Antenna design
The important parameters in antenna design are:
Efficiency
The losses in an antenna can be modeled as a series resistance with the radiation resistance. The sources of losses are:
Resistive losses
Resonance - energy can be trapped in a parasitic LC tank circuit and dissipate through resistances.
Substrate losses - if the thickness of the substrate is comparable to the $\frac{\lambda}{2}$, or half of the wavelength, some of the signal can travel through the substrate.
Design and simulation
The ANSYS HFSS suite can be used to design and simulate antennas.