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Microstrip PCB antenna for 2.4 GHz WLAN



 
 
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  #1  
Old November 1st 04, 10:43 PM
Kasper Vibe Grevsen
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Default Microstrip PCB antenna for 2.4 GHz WLAN

Hello HAMmers

I want to build an internal WLAN antenna for my notebook computer to be
placed in the screen.
The available space is 163 x 12 mm. A quarter wavelength at 2442.5 MHz is
30.7 mm. I haven't been able to find much info about microstrip design so I
hope you might be able to give some suggestions as to a good design.

I have thought about 'stretching' a bi-quad to fit the dimensions, but then
the angles cannot be 90°. Would that be a problem? Can you suggest a better
design to try? This is my first antenna design so please bear with me if
these are beginner questions.


Thanks

--
Kasper


  #2  
Old November 2nd 04, 06:04 AM
Richard Clark
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Default

On Mon, 1 Nov 2004 23:43:18 +0100, "Kasper Vibe Grevsen"
wrote:

The available space is 163 x 12 mm. A quarter wavelength at 2442.5 MHz is
30.7 mm.


Hi Kasper,

I haven't been able to find much info about microstrip design so I
hope you might be able to give some suggestions as to a good design.


The standard half-wave dipole comes to mind as it so easily fits into
your available space.

I have thought about 'stretching' a bi-quad to fit the dimensions


Why introduce problems when a simple solution exists?

Or, as Einstein expressed it: "keep it simple, but not too simple."

73's
Richard Clark, KB7QHC
  #3  
Old November 2nd 04, 02:28 PM
Kasper Vibe Grevsen
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Default


"Richard Clark" skrev i en meddelelse
...
On Mon, 1 Nov 2004 23:43:18 +0100, "Kasper Vibe Grevsen"
wrote:

The available space is 163 x 12 mm. A quarter wavelength at 2442.5 MHz is
30.7 mm.


Hi Kasper,

The standard half-wave dipole comes to mind as it so easily fits into
your available space.


Hi Richard,

thanks for your suggestion,

that means a T-shape as I understand?
The horizontal part should be 2 x 30,7 mm, right?
How long should the vertical line be?
How wide should I make the tracks?
The cable is a 50 ohm coax.


--
med venlig hilsen
Unlock Århus - www.unlockaarhus.dk

Kasper Vibe Grevsen
Tlf 30 222 123


  #4  
Old November 2nd 04, 03:04 PM
Richard Clark
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Posts: n/a
Default

On Tue, 2 Nov 2004 15:28:39 +0100, "Kasper Vibe Grevsen"
wrote:
thanks for your suggestion,

that means a T-shape as I understand?
The horizontal part should be 2 x 30,7 mm, right?
How long should the vertical line be?
How wide should I make the tracks?
The cable is a 50 ohm coax.


Hi Klaus,

Although perfection requires precision and accuracy, your application
does not demand perfection. Besides, it is unlikely you are either
technically prepared to measure the properties of the antenna, nor buy
equipment that could do it simpler.

There are any number of factors that would impact the measurements you
describe above and one is simply building the antenna on a piece of PC
board (why not simply use wire?). Another point is that the dipole is
a "balanced" design, and your source of radiation is undoubtedly
"unbalanced." This, of course, probably means nothing to you, and
fortunately it has meant nothing to many who have ignored this
distinction too (which underlines that perfection is not required in
ordinary, day-to-day usage). Also, you don't include enough
information to offer an exact solution.

However, to answer your question by the parts:

Yes it is T shaped (see ASCII graphic below with fixed font);

Yes, the horizontal part should be about 2 x 30,7 mm;

The vertical lineS should be as long as they take to reach
the source
and
the ground;

The Horizontal tracks could be as wide as 1mm - if you make them wider
this reduces your need for precision if you wanted to be perfect;

If you are going to use 50 Ohm cable, you don't need vertical leads.

The pictorial equivalent (view with fixed font setting):

----------- -----------
| |
| |
| |
| |
| |

Returning to issues of perfection. If you encounter problems of
reception/transmission, they will be more due to the antenna
orientation and placement than they will be due to power level.

Back when we lived in caves, TV came through the air instead of
through a cable. We had rituals to adjust Rabbit Ear antennas (a
pagan WiMax shrine) until the picture got better. You are about to
embark in that same arcane practice - welcome to a brave new world.

73's
Richard Clark, KB7QHC
  #5  
Old November 2nd 04, 03:19 PM
Mark
Guest
 
Posts: n/a
Default

"Kasper Vibe Grevsen" wrote in
message ...
Hi Kasper,

The standard half-wave dipole comes to mind as it so easily fits into
your available space.


Hi Richard,

thanks for your suggestion,

that means a T-shape as I understand?
The horizontal part should be 2 x 30,7 mm, right?
How long should the vertical line be?
How wide should I make the tracks?
The cable is a 50 ohm coax.


It is a lot simpler than that...

A half wave dipole would be two tracks approx 30.7mm long as you say.
But.. you do not need a vertical line.
Coax can attach directly to the centre point.
Width of the tracks also depends on how much space you have.
The wider the tracks the bigger the bandwidth affected.

Also what may effect the whole installation is the polarisation of the
antenna,
horizontal or vertical.

This depends on the antenna on the other device. Same polarisation
recommended!



 




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