Greetings,

I'm currently developing a project which requires a specialized
antenna. The system consists in a sensor equipped suit that delivers
the data to a server. I'm having problems findind a suitable antenna
for the suit, since it requires to be integrated on the suit or in a
backpack (whip antennas are out of the question, since the suit can't
have any holes). The main problem is the human body effect and the
size constraints. Gain is also a major requirement since the range of
the operations will be 400 meters with line of sight.
(Server side: 10 dBm Tx Power and a 6 dB whip antenna, Suit side: -96
dBm sensibility- freq:433 MHz)

I've tried a patch antenna (similar to the one provided by linx
technologies) but it didn't perform well. I've also tried a small whip
antenna but the ground plane dimensions aren't suitable for
integrating this type of antennas in the backpack. I've also found a
dipole body worn antenna ( http://www.panorama.co.uk )., but I'm not
sure of its performance. Currently I'm trying to develop my own
antenna, which consists of a pcb small loop antenna. I'm asking for
sugestions and maybe antenna references for this type of application.

Thanks in advance.

Greetings,

I'm currently developing a project which requires a specialized
antenna. The system consists in a sensor equipped suit that delivers
the data to a server. I'm having problems findind a suitable antenna
for the suit, since it requires to be integrated on the suit or in a
backpack (whip antennas are out of the question, since the suit can't
have any holes). The main problem is the human body effect and the
size constraints. Gain is also a major requirement since the range of
the operations will be 400 meters with line of sight.
(Server side: 10 dBm Tx Power and a 6 dB whip antenna, Suit side: -96
dBm sensibility- freq:433 MHz)

I've tried a patch antenna (similar to the one provided by linx
technologies) but it didn't perform well. I've also tried a small whip
antenna but the ground plane dimensions aren't suitable for
integrating this type of antennas in the backpack. I've also found a
dipole body worn antenna ( http://www.panorama.co.uk )., but I'm not
sure of its performance. Currently I'm trying to develop my own
antenna, which consists of a pcb small loop antenna. I'm asking for
sugestions and maybe antenna references for this type of application.

Thanks in advance.


I am not aware of any publicly available info that would aid you on this. There
are paths to solutions, but you won't find them on a radio amateur NG.

73,
Chip N1IR

On 22 Dec 2004 03:53:39 -0800, (icelord) wrote:

(whip antennas are out of the question, since the suit can't
have any holes).

Hi OM,

I don't see what holes have to do with your problem unless the suit is
not of fabric but made of laminar plastic, say (very uncomfortable if
so).

The main problem is the human body effect and the
size constraints. Gain is also a major requirement since the range of
the operations will be 400 meters with line of sight.
(Server side: 10 dBm Tx Power and a 6 dB whip antenna, Suit side: -96
dBm sensibility- freq:433 MHz)

Size is not much of a constraint (for a dipole size of 34 cM). 400
meters is not that far for 10dBm (neglecting the "6 dB whip antenna").
Sensitivity suggests you can tolerate 106 dB path loss which would not
be found in 400 meters distance (about 80dB path loss, less with "6 dB
whip antenna"). This leaves something like 20 to 30dB headroom before
you consider body proximity and its attendant loss.

I've also found a
dipole body worn antenna ( http://www.panorama.co.uk )., but I'm not
sure of its performance.

It is simple enough to build and test certainly. There is absolutely
nothing remarkable about it, and the molded plastic T contains only
wire connections of the two conductors (coax) coming to it. Given
your constraints, you don't have much choice in how it performs. If
it doesn't work, you will have to move either the suit closer to your
server, or the server closer to the suit (or increase
power/sensitivity).

Currently I'm trying to develop my own
antenna, which consists of a pcb small loop antenna. I'm asking for
sugestions and maybe antenna references for this type of application.

A small loop is not going to give you gain and putting it on a PCB is
not a solution with any advantage. Such claims to the contrary
(should you encounter them in the marketplace) are merely advertising
hyperbole with no particular merit. The dipole your link leads to is
the common reference against which all antennas are compared to and
any loss suffered by its proximity to the body will be suffered by all
others equally from the identical problem.

If this loss is intolerable, you must put some distance between it and
the body, but aside from your "pack," you have painted such solutions
out of the picture through your constraints.

