Physical Principles of Antenna Systems

This book intends to bridge the gap between theoretical physics and the engineering of antenna systems. It therefore consists of two parts. The first part focuses on the physical principles of classical electrodynamics. Based on Maxwell's equations and the Lorentz force law, we derive, in all mathematical detail, waves in empty space, the great laws of conservation of charge, energy and momentum, the Einstein equivalence principle of mass and energy, the Lorentz transform and the transformation of the fields, the field invariants, the covariant description of electrodynamics using four-vector potentials, selected relativistic effects and the complete solution of the field equations. The second part explores the engineering applications of those principles for antenna systems. It includes in-depth coverage of radiation resistance, available power, effective area, the reciprocity theorem, currents in conductors, equivalent circuits, induced antenna current and voltage, directivity and super directivity of antenna arrays, antenna mutual coupling, multiport models for antenna systems, matching networks and near-field communication. The appendix provides a full treatment of the mathematics of vector calculus.