The microwave imaging system used to collect the EIGOR data is fully described in . A photograph of the system and a close-up of the antenna as well as two schematics of the chamber are shown in the figures. The system consists of 24 double- layer vivaldi antennas (DLVAs), supported inside a Plexiglas imaging chamber. The antennas have an operating bandwidth from 3 to 10 GHz (stipulated as the continuous frequency range for which S11 is below -10 dB). A detailed description of the antennas can be found in [13,14]. Additional behavior of the antennas when co-resident in the chamber is available in .
The microwave transmitter/receiver consists of a two-port Agilent 8363B PNA-Series Vector Network Analyzer (VNA). The VNA is connected to the antennas
with a 2x24 cross-bar mechanical switch (Agilent 87050A-K24), which provides
isolation of greater than 95 dB over the frequency range of interest.
The exterior Plexiglas cylinder has an inner radius of 22.2 cm. Each Vivaldi antenna
is 7 cm long, and the base is held 3.0 cm from the wall by the connectors. Thus,
the tip of the antenna is located 10 cm from the edge of the wall, and the maximum
imaging domain, D, consists of a circle of radius 12.9 cm, located at the center of
the chamber. If a square domain is used, the maximum size is a length of approximately 18 cm.
In practice, we have used an imaging domain, D of 12 cm sides, and all targets t
inside the 12x12 cm imaging domain. During data collection, the chamber was surrounded by radar absorbing material (RAM).