Re: [SI-LIST] : Spread spectrum project

Pat Zabinski (zabinski.patrick@mayo.edu)
Tue, 12 Oct 1999 06:43:42 -0500

Dave,

This would be a significant senior project, but "doable" if
you have the drive and support.

There are several direct sequence and frequency hopping
spread spectrum (DSSS and FHSS) component available on
the commercial market (e.g., Harris), and they will get you
quite far along. However, even though they provide the
microcontroller and correlators, there is still much
algorithm writing to be done. If you're well versed in
communication and SS theory, then it's simply a matter
of applying what you know. If you're a bit weak in this
area, I suggest looking for a slightly less agressive
project.

In terms of propogation, antenna size, and such, these
are generally quite simple and straight forward calculations
done by hand or with a spread sheet. In addition to
a link budget (specifying all gain and loss elements
starting from the modulator all the way through the
to the demodulator), you'll need to use Friis transmission
formula to determine the loss/gain between antennas.

I'd recommend you thoroughly read and understand at least
Chapters 1, 2, and 4 of Stutzman and Thiele, Antenna Theory
and Design, to learn more. They're easy reading and
will give you an idea of just how simple/complicated the
propogation issues are.

A few issues you're likely to run up against that are
not generally covered in undergraduate course are:

* multipath
* phase noise
* noise parameters
* SS digital correlators
* SS microcontroller algorithms

With brute-force engineering (i.e., over-kill), you can overcome
the first three with a little luck, but the last two require
a bit of knowledge if you're going to be successful.

Before signing up, I recommend you perform a thorough web search
for existing components to see what's out there. If you can
simply purchase an existing wireless link, then you've got it
made. If you need to develop the link from scratch, it might
be more than you've bargined for.

Enjoy,
Pat

> Subject: [SI-LIST] : Spread spectrum project
> Hi
>
> I'm going into my 4th (final) year of a B. Eng
> (Aerospace/Avionics). One of the projects I'm
> considering is a 2.4-2.6GHz spread spectrum system.
> The system cannot output more than 5W, and will be
> used primarily for digital video transmission. It may
> be necessary in the future for this system to transmit
> multiple data streams (ie video, telemetry, control).
> The project also requires the design and construction
> of patch antennae for the Tx and Rx. I have two
> questions.
> Firstly, does this project appear reasonable? There
> are other, easier projects available for me to do if
> this is too difficult, or unlikely to be finished in
> time.
> Secondly, if I do decide to do it, what sort of
> problems am I likely to encounter? Just general
> things like propagation, track width, antenna size
> etc.
>
> Any help is greatly appreciated
>
> Dave
>

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