Hi,
I am new to ultrasonic simulation, and I am kind of curious how you guys decide to generate a tone burst by multiply a series of sinusoidal signals and Gaussian distribution function. I would really appreciate if you can provide me some literatures about that. Thanks.
Hi george020106,
Conventional ultrasound transducers are typically made from piezoelectric ceramics with a backing layer and quarter-wave matching layer. The mechanical and electrical response of these systems means that they can only efficiently generate sound waves over a particular range of frequencies (they are essentially resonant devices). This range is characterised by the centre frequency and Q-factor or fractional bandwidth of the transducer. In practice, the resonant behaviour means the generated sound waves will resemble a tone burst, even when excited by an impulse. A gaussian is just one way of approximating the envelope of such a signal.
Hope that helps,
Brad.
Hi Brad,
Appreciate for your input, and I think I am kinda clear about the mechanism of the ultrasonic wave generation with piezoelectric sensors. I also understand that a Gaussian function is used to shape a series of sinusoidal signals to generate a tone-burst. What I am interested is why use Gaussian function, and are there any papers can support that. You know, when I quote your approach in my paper, I cannot simply write: I think it is a good way to generate the envelope the signal...
Previously I usually use my experimental data of ultrasonic wave as excitation source in my simulation, and I think your way to generate a signal is much more simple. Really hope your rich experience could enlighten me. Thanks.
I appreciate your point! I can't think of a good reference of the top of my head. I will ask around and see if anyone has something in mind.
Brad.
Hi george020106,
As Brad said in his reply, the shape of the pulse envelope will depend on the transducer bandwidth. Often the ring up and ring down are a few cycles each for a fairly broadband piezoceramic transducer. I don't have a specific reference but it is a fairly commonly used approximation. As you have experimental data then you can verify if this is true in your case.
For toneburts of longer than a few cycles a guassian envelope is not very suitable. For many transducers there will be a ring up time which could be up to 8 to 10 cycles in some cases and a ring down of a few cycles at the end (depending on how resonant the transducer is) with a stable amplitude in between. There is some discussion of this in the literature and International standards (IEC 62556 on HITU field characterisation) related to HIFU transducers. You could look up the following references, I'm sure there are others also:
Khokhlova et al. 2013 J. Acoust. Soc. Am. 134 (2); 1586.
Jenderka and Wilkens. 2012 Metrologia, 49 (2012) S275–S278.
There will be an updated version of the toneburst function in the next release to allow you to choose the number of ring up and ring down cycles or change the shape of the envelope.
Elly
Dear Elly and Brad,
Your replies really help me a lot. I am familiar with some of the literatures you provide, and I will read the rest of them. About the standard, I didn't find that one. I think you might refer to the code of IEC TS 62556? I will read that one, too.
Thanks again for your help, you guys are wonderful.
George
Hi George,
Yes sorry that was a typo, you are right it is IEC 62556.
Glad it's useful.
Elly
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