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Dual slant linear polarization for WiMax patch antenna design

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Wi Max patch antenna

Hello,

If you start from a circular polarized patch (that used a divider with 90 degr phase shifter), you can make your patch. Do not start with a circular polarized patch that uses one feed only.

Make sure your patch width is same for X and Y directions (for example square, circle, etc). Some internet search will provide you examples. Each linear patch with same X and Y direction (eq. square, circle) you can use for dual polarization.


Conversion to dual polarized, +/-45 degr slant linear
Remove the divider and 90 degrees phase shifter. Now you have two inputs to the patch that provide orthogonal polarization. With that patch you can make polarization diversity (lin/vert, 45, -45 slant linear).

When you started from a linear patch, just add the second port 90 degrees rotated. Because of this, S12, S21 will be low.

Reducing the height of the patch above ground, reduces useful bandwidth and increases edge-fed impedance. If required you can make the impedance transformation with quarter wave sections. Of course you can also use two probe feeds.
 
Wi Max patch antenna

Hello,

When you do some web search, you will find many papers on patch antenna design.

Please find below an example that used EI3D. Note that this antenna is for linear polarization with one input (as the patches are rectangular instead of square).

One note on simulators that assume infinite dielectric: The radiation pattern calculation is not good at low elevation. It gives a null at zero elevation (theta = 90degr). In reality you will have radiation under zero elevation when you have a dielectric between ground and patch. If you have a newer version of IE3D you can simulate with finite dielectrics giving correct results, also under low elevation.
 
Re: Wi Max patch antenna

MODERATOR ACTION: You get a warning - by uploading IEEE papers

thanks for the material

I hav designed many patch antenna in different feed.. problem is basically to achieve +45 & -45 degree slanted linear polarization and both feed should be in 40 db isolation.
I am trying with this paper...

would this dual slant design is good one here...if i change the feed to coaxial.
 

Wi Max patch antenna

Hello,

As -45 and +45 degrees are 90 degrees out of phase, it is not that difficult to make, as this is also requried for a circular polarized patch. However 40 dB isolation over full bandwidth is not easy. Try to figure out whether this is really required.

The paper discusses basic patch design, you have to add your second feed yourself. to get -45/+45, you have to rotate the patch over 45 degrees so that both feeds are below or above the center of the patch.
 

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