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Resonance Frequency of the Antenna.

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anwersbh

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How can i determine the resonance frequency of the antenna has the figure below? Thanks.

1280.JPG
 

This is the smith chart.
 

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"Resonance" frequency (im(S11) = 0) is about 5 GHz, but radiation resistance is > Z0, not matched. In practice, the matching may be sufficient for the intended antenna purpose.,
 

How did you know that the radiation resistance is more than Zo? Thanks.
 

Radiation resistance is something special, what you discuss here is input resistance.
 

Radiation resistance is something special,
what you discuss here is input resistance.
If we can ignore copper loss, dielectric loss, matching element loss, guided loss, etc., real(Zin) is equal to radiation resistance.

Even if loss is not zero, real(Zin) is close to radiation resistance in many cases.
Here I treat object including matching elements as antenna, although I don’t think matching should be included in antenna.
 
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If we can ignore copper loss, dielectric loss, matching element loss, guided loss, etc., real(Zin) is equal to radiation resistance.

Yes, in an ideal world things are ideal, which makes it simple.

In my work on antenna simulation, I can separate radiation resistance from losses, and losses are often a major influence.
For patch antennas on FR4, we have large dielectric loss.
For electrically small antennas, as used in many devices today, we often have radiation efficiencies of 50% or less, so that radiation resistance is much smaller than input resistance.
 

For patch antennas on FR4, we have large dielectric loss.
Even if we use low loss substrate such as Teflon, loss due to surface wave is fairly large for patch antenna.

Surface wave does not contribute to radiantion but it causes mutual coupling of patch array antenna.
 


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