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I need to generate ultrasound with a frequency of 1.5 MHz. The ultrasound should be pulsed as shown here

enter image description here

An ultrasound pulse should be 200 µs long, a pause (no ultrasound) is 800 µs long. The desired intensity should be 30 mW/cm^2 and upwards.

The problem is, I have no idea where I would even start. I have basic to advanced theoretical knowledge of electronics and physics, I have soldered once, but that's about it.

So I need you for guidance :).

What device do I need to generate the ultrasound? I guess a normal speaker won't do.

What do I have to do to generate such a pulse form and the desired frequency?

What other items do I need?

I prefer pre-built components (like an ultrasound generator which can give me the above pulse form and frequency) over having to build everything myself; but if I have to build something myself, I'll take on the challenge and hopefully learn something from it.

Any thoughts or pointers are greatly appreciated.

(If my question is too broad, I'll be happy to provide more details.)

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  • \$\begingroup\$ What will this be used for? \$\endgroup\$ – MadHatter Nov 19 '15 at 15:10
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Ultrasonic transducers are used for several applications on boats.

Alas, I haven't seen any tuned for exactly 1.5 MHz, but perhaps a transducer tuned to some slightly different higher or lower frequency will be adequate for your application:

Parsonics "14 kHz to 4.5 MHz"

Airmar "4.5 MHz"; Airmar "30 kHz to 300 kHz"

NKE Marine "4.5 MHz"

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I think your best option for this frequency is to look a medical ultrasound transducer. Places like BK Precision make them but they will be expensive. Here is an 1.5MHz option from a unknown supplier on Alibaba that may be suitable for your application, though you may want to ask about a datasheet, or at the very least instructions for driving it properly.
As far as pulsing goes, a transistor switch with a microcontroller (or even e.g. 555 timer) to could be easily set up to control things.

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  • \$\begingroup\$ Thank you. I should probably add that I do not need to receive any ultrasound that is bounced back. Just emitting is fine. Medical ultrasound transducers seem to be overprized for this purpose. Isn't there a cheaper option? \$\endgroup\$ – Fahrenheit64 Sep 2 '11 at 1:11
  • \$\begingroup\$ Not sure, alomost certainly cheaper than the BK options, but the Alibaba one probably won't be too unreasonable (what price range are you looking for?) Another option might be the ones used in ultrasonic cleaning apparatus. As they are not so common the price will probably reflect that (although 40-100kHz ones are widely/cheaply available) I would check on Digikey, Mouser, Farnell, RS, etc, maybe ask in the help channels available as they may be able to source them if not in stock, or direct to to a reliable source. \$\endgroup\$ – Oli Glaser Sep 2 '11 at 1:36
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Generation and receiving of ultrasound at that frequency is done with a piezoelectric transducer. Look up CZT or Quarts. It may be challenging as the frequency your looking for is medical, not the low frequency ~40khz used in fishing and range finders... You said you do not need to receive, that makes it a lot less complex, receiving ultrasound of that frequency is not an easy task. You may find some ultrasound IC chips for receiving, basically fancy ADC, but the generation will probably need to be all custom.

Someone mentioned a 555, that would work OK but gives harmonics due to the fact that you are driving the transducer with square waves, really for a clean signal you would want a sinusoidal 1.5Mhz, unless your transducer is selective.

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