Ultra-wideband Radar System Research Articles

A 3-D High-Order Reverse-Time Migration Method for High-Resolution Subsurface Imaging With a Multistation Ultra-Wideband Radar System

A three-dimensional high-order reverse-time migration (3-D HO-RTM) method is proposed to perform subsurface electromagnetic imaging with an ultra-wideband radar (UWBR) system consisting of a multi-input and multi-output antenna array. By using a UWBR system to collect temporal scattering signals, subsurface targets can be detected, and the image of targets can be obtained by imaging methods such as the back-propagation method, frequency-wavenumber migration technique, time-reversal mirror, and reverse-time migration method. The proposed HO-RTM method is based on the high-order finite-difference time-domain (HO-FDTD) method to significantly reduce the computational cost in the conventional RTM method. The measured data from an experimental lunar exploration system Chang'E-5 have been collected on a 7 m × 2.5 m × 2.5 m laboratory model with volcanic ash and validated by the 3-D HO-RTM method. Results show that all buried objects can be effectively identified by the HO-RTM, and its computer memory and CPU time are only 3.87% and 0.7128% of the conventional RTM method, respectively.

In brief

PAGE 1259 Researchers in China have proposed an unconventional dual-band antenna with two transverse slots etched onto a substrate integrated waveguide (SIW) cavity. The design exhibits good stopband characteristics including significantly improved non-radiating gain and band-edge selectivity. Experimental results verify the effectiveness of the antenna and promote its use in wireless communication applications. PAGE 1302 i-vector based speech recognition frameworks require effective channel compensation methods for enlarging class differences while reducing class variations. Using a discriminatively learned network (DLN) a team of Chinese researchers used both speaker classification and supervising verification signals for identification. The DLN performs better than linear discriminant analysis (LDA) methods. Electric field distributions at different frequencies. PAGE 1298 A large collaboration of researchers from the USA and Qatar report the enhancement of electrical characteristics in thin film transistors (TFTs) by stacking layers with alternating precursor solution concentrations. The mobility of the fabricated alternating-layer TFT was higher than those with only single concentrations. Future work will study the underlying reason for this effect. Similar DNN parameter architecture. PAGE 1292 A novel analytical model of polarimetric dispersion (PD) based on frequency-domain range pulse compression has been analysed and proposed by researchers in China. The simulation results indicate that spaceborne P-band ultra-wideband synthetic aperture radar systems are heavily influenced by PD effects from ionospheric Faraday rotation. Field effect mobility of TFTs at different concentrations. PAGE 1260 A simple internal antenna combining a planar inverted F antenna and a loop antenna to achieve wideband ultra-high frequency operation for digital television applications has been presented by researchers in Korea. The antenna is implementable within T models with sufficiently wide bandwidth and high peak gain to provide good performance. Polarimetric distortion coefficient function with bandwidth. 3D structure of proposed loop antenna.

Measurement of instantaneous heart rate using radar echoes from the human head

The feasibility of measuring heart rate using radar echoes from a human head is demonstrated. Non-contact measurement of vital signs using radar has been attracting much attention because such technologies can breakthrough benefits for monitoring health conditions without electrodes or wearable devices. Most existing studies have measured echoes from the torso, particularly the chest wall. However, this is difficult because of multiple interfering reflections from the complex shape of the torso and other body parts, such as limbs. The current study is the first demonstration that non-contact heart rate measurement can be easily achieved using echoes from the human head. There are two important advantages of measurement from the human head: (i) the simple shape of the head makes an ideal radar target with only a single reflection, and (ii) the other undesired echoes can be removed using time-gating when an ultra-wideband radar is used. Nonetheless, because the displacement of the human head due to heart rate is small, a millimetre-wave ultra-wideband array radar system is developed, which is installed on the ceiling and used in the proposed measurements with participants.

Non-Contact Human Motion Recognition Based on UWB Radar

Human motion recognition is crucial for surveillance, search and rescue operation, smart homes, and senior care. In daily life, there exists various kinds of human motions with widely different characteristics and meanwhile they also exhibit some clustering features, which make it difficult for recognition. In this paper, a multiple-layer classification method is introduced for comprehensive human motion recognition, including the largest number of motion types ever studied with an ultra-wideband radar system. First, in the pre-screening layer, information in the time-range domain is used to distinguish in situ motions and non-in situ motions. According to different kinds of human motions, the weighted range-time-frequency transform method is proposed to obtain corresponding spectrograms. Then physical empirical features and principal component analysis-based features are extracted for the classifiers to achieve the specific in situ and non-in situ motions, respectively. Extensive experiments have been conducted, achieving the highest accuracy rate of up to 94.4% and 95.3% for in situ motions and non-in situ motions, respectively. The interferences of individual diversity on the proposed method are also investigated. The proposed method could be beneficial in smart homes and senior care.

