On Tuesday, October 13, 2015 at 11:01:43 AM UTC-4, Randy Yates wrote:
> N0Spam@daqarta.com (Bob Masta) writes:
>
> > On Mon, 12 Oct 2015 13:49:27 -0400, Randy Yates
> > <yates@digitalsignallabs.com> wrote:
> >
> >>Consider the fundamental concept of a sonar (or radar) hich transmits a
> >>pulse and is looking for the return.
> >>
> >>Are there targets which significantly distort the pulse shape, so that
> >>using a simple correlation (matched filter) for the detector results in
> >>degraded performance?
> >>
> >>In other words, it seems like what you REALLY want to use is a return,
> >>or received, signal correlator, not a transmit signal correlator. Of course that
> >>would require knowledge of the "target transfer function" H(w), so that
> >>what you are correlating against is R(w) = T(w)H(w).
> >>
> >>Other than a difference in the possible expected H(w)'s, are there any
> >>differences in this problem for a radar versus a sonar?
> >>
> >>Thoughts?
> >>--
> >>Randy Yates
> >>Digital Signal Labs
> >>http://www.digitalsignallabs.com
> >
> > Dunno, but I wonder if the field of medical ultrasound would
> > be a good place to look for info. Seems like these issues
> > must come up there all the time, and though I haven't looked
> > I would guess there might be more publications available:
> > Hot field, and no security restrictions.
>
> Thanks, Bob. As it turns out, this is an ultrasound application. I don't
> know much more - just looking at an abbreviated job description.
> --
> Randy Yates
> Digital Signal Labs
> http://www.digitalsignallabs.com
Ultrasound usually gets generated via piezoelectric transducers - those are high Q with narrow bandwidth around resonance frequency.
You simply don't get much of w change.
So this is not it.
There are tons of other effects: target shape or texture, multi-path, clutter etc
You need to provide more details to get some answers
Reply by Randy Yates●October 13, 20152015-10-13
N0Spam@daqarta.com (Bob Masta) writes:
> On Mon, 12 Oct 2015 13:49:27 -0400, Randy Yates
> <yates@digitalsignallabs.com> wrote:
>
>>Consider the fundamental concept of a sonar (or radar) hich transmits a
>>pulse and is looking for the return.
>>
>>Are there targets which significantly distort the pulse shape, so that
>>using a simple correlation (matched filter) for the detector results in
>>degraded performance?
>>
>>In other words, it seems like what you REALLY want to use is a return,
>>or received, signal correlator, not a transmit signal correlator. Of course that
>>would require knowledge of the "target transfer function" H(w), so that
>>what you are correlating against is R(w) = T(w)H(w).
>>
>>Other than a difference in the possible expected H(w)'s, are there any
>>differences in this problem for a radar versus a sonar?
>>
>>Thoughts?
>>--
>>Randy Yates
>>Digital Signal Labs
>>http://www.digitalsignallabs.com
>
> Dunno, but I wonder if the field of medical ultrasound would
> be a good place to look for info. Seems like these issues
> must come up there all the time, and though I haven't looked
> I would guess there might be more publications available:
> Hot field, and no security restrictions.
Thanks, Bob. As it turns out, this is an ultrasound application. I don't
know much more - just looking at an abbreviated job description.
--
Randy Yates
Digital Signal Labs
http://www.digitalsignallabs.com
Reply by Bob Masta●October 13, 20152015-10-13
On Mon, 12 Oct 2015 13:49:27 -0400, Randy Yates
<yates@digitalsignallabs.com> wrote:
>Consider the fundamental concept of a sonar (or radar) hich transmits a
>pulse and is looking for the return.
>
>Are there targets which significantly distort the pulse shape, so that
>using a simple correlation (matched filter) for the detector results in
>degraded performance?
>
>In other words, it seems like what you REALLY want to use is a return,
>or received, signal correlator, not a transmit signal correlator. Of course that
>would require knowledge of the "target transfer function" H(w), so that
>what you are correlating against is R(w) = T(w)H(w).
>
>Other than a difference in the possible expected H(w)'s, are there any
>differences in this problem for a radar versus a sonar?
>
>Thoughts?
>--
>Randy Yates
>Digital Signal Labs
>http://www.digitalsignallabs.com
Dunno, but I wonder if the field of medical ultrasound would
be a good place to look for info. Seems like these issues
must come up there all the time, and though I haven't looked
I would guess there might be more publications available:
Hot field, and no security restrictions.
Best regards,
Bob Masta
DAQARTA v8.00
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
Frequency Counter, Pitch Track, Pitch-to-MIDI
FREE 8-channel Signal Generator, DaqMusiq generator
Science with your sound card!
