**2.1 Hardware**

The heart of the system concept is the monopole antenna array submerged in a lossy glycerin: water coupling bath. As discussed in the Introduction, the monopole antennas offer important advantages such as small size, ease of modeling and broad bandwidth while also presenting different opportunities. The major trade-off is that the signal attenuation is great, even for a typical physical distance of 15 cm across the lossy medium in the illumination chamber, such that most commercial vector network analyzers are inadequate. This has changed somewhat in that there are now commercial 24 channel systems from Rohde & Schwartz (Munich, Germany) and Keysight Technologies (Santa Clara, CA); however, their costs can easily exceed \$100 K depending on the options necessary. For realizing an actual system, the most critical trade-offs are cost versus performance. In our case, this discussion involved numerical modeling concerns along with critical aspects of the microwave technology. For
