Theory of electroporation: A review

When, in addition to the constant Doppler frequency shift induced by the bulk motion of a radar target, the target or any structure on the target undergoes micro-motion dynamics, such as mechanical vibrations or rotations, the micro-motion dynamics induce Doppler modulations on the returned signal, referred to as the micro-Doppler effect. We introduce the micro-Doppler phenomenon in radar, develop a model of Doppler modulations, derive formulas of micro-Doppler induced by targets with vibration, rotation, tumbling and coning motions, and verify them by simulation studies, analyze time-varying micro-Doppler features using high-resolution time-frequency transforms, and demonstrate the micro-Doppler effect observed in real radar data.

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Micro-Doppler effect in radar: phenomenon, model, and simulation study

Starting from Tesla's principles of wireless power transfer a century ago, this critical review outlines recent magneto-inductive research activities on wireless power transfer with the transmission distance greater than the transmitter coil dimension. It summarizes the operating principles of a range of wireless power research into 1) the maximum power transfer and 2) the maximum energy efficiency principles. The differences and the implications of these two approaches are explained in terms of their energy efficiency and transmission distance capabilities. The differences between the system energy efficiency and the transmission efficiency are also highlighted. The review covers the two-coil systems, the four-coil systems, the systems with relay resonators and the wireless domino-resonator systems. Related issues including human exposure issues and reduction of winding resistance are also addressed. The review suggests that the use of the maximum energy efficiency principle in the two-coil systems is suitable for short-range rather than mid-range applications, the use of the maximum power transfer principle in the four-coil systems is good for maximizing the transmission distance, but is under a restricted system energy efficiency (<;50%); the use of the maximum energy efficiency principle in relay or domino systems may offer a good compromise for good system energy efficiency and transmission distance on the condition that relay resonators can be placed between the power source and the load.

A Critical Review of Recent Progress in Mid-Range Wireless Power Transfer

This paper presents WiSee, a novel gesture recognition system that leverages wireless signals (e.g., Wi-Fi) to enable whole-home sensing and recognition of human gestures. Since wireless signals do not require line-of-sight and can traverse through walls, WiSee can enable whole-home gesture recognition using few wireless sources. Further, it achieves this goal without requiring instrumentation of the human body with sensing devices. We implement a proof-of-concept prototype of WiSee using USRP-N210s and evaluate it in both an office environment and a two- bedroom apartment. Our results show that WiSee can identify and classify a set of nine gestures with an average accuracy of 94%.

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Whole-home gesture recognition using wireless signals

Multiple-input-multiple-output (MIMO) wireless systems use multiple antenna elements at transmit and receive to offer improved capacity over single antenna topologies in multipath channels In such systems, the antenna properties as well as the multipath channel characteristics play a key role in determining communication performance This paper reviews recent research findings concerning antennas and propagation in MIMO systems Issues considered include channel capacity computation, channel measurement and modeling approaches, and the impact of antenna element properties and array configuration on system performance Throughout the discussion, outstanding research questions in these areas are highlighted

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A review of antennas and propagation for MIMO wireless communications

A ray-shooting approach is presented for calculating the interior radar cross section (RCS) from a partially open cavity. In the problem considered, a dense grid of rays is launched into the cavity through the opening. The rays bounce from the cavity walls based on the laws of geometrical optics and eventually exit the cavity via the aperture. The ray-bouncing method is based on tracking a large number of rays launched into the cavity through the opening and determining the geometrical optics field associated with each ray by taking into consideration: (1) the geometrical divergence factor, (2) polarization, and (3) material loading of the cavity walls. A physical optics scheme is then applied to compute the backscattered field from the exit rays. This method is so simple in concept that there is virtually no restriction on the shape or material loading of the cavity. Numerical results obtained by this method are compared with those for the modal analysis for a circular cylinder terminated by a PEC plate. RCS results for an S-bend circular cylinder generated on the Cray X-MP supercomputer show significant RCS reduction. Some of the limitations and possible extensions of this technique are discussed. >

