Retrodirective Dielectric Resonator Tag With Polarization Twist Signature for Clutter Suppression in Self-Localization System

Abstract

In a recently proposed indoor self-localization system, we excite dielectric resonators (DRs) in linear polarization (LP) as retrodirective passive tags, either as single DR, small array of DRs, or in combination with a spherical dielectric lens. DR tags mounted close to a reflecting wall suffer from large clutter return, which can supercede the DR tag signatures. To separate both into orthogonal polarizations, we design a polarization twist tag with two DRs tilted by ±45° and spaced by <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda $ </tex-math></inline-formula> /4. In the EM simulation and experiment, we show that this tag design allows efficient retrodirective scattering in cross polarization. The realized cross-polarization radar cross section (RCS) is equal to the scattering of a single DR in LP and 6 dB better than the RCS from a polarization splitting single DR with 45° tilt. This polarization signature is shown to allow separation of the DR signature from the high scattering level of a flat plate reflector placed behind the polarization twist DR tag. The potential of improving lens-DR combinations by using the polarization twist DR tag with circular polarization is also discussed.