I have a question about phased array antenna

This paragraph is from “phased array antenna” by R.C.Hansen pp 273 , 274
Does anyone know what is the mining of “aperture” in this paragraph ?

“First, the scan element pattern (SEP) is computed for the corresponding infinite array. This SEP is then Fourier transformed [usually by discrete Fourier transform (DFT)] back to the “aperture”. Third, a periodic structure consisting of equally spaced finite arrays, with each array having the desired amplitude distribution and scan phase, is transformed. Fourth, these two transforms are convolved. Next the result is inverse transformed to get the SEPs over the periodic structure. Last, the SEP for one finite array is extracted, and multiplied by the isolated element pattern, yielding the final finite array scan element pattern.”
Thanks and regards.

Sounds like he is using an iDFT to get an equivalent current distribution back at an single element that could generate such a pattern. Since it is an infinite array there is no single element, so he just calls it an aperture, probably of equivalent area to get the same gain. Since he is convolving two current distributions that's the same as multiplying the patterns. I'm not sure what it's all about but it makes sense.

Dear madengr
Thank for your help
have you any example about that paragraph or some more information ?
I would like help you in other fields if you need.
I can't speak English very well please excuse me!