Reply by kevinjmcee●October 12, 20152015-10-12
On Monday, October 12, 2015 at 4:05:22 PM UTC-4, rickman wrote:
> On 10/12/2015 3:58 PM, Randy Yates wrote:
> > rickman <gnuarm@gmail.com> writes:
> >
> >> On 10/12/2015 1:49 PM, Randy Yates wrote:
> >>> Consider the fundamental concept of a sonar (or radar) hich transmits a
> >>> pulse and is looking for the return.
> >>>
> >>> Are there targets which significantly distort the pulse shape, so that
> >>> using a simple correlation (matched filter) for the detector results in
> >>> degraded performance?
> >>>
> >>> In other words, it seems like what you REALLY want to use is a return,
> >>> or received, signal correlator, not a transmit signal correlator. Of course that
> >>> would require knowledge of the "target transfer function" H(w), so that
> >>> what you are correlating against is R(w) = T(w)H(w).
> >>>
> >>> Other than a difference in the possible expected H(w)'s, are there any
> >>> differences in this problem for a radar versus a sonar?
> >
> > Hey Rick,
> >
> > Thanks for your thoughts.
> >
> >> I was never well versed in SONAR, but I do remember there are
> >> dispersive effects that distort a pulse shape. One of the effects is
> >> just reverb where some of the transmitted signal bounces back from the
> >> medium itself. I would expect your filter might want to compensate
> >> for the distortion, but that would need to be function of distance
> >> which could be substituted for by time.
> >
> > Yeah, but even if you knew time/distance, how would you know what to
> > compensate?
> >
> >>
> >> I guess the question is, just how significant is the distortion? I
> >> don't recall any of the sub systems using such a filter, but like I
> >> said, I wasn't in that job long enough to learn much.
> >
> > Was it a sonar or radar?
>
> SONAR. I was thinking active. Otherwise what pulse would you be
> working with? With active you know the time of flight and from that can
> get a good value for range. I would expect the pulse distortion to be
> fairly constant possibly only varying a bit with temperature. A lot of
> SONAR word is relatively constant temperature because the sounds bounce
> off thermal layers and travel almost like in a waveguide.
>
> Subs have their own assumptions about environments. What exactly is
> your environment?
>
> Rereading your question, you are asking about distortion from the
> target. I can't say I've ever considered that or seen where anyone else
> did. But as I said, my experience was short and some 20+ years ago.
>
> --
>
> Rick
> rickman <gnuarm@gmail.com> writes:
>
>> On 10/12/2015 1:49 PM, Randy Yates wrote:
>>> Consider the fundamental concept of a sonar (or radar) hich transmits a
>>> pulse and is looking for the return.
>>>
>>> Are there targets which significantly distort the pulse shape, so that
>>> using a simple correlation (matched filter) for the detector results in
>>> degraded performance?
>>>
>>> In other words, it seems like what you REALLY want to use is a return,
>>> or received, signal correlator, not a transmit signal correlator. Of course that
>>> would require knowledge of the "target transfer function" H(w), so that
>>> what you are correlating against is R(w) = T(w)H(w).
>>>
>>> Other than a difference in the possible expected H(w)'s, are there any
>>> differences in this problem for a radar versus a sonar?
>
> Hey Rick,
>
> Thanks for your thoughts.
>
>> I was never well versed in SONAR, but I do remember there are
>> dispersive effects that distort a pulse shape. One of the effects is
>> just reverb where some of the transmitted signal bounces back from the
>> medium itself. I would expect your filter might want to compensate
>> for the distortion, but that would need to be function of distance
>> which could be substituted for by time.
>
> Yeah, but even if you knew time/distance, how would you know what to
> compensate?
>
>>
>> I guess the question is, just how significant is the distortion? I
>> don't recall any of the sub systems using such a filter, but like I
>> said, I wasn't in that job long enough to learn much.
>
> Was it a sonar or radar?
SONAR. I was thinking active. Otherwise what pulse would you be
working with? With active you know the time of flight and from that can
get a good value for range. I would expect the pulse distortion to be
fairly constant possibly only varying a bit with temperature. A lot of
SONAR word is relatively constant temperature because the sounds bounce
off thermal layers and travel almost like in a waveguide.
Subs have their own assumptions about environments. What exactly is
your environment?
Rereading your question, you are asking about distortion from the
target. I can't say I've ever considered that or seen where anyone else
did. But as I said, my experience was short and some 20+ years ago.
--
Rick
Reply by Randy Yates●October 12, 20152015-10-12
rickman <gnuarm@gmail.com> writes:
> On 10/12/2015 1:49 PM, Randy Yates wrote:
>> Consider the fundamental concept of a sonar (or radar) hich transmits a
>> pulse and is looking for the return.
>>
>> Are there targets which significantly distort the pulse shape, so that
>> using a simple correlation (matched filter) for the detector results in
>> degraded performance?
>>
>> In other words, it seems like what you REALLY want to use is a return,
>> or received, signal correlator, not a transmit signal correlator. Of course that
>> would require knowledge of the "target transfer function" H(w), so that
>> what you are correlating against is R(w) = T(w)H(w).