As an aside. Your biggest problem will be with multi-path reception.
The problem here is multiple reflections between and around the two
antennas that will cancel the signal through any movement of your suit
across a quarter wavelength (17 cM or so). This could be a mild
problem, or it could be severe, or it could go unnoticed. This is all
a function of reflective surfaces within that same range. The
solution is multiple antennas performing in what is called "space
diversity." Research this term as a key phrase in combination with
the key word antenna. The rules are very simple and still within your
implementation.

73's
Richard Clark, KB7QHC

In article ,
(Fractenna) wrote:


I am not aware of any publicly available info that would aid you on this.
There
are paths to solutions, but you won't find them on a radio amateur NG.

73,
Chip N1IR

What's this? Are you telling us that the "Fantastic Fractal Antenna"
isn't the solution to this, and, or all the worlds problems?????
How can this be?? I was under the impression that the "Fantastic
Fractal Antenna" was thr "Cats Meow" and could solve all our problems.



Me who wonders if the Sky will now Fall, or Hell Has Frozen Over....

What's this? Are you telling us that the "Fantastic Fractal Antenna"
isn't the solution to this, and, or all the worlds problems?????
How can this be?? I was under the impression that the "Fantastic
Fractal Antenna" was thr "Cats Meow" and could solve all our problems.



Me who wonders if the Sky will now Fall, or Hell Has Frozen Over....


What's this? A silly person who hides behind an idiot screen name?

If I wish to discuss fractal antennas, I will do so without hesitation and
great delight.
After all, the tide has long since rolled in...not that you've noticed:-)

You won't find any helpful info on BWA on this NG. It's not the right venue.

Go hide behind that rock again, Ol' fella!

73,
Chip N1IR

Here is an interesting example of wearable antenna. It is directional,
alas...

http://www.wearable.ethz.ch/bluetexantenna.0.html

Here's how to modify this concept to make it "quasi-omnidirectional":

Make a dipole feed on the apex of the shoulder, drop one radiator down the
shoulder in front of, another - behind the body. Stitch it inside the suit.
For radiator, use one inch strips of material similar to one on the website
above, or any sort of fine conductive mesh. Match by adjusting lengths of
the radiators not to expected resonant length but to low SWR at your
required frequency. If the impedance will be too low - offset the feed
point.

Good luck.

Andrey

PS: say hi to Mr. Fractenna - he is playing his usual stunt, funny to watch.



"icelord" wrote in message
om...
Greetings,

I'm currently developing a project which requires a specialized
antenna. The system consists in a sensor equipped suit that delivers
the data to a server. I'm having problems findind a suitable antenna
for the suit, since it requires to be integrated on the suit or in a
backpack (whip antennas are out of the question, since the suit can't
have any holes). The main problem is the human body effect and the
size constraints. Gain is also a major requirement since the range of
the operations will be 400 meters with line of sight.
(Server side: 10 dBm Tx Power and a 6 dB whip antenna, Suit side: -96
dBm sensibility- freq:433 MHz)

I've tried a patch antenna (similar to the one provided by linx
technologies) but it didn't perform well. I've also tried a small whip
antenna but the ground plane dimensions aren't suitable for
integrating this type of antennas in the backpack. I've also found a
dipole body worn antenna ( http://www.panorama.co.uk )., but I'm not
sure of its performance. Currently I'm trying to develop my own
antenna, which consists of a pcb small loop antenna. I'm asking for
sugestions and maybe antenna references for this type of application.

Thanks in advance.

Wonderful example of 20th century state of the art antennas.

Go with it Andrey!

Check the calendar BTW.

Say, where is that PLUG for your antenna services?

73,
Chip N1IR

icelord wrote:
Gain is also a major requirement...

Gain implies directionality. You probably want low gain, unless you can
maintain a constant aim from The Suit. Think about it.

400 meters with line of sight.
+10 dBm Tx Power and a 6 dB whip antenna
Suit side: -96dBm sensibility [spelling!]
freq: 433 MHz

Ask the current US president about radio receivers hidden under
ill-fitting suits. I believe that he has some recent hands-on
experience with the subject...

This seems to be a trivial problem. Any old 6-inch wire should work. If
not, why not use a higher gain antenna at the "server" end of the link?
Also - police "wires" (mics) work, you shouldn't have any problems.