Antenna Effects on Respiratory Rate Measurement Using a UWB Radar System

State-of-the-art advances in the field of radar technology have made it possible to design noninvasive sensing devices of vital signs. This paper presents the effects of antenna characteristics on an ultra-wideband (UWB) radar-based respiratory rate measurement system for tele-health-monitoring applications. The performance of three types of antenna for a UWB radar respiratory rate measurement system was studied in this paper. In this context, the proposed system was comprehensively evaluated using two experimental sets. First, a mechanical setup was used to provide a series of controlled frequency and distance motions for measurement test. The error analysis for various parameters associated with pulmonary activities such as breathing frequency and chest displacement was performed. Results indicated that the proposed sensing system used effectively as a respiratory rate measurement is less affected and shows less error when an antenna with directive radiation pattern, low cross-polarization, and stable phase center was used. Due to its good radiation characteristics and small form-factor, this antenna was selected to study the respiratory rates of ten test subjects. The results were compared with a standard respiratory-rate measurement using a respiration belt transducer. The measurement results using the proposed and the standard systems showed excellent agreement. The mean error value of the respiratory rate measurements was 0.03 Hz with a statistical standard deviation of 0.03 Hz.

All-optical and broadband microwave fundamental/sub-harmonic I/Q down-converters.

Microwave I/Q down-converters are frequently used in image-reject super heterodyne receivers, zero intermediate frequency (zero-IF) receivers, and phase/frequency discriminators. However, due to the electronic bottleneck, conventional microwave I/Q mixers face a serious bandwidth limitation, I/Q imbalance, and even-order distortion. In this paper, photonic microwave fundamental and sub-harmonic I/Q down-converters are presented using a polarization division multiplexing dual-parallel Mach-Zehnder modulator (PDM-DPMZM). Thanks to all-optical manipulation, the proposed system features an ultra-wide operating band (7-40 GHz in the fundamental I/Q down-converter, and 10-40 GHz in the sub-harmonic I/Q down-converter) and an excellent I/Q balance (maximum 0.7 dB power imbalance and 1 degree phase imbalance). The conversion gain, noise figure (NF), even-order distortion, and spurious free dynamic range (SFDR) are also improved by LO power optimization and balanced detection. Using the proposed system, a high image rejection ratio is demonstrated for a super heterodyne receiver, and good EVMs over a wide RF power range is demonstrated for a zero-IF receiver. The proposed broadband photonic microwave fundamental and sub-harmonic I/Q down-converters may find potential applications in multi-band satellite, ultra-wideband radar and frequency-agile electronic warfare systems.

Equivalent-Time Direct-Sampling Impulse-Radio Radar With Rotatable Cyclic Vernier Digital-to-Time Converter for Wireless Sensor Network Localization

This paper presents a rotatable cyclic Vernier digital-to-time converter (DTC) with 1.8 ps timing resolution on an 80 ns time scale. The proposed DTC features high timing resolution, and can be utilized in beam-steering arrays, which is infeasible for ordinary Vernier DTCs. The proposed DTC was implemented within a passive time-equivalent direct-sampling ultra-wideband impulse-radio radar system and was fabricated in 65 nm CMOS technology. This radar system is capable of quantizing direct-sampled impulse waveforms to provide full degrees of freedom for backend digital signal processing. The measured differential nonlinearity/integral nonlinearity of the DTC was +4.6/−3 and 12.4/−9.4 where the LSB was 1.8 ps, and the total power consumption was 133 mW. Also, a new method for localization between wireless sensor nodes of equivalent-time direct-sampling radar is presented in this paper; this method can theoretically achieve resolution as high as that of regular radar.

Metal-Cased Oil Well Inspection Using Near-Field UWB Radar Imaging

In this paper, monitoring of metal-cased oil wells using the ultrawideband (UWB) radar is proposed. The inspection includes the detection and imaging of perforations and corroded areas in a metal pipe. Detection of small anomalies/ perforations on the surface of a narrow metal pipe is very challenging. Here, we present a method for imaging such small anomalies based on the extra time delay of the reflected pulse due to the effect of perforation in the radar near field. In this paper, the necessary concepts for the use of UWB radar specified for this application are developed and proved based on different measurement and simulation scenarios. We have experimentally demonstrated the effect of the perforations’ size on the time delay of reflected pulses. The distance between the perforation and the radar, for the near-field phenomenon, is critical for an effective detection and imaging. Therefore, we also studied the optimal distance between the radar and the perforation. Perforations with a size range of 1–3 cm are considered for the experiments and simulations. The experiments are done both in air and diesel. Synthetic aperture radar processing is used to reconstruct the images of the perforations and corroded area. Measurement and simulation results demonstrate the potential of UWB radar systems for oil well monitoring applications.

