Conventional and emerging waveforms for detection and imaging of targets behind walls

To date, waveforms used for through-the-wall detection and imaging range from classical (such as short pulse or impulse, and linear or stepped frequency modulated [FM]) to sophisticated (such as noise or noise-like, and M-sequence phase coded). Each of these waveforms has its own advantages 158and limitations. Most of these waveforms are traditionally designed for range resolution, Doppler resolution, and ambiguity considerations. However, in addition to considerations for scene resolutions, the choice of a suitable waveform for through-the-wall applications depends on a variety of other important factors, such as the environment (wall type and thickness, building layout, clutter type, and electromagnetic interference), operational requirements (need for tracking and/or imaging, human activity recognition, need for covertness, and size and weight constraints), and applicable frequency restrictions. Emerging waveform design techniques, such as target signature exploitation and chaotic waveforms, address these constraints and challenges associated with propagation through walls.