pic microcontroller discussion list <> wrote on Saturday, June 21, 2003
5:28 PM:

> That said:   The overall project has to do with underwater
> communications, using transducers.  I have been told that the purer
> the tone driving the transducer, the more efficient it would be, and
> so figured that a sine wave would be better to drive it with than a
> square wave would be.  So the original query was basically:  "How
> hard it is to convert a square wave to a sine wave?"

How limited is the transmitter?  If there is no shortage of power, and the
amplifier and transducers can cope with the heat generated, I would
probably go for a lowpass filter and a simple differential pseudo-sine
wave, use two outputs so you can generate +5/0/-5.  It depends on even more
specs (!!!), like how much power is available, what the comms channel
(vertical or horizontal, type of water) is like etc.  I, and others on the
list, have some experience in underwater comms (several km in a 30m
channel, a couple of 100km in deep water with some fairly heavy duty DSP),
so if you are able to reveal more about your application, someone here
_might_ be able to save you quite a lot of duplicated effort and some
not-so-obvious 'gotchas'.

Nigel
--
Nigel Orr, Design Engineer                 nigel@axoninstruments.co.uk
Axon Instruments Ltd., Wardes Road,Inverurie,Aberdeenshire,UK,AB51 3TT
               Tel:+44 1467 622332 Fax:+44 1467 625235
                   http://www.axoninstruments.co.uk

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