Technically spoken, the antenna is nothing else but the transition between transmission channels. Typically this would be from coaxial to free air. This transition of course also has it's characteristics and delay profile. I think you could model this using 3D modeling software.
Antennas have a significant effect on how far one can send a signal. I would recommend looking up the meaning of gain, beamwidth, field of view, bandwidth as a start.
Basically the bigger an antenna the stronger the received signal and the more narrow the field of view.