Asymmetric Micro-Doppler Frequency Comb Generation via Magneto-Electric Coupling

TL;DR

This paper investigates the generation of asymmetric micro-Doppler frequency combs from rotating, magneto-electric particles, revealing how their geometry and coupling influence the spectra, with experimental validation at 2GHz.

Contribution

It demonstrates the generation and analysis of asymmetric micro-Doppler combs from hybrid magneto-electric particles, highlighting the impact of structural asymmetry and coupling on the spectra.

Findings

Backward comb shows fundamental and odd harmonics

Forward comb peaks at doubled frequency and multiples

Particle dimensions and coupling strength affect comb features

Abstract

Electromagnetic scattering from moving bodies, being inherently time-dependent phenomenon, gives rise to a generation of new frequencies, which could characterize the motion. While a standard linear path leads to a constant Doppler shift, accelerating scatterers could generate a micro-Doppler frequency comb. Here, a spectra produced by rotating objects, was studied and observed in a bi-static lock in detection scheme. Internal geometry of a scatterer was shown to determine the spectra, while the degree of structural asymmetry was suggested to be identified via signatures in the micro-Doppler comb. In particular, hybrid magneto-electric particles, showing an ultimate degree of asymmetry in forward and backward scattering directions were investigated. It was shown that the comb in the backward direction has signatures at the fundamental rotation frequency and its odd harmonics, while in the forward scattered field has the prevailing peak at the doubled frequency and its multiples. Additional features in the comb were shown to be affected by the dimensions of the particle and strength of magneto-electric coupling. Experimental verification was performed with a printed circuit board antenna, based on a wire and a split ring, while the structure was illuminated with at 2GHz carrier frequency. Detailed analysis of micro-Doppler combs enables remote detection of asymmetric features of distant objects and could find use in a span of applications, including stellar radiometry and radio identification.