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Hi-Spec Systems
we are specialised in the design, development and manufacture of Phased Array and Time-of-Flight Diffraction (ToFD) ultrasonic inspection systems.
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Career Discussions
Richard
Richard
01:25 Oct-08-2003
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





 
 Reply 
 
Linas Svilainis
R & D,
Kaunas University of Technology, Lithuania, Joined Nov 1998, 67

Linas Svilainis

R & D,
Kaunas University of Technology,
Lithuania,
Joined Nov 1998
67
02:34 Oct-08-2003
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




 
 Reply 
 
Joerg Schulze-Clewing
Joerg Schulze-Clewing
09:59 Oct-08-2003
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 ------------




 
 Reply 
 
Richard
Richard
00:32 Oct-09-2003
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 ------------




 
 Reply 
 
Linas Svilainis
R & D,
Kaunas University of Technology, Lithuania, Joined Nov 1998, 67

Linas Svilainis

R & D,
Kaunas University of Technology,
Lithuania,
Joined Nov 1998
67
02:46 Oct-10-2003
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




 
 Reply 
 

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