the selected acoustic beam.
11 . The system of claim 10 , wherein the system is embodied in an acoustic Doppler current profiler.
12 . The system of claim 10 , wherein the estimate of sidelobe coupling comprises an a priori estimate of sidelobe coupling.
13 . The system of claim 10 , wherein the transducers are arranged in a Janus configuration.
14 . The system of claim 10 , further comprising a sidelobe compensation module configured to apply a linear transformation to the data indicative of the received echoes, wherein the range estimation module is configured to estimate the distance based on the linear transformation.
15 . A non-transitory computer-readable storage medium comprising:
a sidelobe compensation module comprising instructions executable by at least one processor to process data indicative of echoes of pings transmitted by transducers through a body of water, and generate compensated data by performing a linear transformation on the data indicative of echoes to remove an estimate of sidelobe coupling of a selected one of the echoes to at least one other of the echoes from the data indicative of echoes; and
a range estimation module comprising instructions executable by at least one processor to compute a range based on the compensated data generated by the sidelobe compensation module.
16 . The non-transitory computer-readable storage medium of claim 15 , wherein the linear transformation comprises subtracting the estimate of the sidelobe coupling from at least a portion of the data indicative of echoes.
17 . The non-transitory computer-readable storage medium of claim 15 , wherein the linear transformation comprises summing weighted versions of the data indicative of echoes.
18 . The non-transitory computer-readable storage medium of claim 15 , wherein the sidelobe compensation module further comprises instructions executable by at least one processor to replace values of the compensated data that are below a threshold with a specified value.