Non-Hermitian broadside coupled split ring resonators with directional sensitivity

Abstract

Abstract Directional radiofrequency (RF) sensing, also known as radio direction finding, is essential in various applications that involve localizing RF sources. However, existing RF sensing technologies face challenges due to their large antenna sizes and complex RF signal processing circuits, which hinder the realization of miniaturized subwavelength direction sensors. In this article, we presented a non-Hermitian broadside coupled split ring resonators (BC-SRRs), which can identify the direction of an incident RF signal with angles ranging from 0° to 180°. The non-Hermitian Hamiltonian of the system, which can be interpreted by the temporal coupled mode theory, gives rise to asymmetric resonant modes of the BC-SRRs. The asymmetry allows the direct measurement of RF wave incident angle by probing the resonant strength of the two SRRs. For the proof of concept, we employed a one-stage Dickson voltage multiplier to rectify the RF signals and demonstrated angle sensing ability by relating the rectified voltage to the incident angle. Our results showcase the potential of the proposed technique using non-Hermitian BC-SRRs as a pathway towards subwavelength antenna-based radio direction finding.