Micro-Doppler frequency comb generation by rotating wire scatterers

Kozlov, Vitali; Filonov, Dmitry; Yankelevich, Y.; Ginzburg, Pavel

doi:10.1016/j.jqsrt.2016.12.029

Cited by 13 publications

(23 citation statements)

References 25 publications

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“…The investigated memory effect is universal and can emerge in many wave-related disciplines and scenarios, e.g., optical, where molecules and even macroscopic structures are being rotated with laser beams [40][41][42][43][44] and optofluidics, where timedependent Purcell enhancements can emerge, 45,46 in radar, LIDAR, and sonar, where the micro-Doppler signatures produced by rotating blades of a helicopter are of interest, 34,47,48 and, even in astronomy, where neutron stars can be approximated by rotating dipoles. 49 Although the effects of rotation on scattering were comprehensively studied in the past (e.g., Refs.…”

Section: Summary and Discussionmentioning

confidence: 99%

“…Indeed for infinite pulse length, the result converges into a discrete comb, which is separated in frequency by 2 _ θ (as in Ref. 34, which considers CW radiation). For short pulse lengths shown in Fig.…”

Section: Experimental Verification Of Quasistationarymentioning

confidence: 93%

“…It will be sufficient to say that in the rest frame of the dipole, the point of scattered field observation is also moving periodically with the rotational frequency, meaning that the scattered field will have frequency components of 2ω AE in the lab frame. 34 The mathematical derivation presented in this section is in fact more general and applies to more than rotating dipoles alone. When moving from Eqs.…”

Section: Induced Moments Of Rotating Dipoles Exact Versus Quasistatimentioning

confidence: 99%

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Memory effects in scattering from accelerating bodies

et al. 2020

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Interaction of electromagnetic, acoustic, and even gravitational waves with accelerating bodies forms a class of nonstationary time-variant processes. Scattered waves contain intrinsic signatures of motion, which manifest in a broad range of phenomena, including Sagnac interference, and both Doppler and micro-Doppler frequency shifts. Although general relativity is often required to account for motion, instantaneous rest frame approaches are frequently used to describe interactions with slowly accelerating objects. We investigate theoretically and experimentally an interaction regime that is neither relativistic nor adiabatic. The test model considers an accelerating scatterer with a long-lasting relaxation memory. The slow decay rates violate the instantaneous reaction assumption of quasistationarity, introducing non-Markovian contributions to the scattering process. Memory signatures in scattering from a rotating dipole are studied theoretically, showing symmetry breaking of micro-Doppler combs. A quasistationary numeric analysis of scattering in the short-memory limit is proposed and validated experimentally with an example of electromagnetic pulses interacting with a rotating wire.

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Section: Summary and Discussionmentioning

confidence: 99%

Section: Experimental Verification Of Quasistationarymentioning

confidence: 93%

Section: Induced Moments Of Rotating Dipoles Exact Versus Quasistatimentioning

confidence: 99%

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Memory effects in scattering from accelerating bodies

et al. 2020

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“…For real targets in field conditions the phase difference is unlikely to be perfectly linear, partially owing to the fact that the target may fluctuate, e.g. change direction rapidly, enter an area that degrades SNR conditions, or have different moving parts that add additional modulation to the reflected echoes, termed micro-Doppler [38][39][40] . The phases in the plots shown on Fig.…”

Section: Methodsmentioning

confidence: 99%

Broadband Radar Invisibility with Time-Dependent Metasurfaces

Kozlov

Vovchuk

Ginzburg

2021

Preprint

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Concealing objects from interrogation has been a primary objective since the integration of radars into surveillance systems. Metamaterial-based invisibility cloaking, which was considered a promising solution, did not yet succeed in delivering reliable performance against real radar systems, mainly due to its narrow operational bandwidth. Here we propose an approach, which addresses the issue from a signal-processing standpoint and, as a result, is capable of coping with the vast majority of unclassified radar systems by exploiting vulnerabilities in their design. In particular, we demonstrate complete concealment of a 0.25 square meter moving metal plate from an investigating radar system, operating in a broad frequency range approaching 20% bandwidth around the carrier of 1.5GHz. The key element of the radar countermeasure is a temporally modulated coating. This auxiliary structure is designed to dynamically and controllably adjust the reflected phase of the impinging radar signal, which acquires a user-defined Doppler shift. A special case of interest is imposing a frequency shift that compensates for the real Doppler signatures originating from the motion of the target. In this case the radar will consider the target static, even though it is moving. As a result, the reflected echo will be discarded by the clutter removal filter, which is an inherent part of any modern radar system that is designed to operate in real conditions. This signal-processing loophole allows rendering the target invisible to the radar even though it scatters electromagnetic radiation.

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“…In this case, it could be shown that the field scattered from this object, being rotated around it's center (position of the effective point dipole), will have only one additional harmonic at ( is the angular rotation frequency) and it does not depend on the position of the detector (e.g. [12], [8]). Objects with nontrivial internal structure could generate an entire frequency comb of micro-Doppler shifts with relative amplitudes, dependent on the detection direction.…”

Section: Theoretical Formulationmentioning

confidence: 99%

Asymmetric micro-Doppler frequency comb generation via magnetoelectric coupling

2017

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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.

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Micro-Doppler frequency comb generation by rotating wire scatterers

Cited by 13 publications

References 25 publications

Memory effects in scattering from accelerating bodies

Memory effects in scattering from accelerating bodies

Broadband Radar Invisibility with Time-Dependent Metasurfaces

Asymmetric micro-Doppler frequency comb generation via magnetoelectric coupling

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