Deeply Subwavelength Localization with Reverberation-Coded Aperture

Abstract

Physics-compliant models of RIS-parametrized channels assign a load-terminated port to each RIS element. For conventional diagonal RIS (D-RIS), each auxiliary port is terminated by its own independent and individually tunable load (i.e., independent of the other auxiliary ports). For beyonddiagonal RIS (BD-RIS), the auxiliary ports are terminated by a tunable load circuit which couples the auxiliary ports to each other. Here, we point out that a physics-compliant model of the load circuit of a BD-RIS takes the same form as a physics-compliant model of a D-RIS-parametrized radio environment: a multi-port network with a subset of ports terminated by individually tunable loads (independent of each other). Consequently, we recognize that a BD-RIS-parametrized radio environment can be understood as a multi-port cascade network (i.e., the cascade of radio environment with load circuit) terminated by individually tunable loads (independent of each other). Hence, the BD-RIS problem can be mapped into the original D-RIS problem by replacing the radio environment with the cascade of radio environment and load circuit. The insight that BD-RIS can be physics-compliantly analyzed with the conventional D-RIS formalism implies that (i) the same optimization protocols as for D-RIS can be used for the BD-RIS case, and (ii) it is unclear if existing comparisons between BD-RIS and D-RIS are fair because for a fixed number of RIS elements, a BD-RIS has usually more tunable lumped elements.

Calibration-free speckle matrix imaging

“…The current approach of discarding it as random noise not only neglects the fact that “multiple-scattering noise”—despite its random appearance upon visual inspection—does contain profound mesoscopic correlations. More intriguing is the fact that multiply scattered waves may actually carry more information about the scene than “ballistic” waves: the sensitivity of waves to subwavelength scene details, and hence the waves’ ability to extract finely resolved scene information, increases with their dwell time 16 . Reverberation and multiple scattering can be thought of as generalizing the deeply subwavelength interferometric sensitivity from a conventional 1D interferometer to arbitrary geometries.…”

High-throughput volumetric adaptive optical imaging using compressed time-reversal matrix

“…However, multiple-scattered waves do also carry spatial information of the object. CTR-CLASS algorithm can potentially be extended to make the deterministic use of multiple-scattered waves in image reconstruction for further reducing measurement time or lowering the achievable spatial resolution well below the diffraction limit 34 .…”

Multipath Propagation of Acoustic Signal in a Swimming Pool—Source Localization Problem

“…The proposed algorithm is based on the geometrical model of the given pool; further research may explore an algorithm that does not depend on the cuboid-like pool shape. This may include an effort to apply machine learning techniques based on neural network training with live or simulated signals or measurements, as inspired by [ 12 , 13 ].…”

“…This algorithm relies on iterative removal of the echoes, starting from the most prominent one, and is numerically simpler than the joint estimation in the former algorithm. An interesting approach, employing the multipath propagation phenomenon for the improvement of the object location in a reverberant space, is described in [ 12 ]. A location accuracy down to 1/76 of the wavelength is reported.…”