Re: am transmitter - vlsi project

To get back to the poor original poster's question, and to point out
some POSITIVE and realistic options, instead of all our poo-poohing:

If you want to make a transmitter, a really small one, one that can
actually broadcast some distance more than a few millimeters, and
still be detectable over the background noise:

(1) Think hard about the physics of the antenna situation-- a tiny
antenna implies a HIGH frequency. For instance, if your "dust" is
going to be on the order of an IC chip size, the frequency, in order to
have a 1/4 wave antenna, is going to have to be in the tens of
gigahertzs region.

(2) I suspect your vlsi process is not up to building gigahertz-region
digital frequency synthesizers. It may be capable of low-gig
rizetimes, but for a true synthesizer you'd need at least 20 times the
output frequency to make effective synthesizer components, like adders
and D/A's.

(3) Also think about the power situation-- even if your vlsi is
low-power (which it won't be at GHz sppeds), a transmitter will need
several milliwatts of ouput power to overcome background noise level,
and that requires several times the input milliwatts.-- figure out how
large a battery or solar cell has to be to generate a few milliwatts
for even a few seconds.
Prolly a whole lot larger than ic-size.


(4) Also think about the rules of your country's FCC. In the USA you
can't just broadcast willy-nilly, there are specific bands and emission
modes required (I think, unless there's some loophole). As far as I
know, you have to stick to 100mw or so max power, and in the AM or FM
bands, or around 13.56MHz, or twice that, or the 47 and 4xx MHz old
wireless phone bands, or the microwave 2.6 GHz band, or a few other
narrow spots. And I suspect you have to do AM in the AM band, FM in
the FM band.

Just a suggestion, but the choices seem to narrow to:

VLSI digital synthesizer for the AM BC band, but with a long antenna
(up to 3 meters in the USA).

VLSI analog synthesizer in the FM band, with a several inch antenna.

IC analog oscillator/modulator in the 4xx or 2.6 GHzMHz band, with an
inch or so of antenna.

... and for power source, the tinyiest of lithium hearing-aid batteries,
so I hope your VLSI process can run on 1.5 or 3 volts :)

Hope this helps.

.

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