1 Antennas and Antenna Arrays

Antennas have become ubiquitous devices and occupy a salient position in wireless systems. Radio and TV as well as satellite and new generation mobile communications have experienced the largest growth among industry systems. The global wireless market continues to grow at breakneck speed and the strongest economic and social impact nowadays comes from cellular telephony, personal communications and satellite navigation systems. All of the above systems have served as motivation for engineers to incorporate elegant antennas into handy and portable systems. Many textbooks provide in-depth resources on antennas. Especially on antenna arrays, there are digests, studies and books containing extensive data and techniques. In the references given herewith [1–26], there are some of the best-known and most highly recommended books. A device able to receive or transmit electromagnetic energy is called an ‘antenna’. As seen in [6], the antenna plays the role of a transitional structure between free space and a guiding device. An antenna consists of one or more elements. A single-element antenna is usually not enough to achieve technical needs. That happens because its performance is limited. A set of discrete elements, which constitute an antenna array, offers the solution to the transmission and/or reception of electromagnetic energy. The geometry and the type of elements characterize an antenna array. For simplicity, implementation and fabrication reasons, the elements are chosen in such a way so as to be identical and parallel. For the same reasons, uniformly spaced linear arrays are mostly encountered in practice. In the following paragraphs, the properties of various antenna arrays will be presented.