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20 pages, 884 KiB

Open AccessArticle

A GDOP-Based Performance Description of TOA Localization with Uncertain Measurements

by Yao Wang, Tao Zhou, Wei Yi and Lingjiang Kong

Remote Sens. 2022, 14(4), 910; https://0-doi-org.brum.beds.ac.uk/10.3390/rs14040910 - 14 Feb 2022

Cited by 11 | Viewed by 1472

In this paper, we study a geometric dilution of a precision (GDOP)-based localization performance metric for multisite radar adopting a time-of-arrival (TOA)-based localization scheme. In contrast to the existing literature, we consider an actual uncertain measurement situation where the detection probabilities of radar [...] Read more.

In this paper, we study a geometric dilution of a precision (GDOP)-based localization performance metric for multisite radar adopting a time-of-arrival (TOA)-based localization scheme. In contrast to the existing literature, we consider an actual uncertain measurement situation where the detection probabilities of radar nodes are assumed to be less than unity. The aim is to formulate a general signal-decoupled metric to describe the system localization performance while fully considering detection and estimation operations. Specifically, to match the uncertain measurements, we first establish effectively detected time delay measurements (TDMs) for localization and modify the traditional performance bounds for TDM estimation. Then, by combining the localization performance with the effective detection (ED) via probability, we propose a novel geometric dilution of precision with uncertain measurements (GDOP-UM) metric. The proposed metric can truly characterize the localization performance under the uncertain measurement situation. Finally, the simulation results show that the proposed GDOP-UM can describe the actual localization performance regardless of how the detection performance changes. Full article

(This article belongs to the Special Issue Applications and New Trends in Metrology for Radar/LiDAR-Based Systems)

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18 pages, 25484 KiB

Open AccessArticle

Railway Track Recognition Based on Radar Cross-Section Statistical Characterization Using mmWave Radar

by Shuo Li, Jieqiong Ding, Weirong Liu, Heng Li, Feng Zhou and Zhengfa Zhu

Remote Sens. 2022, 14(2), 294; https://0-doi-org.brum.beds.ac.uk/10.3390/rs14020294 - 10 Jan 2022

Cited by 2 | Viewed by 1970

Abstract

The track settlement has a great influence on the safe operation of high-speed trains. The existing track settlement measurement approach requires sophisticated or expensive equipments, and the real-time performance is limited. To address the issue, an ultra-high resolution track settlement detection method is [...] Read more.

The track settlement has a great influence on the safe operation of high-speed trains. The existing track settlement measurement approach requires sophisticated or expensive equipments, and the real-time performance is limited. To address the issue, an ultra-high resolution track settlement detection method is proposed by using millimeter wave radar based on frequency modulated continuous wave (FMCW). Firstly, by constructing the RCS statistical feature data set of multiple objects in the track settlement measurement environment, a directed acyclic graph-support vector machine (DAG-SVM) based method is designed to solve the problem of track recognition in multi-object scenes. Then, the adaptive chirp-z-transform (ACZT) algorithm is used to estimate the distance between the radar and the track surface, which realizes automatic real-time track settlement detection. An experimental platform has been constructed to verify the effectiveness of the proposed method. The experimental results show that the accuracy of track classification and identification is at least 95%, and the accuracy of track settlement measurement exceeds 0.5 mm, which completely meets the accuracy requirements of the railway system. Full article

(This article belongs to the Special Issue Applications and New Trends in Metrology for Radar/LiDAR-Based Systems)

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20 pages, 5908 KiB

Open AccessArticle

Phase Shift Migration with Modified Coherent Factor Algorithm for MIMO-SAR 3D Imaging in THz Band

by Guan Yang, Chao Li, Shiyou Wu, Shen Zheng, Xiaojun Liu and Guangyou Fang

Remote Sens. 2021, 13(22), 4701; https://0-doi-org.brum.beds.ac.uk/10.3390/rs13224701 - 20 Nov 2021

Cited by 8 | Viewed by 2778

Abstract

In multiple-input-multiple-output synthetic aperture radar (MIMO-SAR) systems, sparse arrays are usually applied, resulting in increased sidelobes of the point spread function. In this paper, a phase shift migration (PSM) imaging algorithm based on the explosion reflection model with modified coherent factor was proposed [...] Read more.

