"Iridescent" Reflective Tags to Enable Radar-based Orientation Estimation

TL;DR

This paper introduces passive iridescent reflective tags for radar systems, enabling accurate object orientation estimation with low complexity and analyzing factors affecting performance through simulations.

Contribution

It proposes a novel tag design based on leaky-wave antennas and develops a framework for orientation estimation using multi-tone radar, demonstrating near-optimal accuracy with low complexity.

Findings

Low impact of imperfect tag location on accuracy

Estimator performance depends mainly on system bandwidth

Optimal number of tones increases with sensing time under power constraints

Abstract

Accurate orientation estimation of objects can aid in scene understanding in many applications. In this paper, we consider use cases where passive tags could be deployed to assist radar systems in estimating object orientation. Towards that end, we propose the concept of passive iridescent reflective tags that selectively reflect different wavelengths in different directions. We propose a conceptual tag design based on leaky-wave antennas. We develop a framework for signal modeling and orientation estimation with a multi-tone radar. We analyze the impact of imperfect tag location information, revealing that it minimally impacts orientation estimation accuracy. To reduce estimator complexity, we propose a radiation pointing angle-based estimator with near-optimal performance. We derive its feasible orientation estimation region and show that it depends mainly on the system bandwidth. Monte Carlo simulations validate our analytical results while evincing that the low-complexity estimator achieves near-optimal accuracy and that its feasible orientation estimation region closely matches that of the other estimators. Finally, we show that the optimal number of tones increases with the sensing time under a power budget constraint, multipath effects may be negligible, signal-to-noise ratio gains rise with the number of tones, and many radar antennas can hurt estimation performance when the signal contains very few tones.