Arbitrary units or unitless plot to protect data?
If that paper is submitted to IEEE Transactions on Microwave Theory and Techniques (and judging by comments, this journal should be a decent enough fit for the purpose of this discussion), you would have to provide the measurement results. The journal guidelines explicitly ask for it and no arbitrary units or unitless plots will suffice.

Reproducibilty of the research is very important. And obfuscating the data certainly goes against it. If this plot &amp; experiment itself is crucial for the paper – and you are not allowed by any means to disclose the parameters required to reproduce your experiment – you don't have a paper. Which might be sad, but that's not "the science" and "scientific process" fault, but ITAR (if that's the case) and yours, by (un)willingly accepting their terms.

One might judge that this is a conference paper, not a full journal one. But I, personally, prefer to have very similar standards for both conference &amp; journal papers – and a lot of conferences have a similar (if not better) review process.