UWB Radar Research Articles

Nested sparse sampling and co-prime sampling in sense-through-foliage target detection

This paper firstly introduces nested sampling and co-prime sampling, which were proposed recently, but have never been applied to real world target detection. We apply nested sampling and co-prime sampling to target detection in UWB radar sensor networks (RSN), based on a differential approach. The non-stationary UWB signal needs to be decomposed into several approximate wide sense stationary (WSS) signals so that nested sampling could be used in this situation. We also compare the performance of nested sampling and co-prime sampling against uniform under-sampling. The results show that in terms of good quality data and poor quality data, both nested sampling and co-prime sampling work better.

Techniques for Clutter Suppression in the Presence of Body Movements during the Detection of Respiratory Activity through UWB Radars

This paper focuses on the feasibility of tracking the chest wall movement of a human subject during respiration from the waveforms recorded using an impulse-radio (IR) ultra-wideband radar. The paper describes the signal processing to estimate sleep apnea detection and breathing rate. Some techniques to solve several problems in these types of measurements, such as the clutter suppression, body movement and body orientation detection are described. Clutter suppression is achieved using a moving averaging filter to dynamically estimate it. The artifacts caused by body movements are removed using a threshold method before analyzing the breathing signal. The motion is detected using the time delay that maximizes the received signal after a clutter removing algorithm is applied. The periods in which the standard deviations of the time delay exceed a threshold are considered macro-movements and they are neglected. The sleep apnea intervals are detected when the breathing signal is below a threshold. The breathing rate is determined from the robust spectrum estimation based on Lomb periodogram algorithm. On the other hand the breathing signal amplitude depends on the body orientation respect to the antennas, and this could be a problem. In this case, in order to maximize the signal-to-noise ratio, multiple sensors are proposed to ensure that the backscattered signal can be detected by at least one sensor, regardless of the direction the human subject is facing. The feasibility of the system is compared with signals recorded by a microphone.

Design, Realization, and Test of a UWB Radar Sensor for Breath Activity Monitoring

An analytical model of an ultrawideband range gating radar is developed. The model is used for the system design of a radar for breath activity monitoring having sub-millimeter movement resolution and fulfilling the requirements of the Federal Communications Commission in terms of effective isotropic radiated power. The system study has allowed to define the requirements of the various radar subsystems that have been designed and realized by means of a low cost hybrid technology. The radar has been assembled and some performance factors, such as range and movement resolution, and the receiver conversion factor have been experimentally evaluated and compared with the model predictions. Finally, the radar has been tested for remote breath activity monitoring, showing recorded respiratory signals in very good agreement with those obtained by means of a conventional technique employing a piezoelectric belt.

Performances of Micropower UWB Radar Using Orthogonal Waveforms

Radars and their applications were, for a long time, reserved to national defense, air security or weather service domains. For a few years, with the emergence of new technologies, radar applications have been developed and have become known in the civil domain. In particular, the arrival of UWB—Ultra-Wideband technology allows the design of compact and low-cost radars with multiple fields of application. In this paper, we focus on road applications, such as driving assistance with the objective of increasing safety and reducing accidents. In classical UWB radar systems, Gaussian and monocycle pulses are commonly used. In previous works, original waveforms based on orthogonal functions (Hermite and Gegenbauer) were proposed. These provide a good spatial resolution, suitable for radar detection. Another advantage of these waveforms is their multiple access capability, due to their orthogonality. The aim of the study presented in this article is to compare simulation and experimental results obtained, especially for short-range anticollision radar application, using these waveforms in one part and Gaussian and monocycle pulses in the other part. The originality of this paper relies on the new approach. Indeed, this comparison study using these waveforms has never been done before. Finally, some examples of real experiments in a real road environment with different waveforms are presented and analysed.

A novel handheld pseudo random coded UWB radar for human sensing applications

A novel handheld pseudo random coded UWB radar for human sensing applications

Sense-through-wall human detection using the UWB radar with sparse SVD

In this paper, a method for through-wall human detection based on the singular values decomposition of the measurement matrices is presented. After demonstrating the sparsity of the matrices using the CLEAN algorithm, an SVD algorithm based on the Lanczos process is applied to compute their singular values. We also analyze the singular values of matrices constructed by difference square techniques for different types of walls and compare our algorithm with a 2-D imaging approach proposed by researchers in Time Domain Company. Detection results show that our method performs well in the gypsum wall, brick wall, and wooden door.

Simulation and manufacturing of a miniaturized exponential UWB TEM horn antenna for UWB radar applications

This paper presents the parameterization of the structure of a miniaturized exponential UWB TEM horn antenna and its effect on the matching impedance and directivity. In addition, a microstrip balun that feeds the antenna was proposed in order to improve the balance, and the return loss for low frequencies. Both the antenna and the microstrip balun were simulated to obtain a final high performance model to be manufactured at a later time. The proposed antenna operates in a frequency range from 3.2 GHz to 7.5 GHz, meeting the standards established by the FCC and the ETSI for ultra-wideband technology. Moreover, based on these characteristics, the antenna have many UWB radar applications such as monitoring of structures (buildings, bridges, etc.), anti-collision radar, vital signs detection, and long-distance communications, as a result of its high gain around 15 dB.

