Smart antenna systems are those that can change their radiation patterns, gain, beamwidth, polarization, and other parameters 'on the fly' in response to the requirements of the communications channel/path, while an adaptive array switches antenna elements in and out to vary the performance of the antenna. Both smart antennas and adaptive arrays allow the coverage area of a telecommunications system to be automatically 'adjusted' (for example, coverage area is reduced when units are close to the base station or in a narrow segment of the total coverage area) for more efficient use of frequency space and transmitter power. This allows more users to share the same frequency range without interference to each other and improves the efficiency of the system or network. The increased crowding of the RF/wireless spectrum is rapidly making a solid working knowledge of smart antennas and adaptive arrays - like the knowledge conveyed by this book - mandatory for communications engineers. This book covers smart antennas for both narrowband and wideband communications systems. It discusses direction-finding/locating applications of adaptive arrays. It offers complete coverage of multiple-antenna and multiple-array systems.