[SOLVED] bandwidth of microstrip antenna circular

I am wanting to lower the bandwidth of microstrip antenna circular. What parameters can I change to reduce bandwidth.
Thanks.

You can reduce the frequency bandwidth by reducing the height above the ground plane. If you have other then air between the patch and the groundplane, smallest frequency bandwidth will be limited by the loss factor of the dielectric.

Further reduction in height will not reduce bandwidth and directivity, but will reduce the gain significantly. When the height becomes very small, copper loss will limit the frequency bandwidth.

If you change the height, you will have to redesign your matching also.

Thanks.
I'm working with circular microstrip antennas and I'm starting studies with HFSS. I wonder how can I know that ideal height I use for this operation frequency of 11.8GHz, antenna radius 2.5mm, 134um thickness and dielectric constant of 8.8-9.5?

Hello,

There is no ideal height. It depends on what material thickness you can get, loss factor of dielectric, maximum thickness allowed for the complete antenna, required frequency bandwidth, production tolerance, etc.

Generally spoken, reducing the height: reduces the useful frequency bandwidth, reduces the gain (because of increase of dielectric loss), does not change the directivity significantly, and increases the edge fed input impedance.

Changing height also changes the resonant frequency somewhat, because of the change in the fringing effect.

If total noise is of importance (reception case for example), you want good radiation efficiency (so gain is very close to directivity).

If you want to design a very narrow band antenna, you also have to consider temperature dependence of dielectric and thermal properties.

---------- Post added at 17:09 ---------- Previous post was at 17:02 ----------

Given your free space wavelength (25mm), dielectric thickness of 134um is very small (0.005lambda free space). Increasing the heigth will probably increase the gain and useful bandwidth.

Thanks again for your attention. But I'm using HFSS to simulate an experimental measure so I am working to make the simulation result is similar to the experimental measurement. So I'm trying to understand what I can modify the microstrip to increase / decrease the bandwidth, frequency and intensity. If you could give me a summary of what I change the antenna booster for these parameters (bandwidth, frequency and intensity) would help me quite.