The basic function of radar is to obtain information about the object being tracked (radar target) by measuring the characteristics of the electro magnetic field scattered by the target. Originally, radar was used to measure the coordinate parameters defining the target location and movement. With improvements in hardware and software, and the introduction of new design principles, radar precision and resolving power became high enough to obtain the noncoordinate data necessary for target classification and for the measurement of the target size, shape, orientation and state, allowing target recognition and imaging. It is well known that the precision and resolving power of radar measurements are directly related to the parameters of the signals used. The desire to broaden the scope of information to be extracted made radar engineers turn to signals with a wide frequency bandwidth. These provide a space resolution of the order of a fraction of the target size and permit measure ment of responses from local scattering centres. Wideband radar measurements became possible due to the application of fast response equipment, which could generate radar pulses of nano and picosecond duration. The new radar tracking standards necessitated the use of radar characteristics which could adequately describe the properties of wideband signals and responses, permitting their classification in terms of informative features.

Ultra-wideband (UWB) signal analysis and synthesis requires a clear under standing of the changes which radar signals undergo during the processes of transmission, reflection and reception. In this respect, the relationship between UWB radar science and transient electrodynamics is more intimate than that between classical radar and electrodynamics. An important trend today is the development of mathematical target models capable of providing an adequate analysis of UWB signals reflected from a target of complex geometry. The progress in this field has been primarily due to the use of concepts and methods of the general dynamic systems theory and to the physical interpretation of the models in terms of solutions to inverse transient electrodynamic problems.

This chapter discusses UWB signal processing. UWB signal processing by radar meters can be subdivided into the preliminary, primary and secondary stages. Preliminary processing is aimed at signal extraction by rejecting various perturbations arising during the measurement. At this stage, however, only initial information necessary for solving inverse problems. This stage is followed by the primary processing of individual signals measured at a fixed position of the object with respect to the measuring antenna (probe). Its aim is to correct the dynamic characteristics of the meter's transmit-receive channel. Secondary processing represents a simultaneous processing of the whole array of signal measurements made at various positions of the object and the antenna (probe).