I came across this file when trying to explore my own ways of processing planar near-field data that I had already measured for my senior project. When exploring the topic of near-field to far-field transformation, I found various methods on how to complete the task of producing a far-field pattern from near-field measurements, such as multiple unclear ways on how to produce an angular map of the transformed data.
This is when I stumbled upon this file. NF2FF is a great and clear resource for understanding the near-field to far-field transformation process. The program goes above and beyond characterizing the far-field pattern, as it actually takes the user through a step-by-step processing of data and plotting from start to finish.
I would have to say it does require you to have extensive knowledge on the actual background of what you need to do, or you won't have a clue as to why certain things are being done (which isn't a bad thing). Also, the only aspect that may be somewhat confusing is the input process, but if you've come this far you probably already have an idea of what your own parameters are and how to work with them.
What I truly found amazing was the willingness of the author, Koen Van Caekenberghe, to provide assistance and advice. From my own experience, I had major trouble with taking the far-field spectral domain and applying an angular mapping technique to compare with my anechoic chamber data. Once Koen helped me, I found that his program is extremely accurate with planar near-field data processing up to around +-40 degrees. With probe compensation, this could be vastly improved out to +-75 degrees.