Hi,
Near field is interesting. The drawback, as you probably know, is that the signal strength drops off fast with distance. If you want to calculate, you dont have to calculate the whole field really, just line of site to get an idea what is happening. I had posted some info on Biot Savart right here on ETO some time ago with a full explanation of the technique to calculate the field at a point in space at any distance. I didnt get a chance to post the techniques for a circular ring or ellipse yet, but i could probably just show the result, and maybe develop the equation for the helix too (coil of wire, with or without core). That would be interesting i think.
Are you having trouble deciding what transmit frequency to use?