I fear your latest posts are further confusing your intentions.
In terms of RF engineering, an antenna is a device with non-zero coupling to far-field. Inductive couplers are designed to receive or generate a magnetic near-field. They are used in a kHz to multiple 10 MHz range to transmit data or power wirelessly. They can be described as AC magnetical devices, you don't need the capabilities of a full featured EM solver like CST (but you can use it nevertheless).
The 50 Hz power that can be harvested in a home enviroment will be hardly above a µW level, I fear the project is doomed to failure. You may be able to receive higher mW levels under an overhead power cable.
Microstrip patch antennas have dimensions comparable to wavelength, a realistic application range starts at several 100 MHz.