CHIRP wave???
arnaud MILLE
sidescan sonar, and I want to know more about the sidescan sonar acoustic
waves.
I reallly thank you for an answer
arnaud
Angelo Campanella
>Can anybody tell me what is the chirp technology? I specially work on chirp
>sidescan sonar, and I want to know more about the sidescan sonar acoustic
In an environment containing steady frequency interferences, but that
interfering frequency can be different from time to time, one would like to
have a scheme that would avoid being troubled by that interference.
So imagine a sonar sound pulse of some duration which is at a frequency that
is continuously increased from a lower to a higher pitch. Then when
listening for the "echo", one tunes their receiver at a similarly swept
receiving frequency. The result is a reliably improved signal-to-noise ratio.
The transmitted swept signal sounds (or appears as) a "chirp.
Ang.
Sture Hulqvist
what I know...
Chirp is when you change the frequency during transmission of a burst.
By filtering the recived echo in , for example, 3 different frequencys
you can increase the SNR and mayby also the increase the time
resolution.
Normally a DSP is used but it is not neccesery by the defination.
Sture Hultqvist.
stu...@tsl.uu.se
www.tsl.uu.se/~stureh (sidescan images)
arnaud MILLE wrote:
>
> Can anybody tell me what is the chirp technology? I specially work on chirp
> sidescan sonar, and I want to know more about the sidescan sonar acoustic
Art Ludwig
> [-snip-]
> Hi I'm not so very familiar with this myself but I'll try to share
> what I know...
> Chirp is when you change the frequency during transmission of a burst.
> By filtering the recived echo in , for example, 3 different frequencys
> you can increase the SNR and mayby also the increase the time
> resolution.
>
used by radars, and is really the primary reason for chirping the
signal. Typically the frequency ramp is a linear function of time. The
radar receiver uses a local oscillator with the same frequency ramp as
the transmitted signal. The result is a narrow-band signal at a beat
frequency that is constant in time, the beat offset being directly
proportional to the delay of the returned signal. Another technique to
accomplish the same result is to transmit a maximum-length binary coded
sequence, and correlate with the same sequence in the receiver. This
technique is used by several audio measurement systems, such as CLIO.
Both techniques spread the frequency sprectrum, consistant with the fact
that the minimum obtainable time resolution is inversely proportional to
the width of the spectrum. Regards, Art Ludwig
Joe Hood
There is a considerable amount of reflections from the ocean itself
(bubbles, particles etc.) which is termed as reverberation. For moving
targets the Doppler effect separates the target reflection from the
reverberation, but for stationary or slow moving targets such as those that
bottom mapping side-scan sonars are used to detect the target reflection
frequency will remain at the same frequency as the reverberation. It then
even becomes more critical to improve range resolution and SNR for a low
Doppler 'coherent' reflector. (This is probably not the correct term, but I
do not believe that reflections due to reverberation are as consistent as
those from a reasonable target of interest. At least this is what experience
has taught me.)
My two cents.
Art Ludwig wrote in message <36891C...@silcom.com>...
Sture Hulqvist
I have only seen "Chirp" images on Datasonics homepage.
Do anyone know if there is more images somewhere?
Sture Hultqvist
Dale Chayes
> Hi again
> I have only seen "Chirp" images on Datasonics homepage.
> Do anyone know if there is more images somewhere?
I've recently put some data from the SCAMP (Seafloor Characterisation
and Mapping Pods) Highr Resolution Subbottom Profiler (HRSP) which is an
ODEC Bathy2000P. You can find the examples at:
http:/www.ldeo.columbia.edu/SCICEX/SCAMP (look for the HRSP
examples)
-Dale
arnaud MILLE
sidescan chirp sonar anywhere without datasonics, because they are the only
saler of chirp sidescan. But in marine acoustics, I know that edgetech sell
chirp seismic transciever (http://www.edgetech.com). I know too, that the
chirp has first been created for profilers (to see the first centimeters of
the sediments); so, you can search on the web at chirp profilers, but they
are majoritairely sell by datasonics.
Bye
Arnaud
Sture Hulqvist a écrit dans le message <3689F5...@tsl.uu.se>...
>Hi again
>I have only seen "Chirp" images on Datasonics homepage.
>Do anyone know if there is more images somewhere?
>
>Sture Hultqvist
>
>stu...@tsl.uu.se
>www.tsl.uu.se/~stureh
Dale Chayes
> In article <768iam$cmu$1...@front3.grolier.fr> "arnaud MILLE"
> <arno...@club-interent.fr> writes:
>
> >Can anybody tell me what is the chirp technology? I specially work on
> chirp
> >sidescan sonar, and I want to know more about the sidescan sonar
> acoustic
>
Here are a few references you might want to dig out of your local
libaray:
LeBlanc, L.R., L. Mayer, M. Rufino, S.G. Schock, and J. King, Marine
sediment classification using the chirp sonar, J. Acoust. Soc. Amer.,
1992.
LeBlanc, L.R., S. Panda, and S.G. Schock, Sonar attenuation modeling for
classification of marine sediments, J. Acoust. Soc. Amer., Jan, 1992.
Schock, S.G., and L. LeBlanc, The chirp sonar- A major advance in
subbottom profiling technology, Sea Technol., Sep, 1990.
Schock, S.G., L.R. LeBlanc, and L.A. Mayer, Chirp sub-bottom profiler
for quantitative sediment analysis, Geophysics, 54, 445-450, 1989.
-Dale