SangHyun Chang

A short-range UWB impulse-radio CMOS sensor for human feature detection

This paper presents a wireless non-contact sensor that enables detection, localization, and monitoring of people along with their specific features such as gait and cardiopulmonary activities. These types of sensors can be embedded in the environment and networked with the existing wireless infrastructure to create an intelligent and responsive ambient where the health of children, patients, and the elderly can be monitored without intrusion. None of the common sensing modalities including visible optical, infra-red, and ultra-sound can operate under different visibility conditions, without Line-Of-Sight (LOS), under environmental noise, and measure human-specific features simultaneously. Radio Frequency (RF) sensors have been used to localize humans, and monitor their gait and vital signs [1,2]. Most of these RF sensors transmit a Continuous Wave (CW) modulated or un-modulated waveform and detect the Doppler shift caused by the movement of hearts, lungs, and other body parts — the latter referred to as micro-Doppler technique. RF sensors do not require LOS and work under extreme weather and visibility conditions.

An algorithm for UWB radar-based human detection

This paper presents an algorithm for human presence detection in urban environments using an ultra-wide-band (UWB) impulse-based mono-static radar. A specular multi-path model (SMPM) is used to characterize human body scattered UWB waveforms. The SMPM parameters are used within a classical likelihood ratio detector framework to detect the presence of humans via gait, with the aid of a multi-target tracking technique (MTT). Experimental results on a simple human gait detection problem in an outdoor urban environment are presented to illustrate and validate the approach.

People Tracking with UWB Radar Using a Multiple-Hypothesis Tracking of Clusters (MHTC) Method

This paper presents a method to track multiple moving humans using Ultra-Wideband (UWB) radar. UWB radar can complement other human tracking technologies, as it works well in poor visibility conditions. Our tracking approach is based on a point process interpretation of the multi-path UWB radar scattering model for moving humans. Based on this model, we present a multiple hypothesis tracking (MHT) framework for tracking the ranges and velocities of a variable number of moving human targets. The multi-target tracking (MTT) problem for UWB radar differs from traditional applications because of the complex multipath scattering observations per target. We develop an MHT framework for UWB radar-based multiple human target tracking, which can simultaneously solve the complex observation clustering and data association problems using Bayesian inference. We present experimental results in which a monostatic UWB radar tracks both individual and multiple human targets to estimate target ranges and velocities, even with changing numbers of targets across radar scans.

Human detection and tracking via Ultra-Wideband (UWB) radar

This paper presents an algorithm for human presence detection and tracking using an Ultra-Wideband (UWB) impulse-based mono-static radar. UWB radar can complement other human tracking technologies, as it works well in poor visibility conditions. UWB electromagnetic wave scattering from moving humans forms a complex returned signal structure which can be approximated to a specular multi-path scattering model (SMPM). The key technical challenge is to simultaneously track multiple humans (and non-humans) using the complex scattered waveform observations. We develop a multiple-hypothesis tracking (MHT) framework that solves the complicated data association and tracking problem for an SMPM of moving objects/targets. Human presence detection utilizes SMPM signal features, which are tested in a classical likelihood ratio (LR) detector framework. The process of human detection and tracking is a combination of the MHT method and the LR human detector. We present experimental results in which a mono-static UWB radar tracks human and non-human targets, and detects human presence by discerning human from moving non-human objects.

UWB radar-based human target tracking

This paper presents a framework and algorithms for tracking the range of moving humans via a mono-static ultra-wideband (UWB) radar. The approach is based on a specular multi-path model for UWB radar scatters from walking humans. Empirical studies show that multipath time-of-arrival (TOA) can be modeled as a point process whose behavior is governed by a Gamma distribution. Based on this insight, we develop a tracking procedure that combines a Kalman Filter with a point process observation model whose measurements are processed with an Expectation-Maximization (EM) procedure. As a byproduct, the EM procedure solves the multi-target data segmentation and data association problems. We present experimental results in which a monostatic UWB radar tracks both individual and up to two human targets.

UWB human detection radar system: A RF CMOS chip and algorithm integrated sensor

This paper presents a radio frequency (RF) CMOS chip and algorithm integrated solution of an Ultra-Wideband (UWB) Impulse-Radio (IR) radar system for human presence detection and tracking. UWB radar can complement other human detection and tracking technologies, as it works well in poor visibility conditions with high time/depth-resolution. UWB radar response provides the complex multipath scattering characteristics in each scan, as well as the high sensitive variation in dynamic observation patterns between scans to pose challenge in designing UWB radar hardware and signal processing algorithm. We develop a UWB IR CMOS human feature detection radar transceiver chip and human presence detection algorithm. Thereafter, we integrated the UWB CMOS radar chip and the algorithm through UWB sensor module, and tested the integrated system in a simple outdoor environment to validate the performance of the integrated system. We present experimental results in which the integrated UWB human detection radar system tracks human and non-human targets, and detects human presence by discerning human from moving non-human objects robustly using human feature extraction and likelihood ratio testing (LRT).

Polarization measurements in a UWB multipath channel

The polarization effects in an ultra-wideband (UWB) propagation channel can be studied with arrays of propagation measurements. An approach to estimate the polarization is presented for the single-path channel. For the multi-path channel, an array signal processing algorithm (the sensor-CLEAN algorithm) was applied to array measurement data to decompose a received waveform with a dense multi-path profile into its component single-path signals. This algorithm was tested on a 3 /spl times/ 3 /spl times/ 3 array of UWB propagation measurements for three receiving antenna orientations. An estimation algorithm was constructed to characterize time-of-arrival, angle-of-arrival, waveform shape and polarization of each resolvable waveform in the composite received signal. A modified channel propagation model was proposed to include the polarization characteristics. The suggested channel model with estimated parameters was applied to estimate the received waveform for a different antenna orientation. The estimated waveform was compared with a measured waveform to verify the polarization estimation algorithm and the modified channel model including polarization characteristics.

An MHT algorithm for UWB radar-based multiple human target tracking

This paper presents a multiple hypothesis tracking (MHT) framework for tracking the ranges and velocities of a variable number of moving human targets via a mono-static ultra-wideband (UWB) radar. The multi-target tracking (MTT) problem for UWB radar-based human target tracking differs from traditional applications because of the multitude of observations (multipath scattering) per target in each scan, due to the short spatial extent of the transmitted UWB signal pulse width. We develop an MHT framework for UWB radar-based multiple human target tracking that extends a previously studied human tracking algorithm. We present experimental results in which a monostatic UWB radar tracks both individual and multiple human targets, even with changing numbers of targets across radar scans.

UWB wave polarization measurements in an indoor channel using array sensors

In this paper, UWB polarization measurements with a multipath decomposition process is studied with an array of propagation measurements using three receiving antenna orientations. In order to estimate each of the decomposed impinging electric field at a receiving location in the multipath channel, a modified version of the sensor-CLEAN algorithm is applied to the array measurements in combination with the estimation method. The fidelity of the combined estimation process with array measurements is verified by comparison between the measured and estimated signal waveforms for a reoriented receiving antenna.