>>
>> Other than a difference in the possible expected H(w)'s, are there any
>> differences in this problem for a radar versus a sonar?
Hey Rick,
Thanks for your thoughts.
> I was never well versed in SONAR, but I do remember there are
> dispersive effects that distort a pulse shape. One of the effects is
> just reverb where some of the transmitted signal bounces back from the
> medium itself. I would expect your filter might want to compensate
> for the distortion, but that would need to be function of distance
> which could be substituted for by time.
Yeah, but even if you knew time/distance, how would you know what to
compensate?
>
> I guess the question is, just how significant is the distortion? I
> don't recall any of the sub systems using such a filter, but like I
> said, I wasn't in that job long enough to learn much.
> On Mon, 12 Oct 2015 13:49:27 -0400, Randy Yates
> <yates@digitalsignallabs.com> wrote:
>
>>Consider the fundamental concept of a sonar (or radar) hich transmits a
>>pulse and is looking for the return.
>>
>>Are there targets which significantly distort the pulse shape, so that
>>using a simple correlation (matched filter) for the detector results in
>>degraded performance?
>>
>>In other words, it seems like what you REALLY want to use is a return,
>>or received, signal correlator, not a transmit signal correlator. Of course that
>>would require knowledge of the "target transfer function" H(w), so that
>>what you are correlating against is R(w) = T(w)H(w).
>>
>>Other than a difference in the possible expected H(w)'s, are there any
>>differences in this problem for a radar versus a sonar?
>>
>>Thoughts?
>
> It's been a long time since I worked on radar, but this was never an
> issue when I did, i.e., you always correlated against the Tx pulse.
> If you are expecting or detecting Doppler, that has to be accounted
> for, but I don't think that's what you're asking about.
>
> Sonar has other things to deal with, like dispersion due to
> thermoclines, etc., and I think there are countermeasures that are
> acoustically absorptive and maybe even frequency selective.
> Consider the fundamental concept of a sonar (or radar) hich transmits a
> pulse and is looking for the return.
>
> Are there targets which significantly distort the pulse shape, so that
> using a simple correlation (matched filter) for the detector results in
> degraded performance?
>
> In other words, it seems like what you REALLY want to use is a return,
> or received, signal correlator, not a transmit signal correlator. Of course that
> would require knowledge of the "target transfer function" H(w), so that
> what you are correlating against is R(w) = T(w)H(w).
>
> Other than a difference in the possible expected H(w)'s, are there any
> differences in this problem for a radar versus a sonar?
I was never well versed in SONAR, but I do remember there are dispersive
effects that distort a pulse shape. One of the effects is just reverb
where some of the transmitted signal bounces back from the medium
itself. I would expect your filter might want to compensate for the
distortion, but that would need to be function of distance which could
be substituted for by time.
I guess the question is, just how significant is the distortion? I
don't recall any of the sub systems using such a filter, but like I
said, I wasn't in that job long enough to learn much.
--
Rick
Reply by Eric Jacobsen●October 12, 20152015-10-12
On Mon, 12 Oct 2015 13:49:27 -0400, Randy Yates
<yates@digitalsignallabs.com> wrote:
>Consider the fundamental concept of a sonar (or radar) hich transmits a
>pulse and is looking for the return.
>
>Are there targets which significantly distort the pulse shape, so that
>using a simple correlation (matched filter) for the detector results in
>degraded performance?
>
>In other words, it seems like what you REALLY want to use is a return,
>or received, signal correlator, not a transmit signal correlator. Of course that
>would require knowledge of the "target transfer function" H(w), so that
>what you are correlating against is R(w) = T(w)H(w).
>
>Other than a difference in the possible expected H(w)'s, are there any
>differences in this problem for a radar versus a sonar?
>
>Thoughts?
It's been a long time since I worked on radar, but this was never an
issue when I did, i.e., you always correlated against the Tx pulse.
If you are expecting or detecting Doppler, that has to be accounted
for, but I don't think that's what you're asking about.
Sonar has other things to deal with, like dispersion due to
thermoclines, etc., and I think there are countermeasures that are
acoustically absorptive and maybe even frequency selective.
Eric Jacobsen
Anchor Hill Communications
http://www.anchorhill.com
Reply by Randy Yates●October 12, 20152015-10-12
Consider the fundamental concept of a sonar (or radar) hich transmits a
pulse and is looking for the return.
Are there targets which significantly distort the pulse shape, so that
using a simple correlation (matched filter) for the detector results in
degraded performance?
In other words, it seems like what you REALLY want to use is a return,
or received, signal correlator, not a transmit signal correlator. Of course that
would require knowledge of the "target transfer function" H(w), so that
what you are correlating against is R(w) = T(w)H(w).
Other than a difference in the possible expected H(w)'s, are there any
differences in this problem for a radar versus a sonar?
Thoughts?
--
Randy Yates
Digital Signal Labs
http://www.digitalsignallabs.com