Determining angle of arrival of radio frequency fields using subwavelength, amplitude-only measurements of standing waves in a Rydberg atom sensor

TL;DR

This paper introduces a novel Rydberg atom sensor capable of determining the angle of arrival of RF signals using subwavelength, amplitude-only measurements of standing waves, eliminating the need for a phase reference.

Contribution

The authors develop a new Rydberg sensor that measures AoA independently of RF field strength and phase reference by imaging standing waves with a metallic plate inside the cell.

Findings

Achieved 1.7° angular resolution at 4.2-5.7 GHz

Demonstrated AoA measurement without a phase reference

Validated performance with robotic antenna positioning

Abstract

Deep subwavelength RF imaging with atomic Rydberg sensors has overcome fundamental limitations of traditional antennas and enabled ultra-wideband detection of omni-directional time varying fields all in a compact form factor. However, in most applications, Rydberg sensors require the use of a secondary strong RF reference field to serve as a phase reference. Here, we demonstrate a new type of Rydberg sensor for angle-of-arrival (AoA) sensing which utilizes subwavelength imaging of standing wave fields. By placing a metallic plate within the Rydberg cell, we can determine the AoA independent of the strength of incoming RF field and without requiring a secondary strong RF phase reference field. We perform precision AoA measurements with a robotic antenna positioning system for 4.2, 5.0, and 5.7 GHz signals and demonstrate a 1.7 deg polar angular resolution from 0 deg to 60 deg AoA and 4.1 deg over all possible angles.