The subject of smart antennas is beginning to enjoy immense popularity due to the current exponential growth in all forms of wireless communications and sensing. This rapid growth has been facilitated by advancing digital signal processing hardware and also by the global interest in wideband wireless applications. Many in the wireless communication world are hoping to utilize smart antennas to boost capacities, expand bandwidths, increase signal-to-interference ratios, mitigate fading, and improve MIMO communications. Many others in the defense community are hoping to utilize smart antennas to help facilitate secure communications, direction finding, waveform diversity applications, MIMO radar, and multi-mission operations. Both groups are looking to use the benefits of smart antennas for similar reasons but are approaching the subject from different requirements and perspectives. This text has been written in the hopes of providing each group with a fundamental understanding of smart antennas without needing to tie the treatment to any one specific application.