Coupling and impedance matching in Aperture coupled antennas

Can any one help me to explain the realationship between coupling and impedance matching in Aperture coupled microstrip antennas? And how to optimize each one?

Regards,
Hassan

Hi Hassan,

This book Robert A. Sainati, "CAD of Microstrip Antennas for Wireless Applications"
presents some guidelines to this design. Also, the Microstrip antenna handbook, from Bhartia et al probably contains some other pieces of information regarding this design.

From what I remember designing this kind of patch antenna, you may use a lambda over two slot, which gives the best efficiency and bandwidth, but the back side radiation is too strong. Alternatively, you may employ a smaller slot, and the coupling may be increased by the use of "dog bone" pattern, as a paper from Prof. Pozar describes. The impedance matching is done by means of a piece of line that extends beyond the slot - a stub.

I hope it helps you,

brazilian

Thank you brazilian,
what i'm not sure about excatly is how to judge the that design has better coupling or impedance matching by looking at the S11 graph and Smith Chart?

regards,
Hassan

You should assign a port to the feed microstrip/stripline, and by seeing the S11 ou get a indication of the matching. S11 around -30dB is enough, when simulating.

and also check the gain of the antenna, on the far field post processing unit of your simulator. With this value you see if your antenna is radiating well or if its just a lossy cavity.

too many items to make a compromise in between: good coupling, good impedance matching and the low back radiation and higher gain. i will do many sims and compare.

Thanks

Hassan