Abstract: An electromagnetic interrogation system and methods for analyzing a target in a test bed are disclosed. A forced resonating antenna unit has a transmit element and a receive element both mounted on a platform movable over the test bed. An interrogation signal source generates a continuous stepped-frequency radio frequency (RF) signal. A plurality of receiver channels are connected to the receive element, and ratios of the scattered continuous stepped-frequency RF signal on a first one of the receiver channels and on a second one of the receiver channels each relative to a reference one of the receiver channels is derived as a measurement for each frequency step. A triggering module linked to the receiver channels generates a positional data value corresponding to a set of measurements for one or more stepped frequency sweeps. An analysis module generates test bed analysis results based upon multiple sets of measurements over time and the corresponding positional data values.