In multiple-input-multiple-output synthetic aperture radar (MIMO-SAR) systems, sparse arrays are usually applied, resulting in increased sidelobes of the point spread function. In this paper, a phase shift migration (PSM) imaging algorithm based on the explosion reflection model with modified coherent factor was proposed for sidelobe suppression in MIMO-SAR three-dimensional (3D) imaging application. By defining the virtual difference wavenumber, reconstructing the raw echo by data rearrangement in wavenumber domain, the original coherent factor algorithm operating in spatial domain can be achieved by the PSM algorithm frame in the wavenumber domain, which means two orders of magnitude increase in computational efficiency. The correctness of the theory is verified by simulation. Finally, a bistatic prototype imaging system in the 0.3 THz band was designed for the proof-of-principle experiments. The experimental results show that the proposed algorithm has a 0.948 structural similarity value to the original coherent factor back-projection algorithm (CF-BPA) which means comparable image quality with much superior efficiency. Full article

(This article belongs to the Special Issue Applications and New Trends in Metrology for Radar/LiDAR-Based Systems)

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18 pages, 595 KiB

Open AccessArticle

Adaptive Waveform Design with Multipath Exploitation Radar in Heterogeneous Environments

by Seden Hazal Gulen Yilmaz, Chiara Zarro, Harun Taha Hayvaci and Silvia Liberata Ullo

Remote Sens. 2021, 13(9), 1628; https://0-doi-org.brum.beds.ac.uk/10.3390/rs13091628 - 21 Apr 2021

Cited by 4 | Viewed by 2185

Abstract

The problem of detecting point like targets over a glistening surface is investigated in this manuscript, and the design of an optimal waveform through a two-step process for a multipath exploitation radar is proposed. In the first step, a non-adaptive waveform is transmitted [...] Read more.

The problem of detecting point like targets over a glistening surface is investigated in this manuscript, and the design of an optimal waveform through a two-step process for a multipath exploitation radar is proposed. In the first step, a non-adaptive waveform is transmitted and a constrained Generalized Likelihood Ratio Test (GLRT) detector is deduced at reception which exploits multipath returns in the range cell under test by modelling the target echo as a superposition of the direct plus the multipath returns. Under the hypothesis of heterogeneous environments, thus by assuming a compound-Gaussian distribution for the clutter return, this latter is estimated in the range cell under test through the secondary data, which are collected from the out-of-bin cells. The Fixed Point Estimate (FPE) algorithm is applied in the clutter estimation, then used to design the adaptive waveform for transmission in the second step of the algorithm, in order to suppress the clutter coming from the adjacent cells. The proposed GLRT is also used at the end of the second transmission for the final decision. Extensive performance evaluation of the proposed detector and adaptive waveform for various multipath scenarios is presented. The performance analysis prove that the proposed method improves the Signal-to-Clutter Ratio (SCR) of the received signal, and the detection performance with multipath exploitation. Full article

(This article belongs to the Special Issue Applications and New Trends in Metrology for Radar/LiDAR-Based Systems)

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20 pages, 3706 KiB

Open AccessArticle

Adaptive 3D Imaging for Moving Targets Based on a SIMO InISAR Imaging System in 0.2 THz Band

by Hongwei Li, Chao Li, Shiyou Wu, Shen Zheng and Guangyou Fang

Remote Sens. 2021, 13(4), 782; https://0-doi-org.brum.beds.ac.uk/10.3390/rs13040782 - 20 Feb 2021

Cited by 11 | Viewed by 2214

Abstract

Terahertz (THz) imaging technology has received increased attention in recent years and has been widely applied, whereas the three-dimensional (3D) imaging for moving targets remains to be solved. In this paper, an adaptive 3D imaging scheme is proposed based on a single input [...] Read more.

Terahertz (THz) imaging technology has received increased attention in recent years and has been widely applied, whereas the three-dimensional (3D) imaging for moving targets remains to be solved. In this paper, an adaptive 3D imaging scheme is proposed based on a single input and multi-output (SIMO) interferometric inverse synthetic aperture radar (InISAR) imaging system to achieve 3D images of moving targets in THz band. With a specially designed SIMO antenna array, the angular information of the targets can be determined using the phase response difference in different receiving channels, which then enables accurate tracking by adaptively adjusting the antenna beam direction. On the basis of stable tracking, the high-resolution imaging can be achieved. A combined motion compensation method is proposed to produce well-focused and coherent inverse synthetic aperture radar (ISAR) images from different channels, based on which the interferometric imaging is performed, thus forming the 3D imaging results. Lastly, proof-of-principle experiments were performed with a 0.2 THz SIMO imaging system, verifying the effectiveness of the proposed scheme. Non-cooperative moving targets were accurately tracked and the 3D images obtained clearly identify the targets. Moreover, the dynamic imaging results of the moving targets were achieved. The promising results demonstrate the superiority of the proposed scheme over the existing THz imaging systems in realizing 3D imaging for moving targets. The proposed scheme shows great potential in detecting and monitoring moving targets with non-cooperative movement, including unmanned military vehicles and space debris. Full article

(This article belongs to the Special Issue Applications and New Trends in Metrology for Radar/LiDAR-Based Systems)

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20 pages, 12177 KiB

Open AccessArticle

Performance Evaluation of Vibrational Measurements through mmWave Automotive Radars

by Gianluca Ciattaglia, Adelmo De Santis, Deivis Disha, Susanna Spinsante, Paolo Castellini and Ennio Gambi

Remote Sens. 2021, 13(1), 98; https://0-doi-org.brum.beds.ac.uk/10.3390/rs13010098 - 30 Dec 2020

Cited by 18 | Viewed by 3363

Abstract

Thanks to the availability of a significant amount of inexpensive commercial Frequency Modulated Continuous Wave Radar sensors, designed primarily for the automotive domain, it is interesting to understand if they can be used in alternative applications. It is well known that with a [...] Read more.

