IS12: Transmission Equations for Single and Multiple Antenna Systems – from Basic Formulations to Antenna Measurements in Complex Environments
Thursday 3:40 - 4:20pm - Room Bordeaux
Thomas Eibert
Technical University of Munich, Munich, Germany
Abstract
Under far-field conditions, the transmission of electromagnetic waves is commonly described by the Friis transmission equation, which is just derived from energy conservation. Wave propagation effects can be included by ray concepts together with appropriate phase terms. The corresponding transmit and receive antenna transfer functions indicate that the transmission and reception behaviors of electromagnetic waves are different in the time domain due to different frequency dependencies and some people even say that single antennas are, therefore, not reciprocal in the time domain. Motivated in particular by the needs of near-field antenna measurements, we will look into a couple of near-field antenna transmission equations, where we will find that spectral formulations of such transmission equations are commonly advantageous in terms of physical insight and numerical treatment and we will show that single antenna transmission equations are known, which would not raise any question on the time domain reciprocity behavior of antennas. A very flexible and numerically advantageous near-field transmission equation works with spectral propagating plane wave representations and it is found that this equation is nothing else than a near-field generalization of the Friis transmission equation. Based on this transmission equation, we will formulate antenna field transformation algorithms and we will show the performance of such algorithms for field transformations in complex environments, where reflection and scattering effects are involved or where only near-field measurements without phase information are available.