Effect of Ground on the resonance of patch antenna

[snkhan]

Hello

I have simulated a simple square patch antenna. Parametric sleep of ground size shows lowering of resonance frequency.

What is the reason for the phenomena

Thanks

 

[nhomuathu_hanoi]

Most of present theories assume that the proposed microstrip antenna has a infinite ground plane then It will resonate at the length of λ/4. That's the reason why resizing ground plane size at a certain value causes the change of resonated frequency, I think.

 

[shahid78]

hi snkhan

one reason may be the change in the effective length of the patch antenna as you paramatrically change the size of the ground plane

can you tell whether the resonant frequency increases or decreases with the increase in the lenght of the ground plane size?


regards

 

[snkhan]

The resonant frequency decreases with the increase in ground size

 

[shahid78]

well based on this i can conclude that as you increase the ground plane size the effective length increases and thus resonant frequency decreases

i hope this clarifies your question

 

[byteptr]

"The resonant frequency decreases with the increase in ground size
"
Yes, it's just the same effect that I had measure on laboratory, but with a λ/4 2.4GHz vertical antenna.
In this case, the GND plane acts as known current mirror, I think that truncate the plate involves stationary waves into the plane, a no perfect mirror and this affects to antenna.

 

[madengr]

The resonant frequency decreases with the increase in ground size

You can also think of the ground plane providing more capacitance with increasing size, thus lowering resonant frequency according to f=1/(2*PI*sqrt(LC)).

 

[byteptr]

Yes.
I prefer think in distributed elements (if is possible) or in terms of waves for these cases since the distributed elements have a near-periodic reponse with frequency.

However It's true that 'capacitance increase' can be take as a qualitative example, and may be good approach in some cases