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Length of a Printed Dipole

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mprathap

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Hi All,

I have read in a couple of places that the length required for resonance for a given frequency for a dipole decreases when printed on a grounded dielectric substrate similar to a patch antenna. But I have never seen this happen in simulations and the length required remains closer to half wavelength.

Am I doing something wrong or what I see is correct? From my EM knowledge I do not expect this to happen since, a dipole printed on a grounded substrate still does not operate as a microstrip.

Some insight on this issue will be greatly appreciated.

P.
 

I think Printed dipole antennas dont have ground plane other wise it will be like patch antenna.
Also Length will be small compair to actual lambada by 2 for small frequencies.
I dont know about frequencies in range of 100 GHz.
 
The electrical length of an antenna depends on the effective relative permittivity. If it is suspended in air, the mechanical length will be the same as the electrical length. When the antenna is close to a material with Er>1, then the electrical length will be longer than the mechanical length (by a factor 1/sqrt(Er)), which needs to be corrected by physically reducing the mechanical length.
 

In addition to nschutten, the width of the planar dipole also makes quite a difference to the physical length. Usually, you would not want it to be very very thin.
 

Hi nschutten ,

I agree with you.

I have designed such dipole many times for different project , i have fabricated and measured the S11 and it was agree with the simulation.

The point is the lngth it still close to lambda/2 , i think this is cos its not patch antenna , and in case of using thin dielectric substrate layer below it , it acts like a free space cos its very thin.
 
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