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01:25 Oct-08-2003
Richard
Re: bathymetric transducer construction

Dear Linas and others, it's clearer, better now, it's my question which was wrongly formulated, because indeed I don't completely understand the pulse 'thing.'

But i know now that one measurement from the transducer, or in my case transducer array, (one depth scan from a stroke on the bottom)is in fact a pulse burst(pulse duration)and has many pulses in it.

I also ment to ask if a longer pulse burst(pulse duration or pulse length)exciting from the same central frequency has broather bandwith, because a short pulse has (contains) more frequenties, but a short pulse burst (duration) with many pulses has also a broader bandwidth?

Quote
"One can state that increasing the "burst" length amplitude will increase. But only up to the limit of 1/(transducer bandwith). Then it will stay constant."

So Pulse length = 1/bandwidth (?)

Best regards,
Richard





 
02:34 Oct-08-2003

Linas Svilainis

R & D,
Kaunas University of Technology,
Lithuania,
Joined Nov 1998
67
Re: bathymetric transducer construction Dear Richard,

one last comment:
You wrote:
: So Pulse length = 1/bandwidth (?)

If it's single pulse-yes.
But most probably you mean "burst".
In such case it's twice:
1/Pulse length = 2 x bandwidth
or
Pulse length = 1/bandwidth /2

Bearing this in mind one can assume that amplitude stabilisation, increasing the "burst" duration would occure at 1/bandwidth /2.
Actually complete stabilisation occurs at 1/bandwidth...

good luck

Linas

Actual ampli




 
09:59 Oct-08-2003
Joerg Schulze-Clewing
Re: bathymetric transducer construction As Linas said, bandwidth decreases proportionately to the
increase in burst length.

But this may be ok depending on what you want to do. As an
example: Medical ultrasound scanners pulse their arrays
with a very short burst of typically 2-3 pulses to obtain
the best bandwidth, which in turn yields the best
resolution. But when penetration is called for, like scanning
a really heavy patient, longer bursts may be required.
When even more signal to noise ratio is called for such as
in color flow imaging (to visualize blood flow) the burst
lengths are set much longer, sacrificing a lot of
bandwidth. That is because resolution is mostly less
important than being able to see the signal when doing
flow analysis.

Regards, Joerg.

----------- Start Original Message -----------
: Dear Richard,
: one last comment:
: You wrote:
: : So Pulse length = 1/bandwidth (?)
: If it's single pulse-yes.
: But most probably you mean "burst".
: In such case it's twice:
: 1/Pulse length = 2 x bandwidth
: or
: Pulse length = 1/bandwidth /2
: Bearing this in mind one can assume that amplitude stabilisation, increasing the "burst" duration would occure at 1/bandwidth /2.
: Actually complete stabilisation occurs at 1/bandwidth...
: good luck
: Linas
: Actual ampli
------------ End Original Message ------------




 
00:32 Oct-09-2003
Richard
Re: bathymetric transducer construction Yes, I mean puls burst, I found out it's a Pulse Continuous Wave =PCW, so like you said before; a CW.
And a CW contains many pulses with a peak of energie at the center frequentie. (?)

They talk about gated CW, what do they mean by gated?

So then;
pulselength = 1/(0.5*bandwidth).

Bandwidth * pulselength ~ 1
should be approximately 1 I read somewhere.

Thank you,
Richard

----------- Start Original Message -----------
: Dear Richard,
: one last comment:
: You wrote:
: : So Pulse length = 1/bandwidth (?)
: If it's single pulse-yes.
: But most probably you mean "burst".
: In such case it's twice:
: 1/Pulse length = 2 x bandwidth
: or
: Pulse length = 1/bandwidth /2
: Bearing this in mind one can assume that amplitude stabilisation, increasing the "burst" duration would occure at 1/bandwidth /2.
: Actually complete stabilisation occurs at 1/bandwidth...
: good luck
: Linas
: Actual ampli
------------ End Original Message ------------




 
02:46 Oct-10-2003

Linas Svilainis

R & D,
Kaunas University of Technology,
Lithuania,
Joined Nov 1998
67
Re: bathymetric transducer construction Hello Richard,

: They talk about gated CW, what do they mean by gated?
CW means CONTINUOUS wave. Then, if you need it of some length, you have to "cut" a piece of it. Othrerword - gate it. So, gated CW=burst

: Bandwidth * pulselength ~ 1
: should be approximately 1 I read somewhere.
Actualy this equation should contain word equivalent.
Furthermore this product is not 1 for complex signals, for instance Chirp or PhaseCodedBurst

Good luck
Linas




 


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