anechoic chamber new england
The complete design of an anechoic chamber is non trivial task. You should consider many aspects, not only electromagnetic. For instance, you need a perfectly horizontal floor: no inclination is ment to be present on the floor.
Anyway, the main points I would consider in the design are the dimensions of the chamber, that practically limit the FarField range, and the choice of the absorbing panel, that practically limit the NearField range.
One should also consider the scanning system: the scanning area impacts on the truncation error in NF measurements and therefore it limits the max angle of the radaition pattern in NF-FF trasformation (max u-v component in the visible region). Hence, Once chosen the band of interest, I would consider the worst case and I would estimate approximately the minimum area of scanning.
Many other aspects concerning the shielding, the slides, the connectors, the cables, the rotatory joints one should consider. But, I would consider them in a second phase of the designing, once.