shaped burst

[jan.didden]

Hi guys,

I have been looking for a signal/function generator that could output a shaped tone burst as in the attachment.
Surprisingly, although almost all have a tone burst capability, I have not found a single one that could window or filter the burst. Many have window functions like Hanning or Bartlett, but apparently only as a wave shape to output, not to filter a generated signal.

Am I looking for unobtanium? (I know you can generate such signals offline with for instance a spreadsheet, and upload to the test equipment, but I specifically wanted a native hardware capability).

Grateful for any pointers!

Jan

 

[billshurv]

Any AFG should do it. Was trying to find what SL used as he was a fan of those, but remembering where it was hidden on linkwitz labs site is stressing the grey matter!


EDIT: found it Test signal

 

[jan.didden]

Follow-up: although AP specifically mentions that their (modulated) burst signal always starts and stops immediately, creating large bandwidth spurious signals, actually it is more subtle like that.

You can use the DSP in the AP 2722 to generate a shaped burst! So apparently my problem has a solution, although I still would like to know if a stand-alone signal/function generator exists that can do it too ...

Jan

 

[billshurv]

SL gives you the expression for Goldwave to generate the function if that helps.

 

[JohnPM]

REW's tone burst generator is fairly flexible, but not a standalone solution of course.

 

[phofman]

REW can generate a single burst with amplitude window. I did not find the cosine envelope among the many offered, but John would likely add one if a use case was shown.

Edit: Too late

 

[jan.didden]

This was what I got from the AP.

Jan

 

[jan.didden]

REW's tone burst generator is fairly flexible, but not a standalone solution of course.

Of course! I should have thought about that, this also is a very flexible option. More flexible than the AP actually, which has, as far as I can see, no selectable windowing.

I need it as a test signal for my 2kV direct drive amp for ESLs, I am too chicken to apply full signal right away ;-)

Jan

 

[as_audio]

Name of the original JAES Linkwitz article with an easy build for a shaper like this is "Shaped Tone Burst Testing".

 

[as_audio]

JAES papers

 

[jan.didden]

Yes, known paper. Too much obsolete chips involved ;-)
Rod Elliot has a similar implementation, inspired by Siegfried.
This stuff has enough parts to build a medium sized nuclear reactor

Jan

 

[trobbins]

I need it as a test signal for my 2kV direct drive amp for ESLs, I am too chicken to apply full signal right away ;-)

I've been using REW's tone burst function recently, for output stage valve amp testing - applying just a few sine pulses avoids red-plating and other stresses (such as my ears if I have a speaker connected) - just need a digital scope for plot capture.

 

[as_audio]

Yes, known paper. Too much obsolete chips involved ;-)


Jan

I own one.

 

[phofman]

Or storing the REW burst to wav/flac and playing when needed from a phone. Many phones have excellent audio output.

 

[1audio]

You could lash two function generators together if one has an AM capability. Some vintage generators have that ability internally. A similar burst was used in analog video testing, which may be where Sig originally got the idea.

 

[jan.didden]

I have a simple dual channel function generator but couldn't get it to do what I wanted.
But between the AP and REW with my trusted Focusrite soundcard, I'm all set.

That is what I like on this forum - you just talk about something and you get ideas and thinking points and before you know it, your problem is solved! Thanks guys.

Jan

 

[gpapag]

Hi Jan
This classic among the cheap ebay DDS has two preset waveforms that may suit you. A sinc pulse (Pre 6) and an amplitude modulated one (Pre 9), both freq and amplitude adjustable from the front panel controls.
Then you can ampl modulate one output from the other, or draw a 2048 points arbitrary waveform (through the SW and a USB connected pc)

George

 

[jan.didden]

George, that looks good, but I have a question. This waveform is continuous, right? I need it to be a burst of some cycles, followed by a blank period.
I don't think that is possible this way. Probably is possibly offline.

Jan

 

[gpapag]

Yes, it's continuous.
For a single waveform, you have to build it through the SW and load it in one of the four memory slots (ARB1 TO ARB4) of the instrument. After downloading, the pc connection is not needed.

George

 

[1audio]

Could you set it to run one cycle of the burst and use the other channel to trigger the burst at arbitrary rates?