Investigation of Localization Accuracy for UWB Radar Operating in Complex Environment

Investigation of Localization Accuracy for UWB Radar Operating in Complex Environment

Combined adaptive up-and-down method for equivalent time signal transformation

A combined adaptive up-and-down method for comparator type equivalent time transformation is proposed. The method uses the signal increment at the preceding phase point of the signal as well as the data for the current signal phase. The efficiency of the proposed method is compared to those of other comparator type equivalent time methods. The method is investigated for implementation in UWB radars.

Efficient Three-Dimensional Imaging Method Based on Enhanced Range Point Migration for UWB Radars

Ultrawideband pulse radar has a definite advantage over optical ranging techniques in harsh optical environments, such as a dark smog or strong backlight. In security or rescue situations with blurry visibility, it is particularly promising for identifying human bodies. One of the most promising approaches for this type of application is the recently proposed range point migration (RPM) method, which is beneficial for nonparametric imaging and is robust in noisy or heavy interference situations. However, the original RPM requires a discretization of the direction-of-arrival variables in its search operation. The resulting coarse discretization seriously degrades the imaging accuracy, particularly for 3-D problems and far-field observations. Consequently, in this approach, there is a major tradeoff between the amount of computation and accuracy. To overcome this difficulty, this letter proposes a more efficient RPM method, where the extraction of the point of intersection of spheres is adopted. A distinct advantage of this method is that the accuracy is basically invariant to the observation range when avoiding the aforementioned discretization. Numerical simulations including noisy cases prove that our proposed RPM significantly reduces the computation complexity while retaining imaging accuracy.

Non-orthogonal Sidelobes Reduction for Virtual Aperture UWB Radar

Non-orthogonal Sidelobes Reduction for Virtual Aperture UWB Radar

SU‐E‐J‐62: Theoretical Investigation of Ultra‐WideBand (UWB) Penetration Through Biological Tissues

Purpose: The UWB is a radio‐frequency electromagnetic pulse with width around nanosecond encompassing 3.1–10.6 GHz frequencies. The UWB is currently used in remote sensing as through‐the‐wall imaging technology. To develop this technology into through‐the‐body tumor‐detection technology, first, we theoretically investigate whether the UWB pulses can penetrate through human tissues such as skin, muscle, bone, fat, and lung. Specifically we want to calculate which frequencies can penetrate deeper through human tissues. Methods: We theoretically relate the complex permittivity with the complex index of refraction and obtain the reflection and transmission coefficients for skin, muscle, bone, fat, and lung. We use an experimentally‐measured complex permittivity from the published source1 as input to our numerical model. We calculate 1/e penetration depth, which is equivalent to 36.7% of initial radar power, for each frequency, from air to each tissue as an indicator of penetration capability of the UWB. Results: Our results show that lower UWB frequency (3 GHz) is better at penetrating through the human tissues than higher frequency (10 GHz). We find 1/e penetration depth for human skin, muscle, fat, bone, and lung to be 4.45, 4.67, 0.49, 2.61, and 2.38 cm for 3 GHz, respectively. At 10 GHz, the 1/e penetration depths are reduced significantly to 0.17, 0.13, 0.33, 0.21, 0.19 cm, respectively. This Result indicates that it is better to design a UWB radar system with higher power at lower frequencies. Conclusion: We find that lower frequencies of the UWB can penetrate deeper into human tissues. This Result will be used to design a future experiment for further investigation of the UWB radar as a new modality for lung‐tumor detection.1. Gabriel et al. The dielectric properties of biological tissues: I. Literature survey Phys. Med. Biol. 41(11) 2231‐2249

3D imaging by fast deconvolution algorithm in short-range UWB radar for concealed weapon detection

A fast imaging algorithm for real-time use in short-range (ultra-wideband) radar with synthetic or real-array aperture is proposed. The reflected field is presented here as a convolution of the target reflectivity and point spread function (PSF) of the imaging system. To obtain a focused 3D image, the proposed algorithm deconvolves the PSF out from the acquired data volume with high speed due to fast Fourier transform and implementation in frequency-wavenumber domain. Then the result is tested against two numerical criteria for efficiency, namely error and instability, whose optimal values can be obtained iteratively. Since the PSF differs with distance, the algorithm suits mainly applications with relatively small objects such as concealed weapon detection. Using several PSFs allows us to image a certain range of interest by their successive deconvolution from the same data. Performance of the algorithm has been evaluated experimentally and compared with that of Kirchhoff migration. Measurements were carried out by a 5–25 GHz synthetic aperture radar in the lab, and scenarios included a gun and a ceramic knife in free space, on a large metal plate, and a gun concealed on a dummy under a thick raincoat. The results demonstrate sufficient image quality obtained in a fraction of time.

