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Recent developments make it possible to radiate and coherently detect electromagnetic pulses consisting of a few half-cycles of a sine wave having a period on the order of 10 ps. The antennas involved are compact, typically consisting of conducting films on thin dielectric substrates having lateral dimensions of about 2 cm. Short, broadband pulse technology can be used for position sensing, object identification, and for monitoring the state of an object. Such target interrogation may have application to robotics. This possibility is explored here, and an example of the dependence of the scattered pulse on the internal state of an object is presented. The short electromagnetic pulses (SEP) permit position sensing of objects with spatial resolution on the order of 1 mm. They also permit identification of objects and the monitoring of their state. This follows because, depending on its size, shape, and the materials from which it is constructed, an object will exhibit a series of resonant frequencies at which it strongly reflects electromagnetic waves of harmonic time dependence. When illuminated by SEP, having frequency content spread over a wide bandwidth, these resonances will be excited. The resonances appear in the late-time tail of the scattered pulse. This late-time response is almost independent of the orientation of the object, and can therefore be used for identification. For targets that involve conducting bodies with aperture coupling to internal cavities the externally observed resonances can be especially useful in monitoring changes in the internal structure. The illustrative example demonstrating this aspect involves a slit- coupled closed shell with an internal load. If the shell and load are good conductors it is shown that the resulting high-Q resonances are highly sensitive to changes in the locatio of the load.
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