Location of probe for CP patch antenna with truncated corners

[dansmith890]

I'm designing a circularly polarized patch antenna for a university project. The antenna is to be fed with a coaxial cable with an SMA connector.
My method has been to use a square patch with truncated corners. I have found equations for the length and width but I cannot find any equations or resources to calculate the location of the connection probe on the patch. Neither Antenna Theory by Balanis or other IEEE reports on similar projects seem to detail how the feed location is determined.

 

[rizwan183]

The feed point must be located at that point on the patch, where the input impedance is 50 ohms for the resonant frequency. Also first find the location where return loss is negative.To find optimal location use trial and error method to determine the co-ordinates of feed point. In HFSS you can use parametric analysis to find your solution.

Rizwan,

 

[streamlet]

There are discussions in C.A. Balanis' classic antenna book, as I can remember. As a rule of thumb, try different feed locations along the middle line of the patch. A feed location at the patch edge leads to the maximum input impedance, while a feed location at the patch center brings about an equivalent short. Therefore the feed location for the desired 50-ohm lies at somewhere between.