Caracterização banda larga de antenas impressas sobre substratos com pequenas perdas: uma abordagem via FDTD/WP-PML e expansão em multipolos esféricos no domínio do tempo

Abstract

In this work the characterization of wide-band printed antennas with lossy substrates is introduced by means of an approach based on time-domain computacional electromagnetics methods, namely, the finite-difference time-domain method with well-posed perfectly matched layers (FDTD/WP-PML) and a recently developed time-domain sphericalmultipole expansion. The application of the FDTD/WP-PML to printed antennas typical geometries allows the determination of their electrical properties as circuit elements: the return loss and input impedance. The equivalence principle is applied to the tangencial fields all over the FDTD/WP-PML spatial grid and the use of the spherical-multipole expansion leads to a near-to-far-field transformation, and energy and power norms of temporal signals are used to obtain the antenna radiation patterns for transient and steady-state responses. Time-domain computational electromagnetics methods have been chosen in this work because of the state of the art in printed antennas characterization intended to their application in modern digital multi-band communication systems, multiple-input multiple-output (MIMO) and ultrawide band systems (UWB). The main advantage of time domain multipole approach is that the radiated fields can be obtained for an antenna excited by any sources with pulsed temporal behavior and thus it allows the characterization of its radiation pattern in time and frequency domains. Such approach is very useful on performing an unified characterization of UWB antennas. Results are obtained for the return loss of MIMO multi-band and UWB antennas, as well as for the radiation pattern of an UWB antenna, and compared to those determined from standard methods available in the scientific literature in order to show the applicability of the methodology that has been developed herein.