Thanks to the availability of a significant amount of inexpensive commercial Frequency Modulated Continuous Wave Radar sensors, designed primarily for the automotive domain, it is interesting to understand if they can be used in alternative applications. It is well known that with a radar system it is possible to identify the micro-Doppler feature of a target, to detect the nature of the target itself (what the target is) or how it is vibrating. In fact, thanks to their high transmission frequency, large bandwidth and very short chirp signals, radars designed for automotive applications are able to provide sub-millimeter resolution and a large detection bandwidth, to the point that it is here proposed to exploit them in the vibrational analysis of a target. The aim is to evaluate what information on the vibrations can be extracted, and what are the performance obtainable. In the present work, the use of a commercial Frequency Modulated Continuous Wave radar is described, and the performances achieved in terms of displacement and vibration frequency measurement of the target are compared with the measurement results obtained through a laser vibrometer, considered as the reference instrument. The attained experimental results show that the radar under test and the reference laser vibrometer achieve comparable outcomes, even in a cluttered scenario. Full article

(This article belongs to the Special Issue Applications and New Trends in Metrology for Radar/LiDAR-Based Systems)

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25 pages, 80027 KiB

Open AccessArticle

Perspectives on the Structural Health Monitoring of Bridges by Synthetic Aperture Radar

by Filippo Biondi, Pia Addabbo, Silvia Liberata Ullo, Carmine Clemente and Danilo Orlando

Remote Sens. 2020, 12(23), 3852; https://0-doi-org.brum.beds.ac.uk/10.3390/rs12233852 - 24 Nov 2020

Cited by 25 | Viewed by 4068

Abstract

Large infrastructures need continuous maintenance because of materials degradation due to atmospheric agents and their persistent use. This problem makes it imperative to carry out persistent monitoring of infrastructure health conditions in order to guarantee maximum safety at all times. The main issue [...] Read more.

Large infrastructures need continuous maintenance because of materials degradation due to atmospheric agents and their persistent use. This problem makes it imperative to carry out persistent monitoring of infrastructure health conditions in order to guarantee maximum safety at all times. The main issue of early warning infrastructure fault detection is that expensive in-situ distributed monitoring sensor networks have to be installed. On the contrary, the use of satellite data has made it possible to use immediate and low-cost techniques in recent years. In this regard, the potential of spaceborne Synthetic Aperture Radar for the monitoring of critical infrastructures is demonstrated in geographically extended areas, even in the presence of clouds, and in really tough weather. A complete procedure for damage early-warning detection is designed, by using micro-motion (m-m) estimation of critical sites, based on modal proprieties analysis. Particularly, m-m is processed to extract modal features such as natural frequencies and mode shapes generated by vibrations of large infrastructures. Several study cases are here considered and the “Morandi” Bridge (Polcevera Viaduct) in Genoa (Italy) is analyzed in depth highlighting abnormal vibration modes during the period before the bridge collapsed. Full article

(This article belongs to the Special Issue Applications and New Trends in Metrology for Radar/LiDAR-Based Systems)

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Review

Jump to: Research

24 pages, 4226 KiB

Open AccessReview

Hand Gestures Recognition Using Radar Sensors for Human-Computer-Interaction: A Review

by Shahzad Ahmed, Karam Dad Kallu, Sarfaraz Ahmed and Sung Ho Cho

Remote Sens. 2021, 13(3), 527; https://0-doi-org.brum.beds.ac.uk/10.3390/rs13030527 - 02 Feb 2021

Cited by 100 | Viewed by 13062

Abstract

Human–Computer Interfaces (HCI) deals with the study of interface between humans and computers. The use of radar and other RF sensors to develop HCI based on Hand Gesture Recognition (HGR) has gained increasing attention over the past decade. Today, devices have built-in radars [...] Read more.

Human–Computer Interfaces (HCI) deals with the study of interface between humans and computers. The use of radar and other RF sensors to develop HCI based on Hand Gesture Recognition (HGR) has gained increasing attention over the past decade. Today, devices have built-in radars for recognizing and categorizing hand movements. In this article, we present the first ever review related to HGR using radar sensors. We review the available techniques for multi-domain hand gestures data representation for different signal processing and deep-learning-based HGR algorithms. We classify the radars used for HGR as pulsed and continuous-wave radars, and both the hardware and the algorithmic details of each category is presented in detail. Quantitative and qualitative analysis of ongoing trends related to radar-based HCI, and available radar hardware and algorithms is also presented. At the end, developed devices and applications based on gesture-recognition through radar are discussed. Limitations, future aspects and research directions related to this field are also discussed. Full article

(This article belongs to the Special Issue Applications and New Trends in Metrology for Radar/LiDAR-Based Systems)

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