Need help designing 2mhz PCB antenna for tiny transmitter
Shannon Bailey
I am designing a tiny Microchip PIC processor driven 2mhz transmitter
and I need help designing a 2 layer 3/4" square PCB coil and matching
network. I am hoping to redesign the existing antenna design which
uses a tiny ferrite coil and matching network. I am looking to build
the antenna right onto the PCB to save space. The range of this
antenna only needs to be six feet to a special superhetrodyne AM radio
receiver. This transmitter is part of a mouth controller for
Quadriplegic people to control their wheel chairs, TV's etc. with
their tongues. see: www.newabilities.com for more info.
I need an antenna engineer to help define the PCB coil length, wire
width, spacing and vias and create the matching network needed to load
the coil from a 3.3 volt square wave logic level drive from the PIC.
The matching network must filter off spurious harmonics producing a
clean 2mhz carrier.
I have a modest budget for this portion of the design. Please contact
me if you are interested in designing and verifying this type of
antenna.
Thanks,
Shannon Bailey
Dr. Rastis Fafoofnik
"Shannon Bailey" <sha...@simunity.com> wrote in message
news:bf158466.04091...@posting.google.com...
Why 2Mhz? the antenna won't be efficient at all, and there is a TON of noise
in that band. Why not use some of the prepackaged 433Mhz data TX/RX modules
out there...or 2.4Ghz for remote control?
Shannon Bailey
>
> Why 2Mhz? the antenna won't be efficient at all, and there is a TON of noise
> in that band. Why not use some of the prepackaged 433Mhz data TX/RX modules
> out there...or 2.4Ghz for remote control?
The short distance (18" from mouth to receiver) of the system masks
most powerful in band interference. We do experience interference
from security scanners at stores and other sources of 2mhz
interference, but the button coding scheme avoids most errors. The
guts of the whole transmitter are the size of an electronic watch
module and fit inside the persons mouth and use membrane keys for
buttons.
Several hundred existing FDA approved systems have been in use for up
to ten years using this frequency. It passes through human tissue
easily. I am engineering a replacement transmitter design for these
existing systems as the current discrete logic transmitter design is
outdated and needing replacement. I do not have the freedom to switch
frequency at this point. I am looking for an air core (or PCB
material core) coil design and matching network so I can eliminate the
current ferrite antenna from the new design to make it even smaller.
Our current antenna produces mostly inductive radiation which works
well enough in the existing transmitters to reach the receiver. I can
use the existing antenna if no PCB alternative proves sufficient. The
current antenna is a 1cm by 2x2mm square wire wrapped ferrite inductor
with about 18" of 32ga wire, a couple of surface caps and a surface
inductor form the matching network.
This is a high duty cycle application transmitter on for a total of 15
minutes or more per day. A dime cell powered design at 433mhz would
require much too much power and has poor human body penetration
characteristics. Other frequencies (from 7mhz through 150mhz) are now
being authorized for use in through body communication to pacemakers
and synthetic organs. We may switch to a somewhate higher frequency
for a next generation design but for now must make a compatible 2mhz
PCM transmitter to provide ongoing support for the existing systems.
Anyway, if you can help provide antenna and matching network design
software or antenna consulting for this project please contact me. We
probably have thought about most other options and weighed the issues
which include new FDA and FCC certification and regulation issues.
Thanks for your consideration,
Shannon Bailey
Dr. Rastis Fafoofnik
Perhaps you may want to consider an IR emitter? it can be made small enough,
good on power, will have the range you need......just a thought. select a
high enough "carrier" freq and it wont be bothered by lighting or other apps
nearby.
Shannon Bailey
I am looking for an engineer capable of designing a 2mhz 3/4" square
PCB antenna. It can be very inefficient but still must work as well
as possible within the constraints I've specified. Referals would be
great too.
Knowledgable HAMS who can breadboard the design and have sufficient
test gear to verify it are also welcome to contact me. I will provide
a small signal generator circuit for testing.
Thanks,
Shannon