UWB Based Detection with Fractional Fourier Transform

The importance of UWB radar system for indoor applications is of keen interest. Applications such as across the wall monitoring, through wall detection, intrusion detection and under rubble vital sign detection are of cumulative interest and are also used in modern rescue systems to help the trapped human beings, along with detection and activity monitoring across the wall. In this paper we have studied across the wall detection of presence of different objects by applying the fractional Fourier transform. Computer aided design based simulations for indoor environment are accomplished by using finite difference time domain solution for Maxwell’s equations. Finally, fractal analysis is realized for the collected signals reflected from the objects present across the wall.

Anomaly detection in big data from UWB radars

AbstractThe definitions of big data and anomaly detection are presented. The theory of ultra‐wideband radar and the through‐wall detection of a human model based on ultra‐wideband radar are briefly introduced. The target criterion with wavelet packet transform is deduced, and the procedure for the through‐wall human detection with statistical process control is constructed. The radar echo signals are collected at stationary and moving statuses of a human being for three types of walls. The experimental results demonstrate the effective of through‐wall target detection based on the proposed algorithm. Copyright © 2013 John Wiley & Sons, Ltd.

Human-Target Detection and Surrounding Structure Estimation Under a Simulated Rubble via UWB Radar

The presence of a human target and the surrounding rubble structure are both important information in postdisaster rescue. In this letter, we study the signal-processing algorithm for detecting a human target in radar echo data. Furthermore, a solution is proposed to estimate the surrounding structure-the distance between the human target and the top wall of the cavity where the human target is trapped. In the latter procedure, the human position estimated before is used as a prior knowledge. In order to verify the feasibility of the proposed method, experiments are carried out with a human subject lying under the simulated rubble structure. The results show prospects of the proposed method.

3D detection of automobile scattering centers using UWB radar sensors at 24/77 GHz

Scattering centers of two different vehicles have been evaluated using SAR, and the combination of SAR and DBF. The results show that main scattering centers are located at the wheels, the regions around the license plate, door outer panel, windshield pillar, center pillar, rear pillar, and light units. Furthermore, it has been shown that multipath propagation enables an indirect detection of scattering centers. The analysis shows no significant differences between the scattering center locations at 24 GHz and 77 GHz. However, the increased bandwidth at 77 GHz allows resolving merged scattering centers and improves the contour determination. The comparison between the measurement results of the SAR processing and the mechanical scanning radar confirmed similar main scattering centers. Furthermore, the measurement results show that the contour and orientation of a vehicle can be determined at a distance of 10 m with a bandwidth of 2 GHz and an angular resolution of approximately 2°.

UWB RADAR based Modified Adaptive CFAR Algorithm for improved safety of Personal Rapid Transit

UWB RADAR based Modified Adaptive CFAR Algorithm for improved safety of Personal Rapid Transit

Detection of Underwater Carrier-Free Pulse based on Time-Frequency Analysis

Carrier-free short pulse widely employed in UWB radar is brought into high-resolution sonar system, which has unique advantages: attaining more target information, restraining fluctuation of reverberation envelop efficiently in short-range detection and achieving accurate estimation. In essence such pulse is transiently short in time domain and wide in frequency domain, and as such it is difficult to separate signal to noise based on Fourier Transform spectrum. So as to seek for detection methods of short pulse, minor differences of energy distribution of time-frequency characteristics are presented on three time-frequency methods such as Short Time Fourier Transform, Wavelet Transform and Hilbert-Huang Transform. With these results, a tri-channel detector is established for such underwater short pulse in noise environment, which is generally suitable not only for detection module of underwater sonar system but also that of radar system.

Passive Microwave Component Design Using Inverse Scattering: Theory and Applications

We briefly review different synthesis techniques for the design of passive microwave components with arbitrary frequency response, developed by our group during the last decade. We provide the theoretical foundations based on inverse scattering and coupled-mode theory as well as several applications where the devices designed following those techniques have been successfully tested. The main characteristics of these synthesis methods are as follows. (a) They are direct, because it is not necessary to use lumped-element circuit models; just the target frequency response is the starting point. (b) They are exact, as there is neither spurious bands nor degradation in the frequency response; hence, there is no bandwidth limitation. (c) They are flexible, because they are valid for any causal, stable, and passive transfer function; only inviolable physical principles must be guaranteed. A myriad of examples has been presented by our group in many different technologies for very relevant applications such as harmonic control of amplifiers, directional coupler with enhanced directivity and coupling, transmission-type dispersive delay lines for phase engineering, compact design of high-power spurious free low-pass waveguide filters for satellite payloads, pulse shapers for advanced UWB radar and communications and for novel breast cancer detection systems, transmission-typeNth-order differentiators for tunable pulse generation, and a robust filter design tool.