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The millimeter wave (MMW) band of frequencies extends from 30 GHz to 300 GHz, with some fuzziness on both ends of this spectrum. The terahertz (THz) band extends from about 200 GHz to about 30 THz, despite the fact that the lower frequencies in this range are not strictly 1012 Hz or higher. These bands are also variously called submillimeter, far-infrared, and near-millimeter. In recent years, there has been some degree of hype associated with the capabilities of systems operating in these bands. Sometimes exorbitant claims have been made relative to the ability of these systems to see through walls, detect buried structures, and detect cancer cells, for example. In this chapter we shall examine some of these clams and assess their validity. We shall find that MMW and THz systems can do some amazing things, some of them not related to the above claims, and that there is substantial promise of even more interesting results. In this chapter we begin by discussing these atmospheric limitations, since they permeate the whole technology of MMW, sub-MMW, and THz technology. We then discuss MMW and THz sources, detectors, optics, and systems in separate sections. Finally, we present some results obtained using sensors operating in these bands. Perhaps the most interesting of these results demonstrate the capability to image objects at resolutions as good as λ/100, where λ is wavelength. These measurements show the connection between this sensor technology and applications to security.

In this chapter we describe some of the ideas being pursued in sensor scheduling as they apply to radar. A modern phased-array pulse- Doppler radar has several different parameters available for scheduling: waveform, beam-shape, beam direction, pulse repetition interval, etc. Choice of different values for these parameters provides different transmit modes for the radar and these modes in turn provide a variety of “blurrings” of the image of the scene. The application of ideas in scheduling to the different possible modes of the transmit phase of such a radar, has been shown in simulation to improve many aspects of the performance in tracking and detection of targets. We give a quick introduction to the ideas of radar followed by a discussion of some of the theoretical ideas involved, and with results of some simulations. We end with a discussion of the theoretical problem of scheduling the measurements and tracking of a one-dimensional system.

The first RADAR patent was applied for by Christian Huelsmeyer on April 30, 1904 at the patent office in Berlin, Germany. He was motivated by a ship accident on the river Weser and called his experimental system “Telemobiloscope”. In this chapter some important and modern topics in radar system design and radar signal processing will be discussed. Waveform design is one innovative topic where new results are available for special applications like automotive radar. Detection theory is a fundamental radar topic which will be discussed in this chapter for new range CFAR schemes which are essential for all radar systems. Target recognition has for many years been the dream of all radar engineers. New results for target classification will be discussed for some automotive radar sensors.

In order to improve upon automated sensor performance for security applications in public and private settings, numerous alternative sensor designs have been developed to provide affordable and effective detection and identification performance. Radio frequency (RF) sensors offer a balanced approach to system design for a wide variety of geometries and threat targets. These threat targets include persons carrying weapons and explosives, portable containers with contraband including cargo boxes, suitcases, and briefcases and fixed structures including building or underground facilities harboring criminals, terrorist or enemy combatants. In order to achieve the resolution required for the detection and identification of threat targets, separation of interference from the target response is essential. High bandwidth offers a conventional approach to high resolution sensing of the threat. An alternative approach, one based upon wide angular bandwidth (spatial diversity), is presented here.

The first demonstration that near infrared (NIR) light can be used to monitor the state of cortical tissues noninvasively through the skull was presented by Jobsis in 1977 [53]. About a decade later, researchers started looking at the potential use of NIR spectroscopy for functional brain activity monitoring. Early studies began with simple motor and sensory tasks demonstrating the feasibility of the technology for noninvasively assessing the state of cerebral activity in a localized area. More recent studies have attempted to monitor more complex cognitive tasks such as warfare management [48] and aircraft landing simulations [102]. In this chapter, the research surrounding the application of NIR imaging and spectroscopy to noninvasive monitoring of functional brain activity is reviewed. A comprehensive review of equipment technologies, mathematical models, and past studies is given with some emphasis on the technology’s potential in security and defense applications.