Shooting and bouncing rays: calculating the RCS of an arbitrarily shaped cavity

Introduction: radar electronic backscattering radar signals radar ambiguity function and matched filter synthetic aperture radar imaging Time-frequency transforms: linear transforms bilinear transforms Detection and extraction of signal noise: time-varying frequency filtering SNR improvement in time-frequency domain CFAR detection in joint time-frequency domain signal extraction in joint time-frequency domain Time-frequency analysis of radar range profiles: electromagnetic phenomenology embedded in backscattered data time-frequency representation of range profiles application of high-resolution time-frequency techniques to scattering data extraction of dispersive scattering features from radar imagery using time-frequency processing Time-frequency based image formation: radar imaging of moving targets motion compensation time-frequency based image formation radar imaging of manoeuvring targets radar imaging of multiple targets Motion compensation in inverse synthetic aperture radar imaging using time-frequency techniques: motion compensation algorithms time-frequency based motion compensation motion compensation examples of simulated and measured data presence of three-dimensional target motion Synthetic aperture radar imaging of moving target: radar signatures of moving targets effect of target motion on SAR imaging detection and imaging of moving targets SAR imaging of moving targets using time-frequency transforms Time-frequency transform for analysis of micro-doppler phenomena: vibration induced micro-doppler rotation induced micro-doppler examples Trends in time-frequency transforms for radar applications

Time-Frequency Transforms for Radar Imaging and Signal Analysis

The feasibility of classifying different human activities based on micro-Doppler signatures is investigated. Measured data of 12 human subjects performing seven different activities are collected using a Doppler radar. The seven activities include running, walking, walking while holding a stick, crawling, boxing while moving forward, boxing while standing in place, and sitting still. Six features are extracted from the Doppler spectrogram. A support vector machine (SVM) is then trained using the measurement features to classify the activities. A multiclass classification is implemented using a decision-tree structure. Optimal parameters for the SVM are found through a fourfold cross-validation. The resulting classification accuracy is found to be more than 90%. The potentials of classifying human activities over extended time duration, through wall, and at oblique angles with respect to the radar are also investigated and discussed.

Human Activity Classification Based on Micro-Doppler Signatures Using a Support Vector Machine

A novel approach for inverse synthetic aperture radar (ISAR) imaging is presented for both target translational motion and rotational motion nonuniformity compensation. The basic idea is to perform Doppler tracking to individual scatterers via an adaptive joint time-frequency (AJTF) projection technique. After maximizing the projection of the phase function to a set of basis functions in time-frequency plane, the Doppler frequency drift of the strongest scatterer in the range bin is automatically tracked out and the multiple prominent point processing (PPP) scheme is implemented to eliminate both the translational motion error and rotational motion nonuniformity. Further the azimuth spacing can be estimated, which permits polar reformatting of the original collected data.

ISAR motion compensation via adaptive joint time-frequency technique

The problem of feature extraction from inverse synthetic aperture radar (ISAR) data collected from targets with rotating parts is addressed. In traditional ISAR imaging, rigid-body motion is usually assumed. When non-rigid-body motions are present, it is not possible to obtain a focused image of both the target and the rotating part. To solve this problem, the radar signal is first parameterised using the adaptive chirplet signal representation. The signal from the body and that from the rotating part are then separated in the parameter space. Point-scatterer simulation results show that better geometrical features of the body and better micro-Doppler features of the rotating part can be extracted after the separation. The algorithm is also demonstrated using the measurement data from an in-flight aircraft and a walking person.

Hao Ling

Papers

Shooting and bouncing rays: calculating the RCS of an arbitrarily shaped cavity

Time-Frequency Transforms for Radar Imaging and Signal Analysis

Human Activity Classification Based on Micro-Doppler Signatures Using a Support Vector Machine

ISAR motion compensation via adaptive joint time-frequency technique

Application of adaptive chirplet representation for ISAR feature extraction from targets with rotating parts