| PhD Seminar

Name of the Speaker: Mr. Varatharajan M (EE21D062)
Guide: Dr. Bharath Bhikkaji
Venue: ESB-244 (Seminar Hall)
Online meeting link: https://meet.google.com/vbn-vnqc-oza
Date/Time: 9th April 2025 (Wednesday) , 3:00 PM
Title: Sparse Optimization approach to Localization of a Time-Harmonic Electromagnetic Point Source in a cavity with magnitude only measurements and Time Reversal

Abstract :

Electromagnetic Time Reversal (EMTR) refers to recording an electromagnetic signal transmitted by a source at the receiver and transmitting back a time-reversed version of the recorded signal from the receiver’s location. It was shown that such a reversed transmission would re-trace the path back to the source. This property can be used to localize the source. It finds applications in indoor positioning, biomedical engineering, geolocation of lightning, partial discharge localization in transformers, and fault detection in power systems.

Measuring electromagnetic transients at radio frequencies is difficult. Usually, magnitude and phase are measured at a band of frequencies. These frequency domain measurements are transformed to get the time domain data. The need for phase information limits the usage of EMTR for various applications. Further, EMTR fails for time-harmonic sources. This talk will focus on localizing a point source using magnitude-only measurements.

A time-harmonic point source that radiates an electromagnetic field at a specific frequency is considered. The source is assumed to be at an unknown position within the cavity. Scatterers of known geometry and dielectric constants in the cavity alter the source field. The magnitude of the electric field is measured at specific locations within the cavity. Using these magnitude-only measurements, the location of the source is determined. Linear constraints based on electromagnetic time reversal are derived. These constraints depend only on the magnitude of the electric fields. A convex optimization problem subject to the derived linear constraints is formulated. The solution to this optimization problem reveals the source location. Simulation results validating the proposed method are presented.