Optimization of the Working Conditions for Magnetic Nanoparticle-Enhanced Microwave Diagnostics of Breast Cancer.

Magnetic nanoparticle-aided microwave imaging is recently gaining an increasing interest as a potential tool for breast cancer diagnostics. This is due to the peculiar features of magnetic nanoparticles, which are biocompatible, can be selectively targeted to the tumor, and may change their microwave magnetic response when modulated by a polarizing magnetic field. This latter aspect is particularly appealing, as it enables the physical separation of the microwave signal due the malignancy, targeted by the nanoparticles, from that due to healthy tissue. This increases the specificity of the diagnostic tool, in principle allowing a diagnosis based solely on the detection of the signal due to the nanoparticles response. In this respect, a proper choice of the polarizing field modulation can remarkably increase the detection performances. This paper deals with this issue, by providing the mathematical framework for such an optimization and a procedure for estimating the required quantities from a set of proper measurements. The procedure is then experimentally demonstrated by applying it to a recently developed ultrawideband radar system for the magnetic nanoparticle-aided detection of breast cancer. For such a system, the optimal magnetic field modulation is determined.

Phase-Coded Stepped Frequency Linear Frequency Modulated Waveform Synthesis Technique for Low Altitude Ultra-Wideband Synthetic Aperture Radar

This paper discusses a new waveform synthesis technique particularly suitable for low altitude ultra-wideband (UWB) synthetic aperture radar (SAR) systems. The proposed technique synthesizes a phase-coded UWB chirp by transmitting a burst of coherent phase-coded sub-band chirp pulses and combining the collected echoes using a special digital signal processing (DSP) algorithm. A lab prototype is built for the feasibility study and validation of the proposed technique. From the results, it is clearly shown that 1) the proposed technique can synthesize UWB chirp pulses; 2) the proposed DSP algorithm can combine the collected sub-band echoes into an echo of a wider bandwidth; and 3) the proposed technique can improve the range resolution of the SAR system without altering much of its system design. The main advantage of the proposed technique is that it can improve the range resolution of an existing SAR system without the need to increase the baseband bandwidth of the system.

Through-Wall Multiple Targets Vital Signs Tracking Based on VMD Algorithm.

Targets located at the same distance are easily neglected in most through-wall multiple targets detecting applications which use the single-input single-output (SISO) ultra-wideband (UWB) radar system. In this paper, a novel multiple targets vital signs tracking algorithm for through-wall detection using SISO UWB radar has been proposed. Taking advantage of the high-resolution decomposition of the Variational Mode Decomposition (VMD) based algorithm, the respiration signals of different targets can be decomposed into different sub-signals, and then, we can track the time-varying respiration signals accurately when human targets located in the same distance. Intensive evaluation has been conducted to show the effectiveness of our scheme with a 0.15 m thick concrete brick wall. Constant, piecewise-constant and time-varying vital signs could be separated and tracked successfully with the proposed VMD based algorithm for two targets, even up to three targets. For the multiple targets’ vital signs tracking issues like urban search and rescue missions, our algorithm has superior capability in most detection applications.

A Novel Picosecond Pulse Generation Circuit Based on SRD and NLTL.

Because of the importance of ultra-wideband (UWB) radar in various applications, short pulse generation in UWB systems has attracted a lot of attention in recent years. In order to shorten the pulse, nonlinear transmission line (NLTL) is imported, which expands the application of step recovery diode (SRD) for pulse generation. Detailed analysis and equations for this SRD and NLTL-based pulse generation are provided and verified by simulation and experimental results. Factors that could cause pulse waveform distortions are also analyzed. The generator circuit presented in this paper generates 130ps and 3.3V pulse, which can be used in UWB radar systems that require sub-nanosecond pulses.

Multi-Human Detection Algorithm Based on an Impulse Radio Ultra-Wideband Radar System

In this paper, we propose a multi-human detection algorithm based on impulse radio ultra-wideband radar system. With our proposed algorithm, the multi-human detection can be performed by repeatedly performing clustering and detecting processes. More specifically, the system detects an effective peak of the first single cluster which is composed of peaks adjacent to each other and then repeat this process until effective peaks of clusters caused by multiple people are successfully detected sequentially. As our performance metrics, we take into account the performance analysis in terms of the error probability based on the results of the statistical analysis. More specifically, we first cross-verify that the empirical result theoretically follows the Log-normal distribution by comparing the theoretical and empirical results obtained through laboratory experiments. Then, we statistically analyze the received signals under the Log-normal distribution assumption. After that, this statistical result is adopted to the performance analysis of the error probability in terms of the total error probability. Note that the performance of our proposed algorithm is affected by the threshold value. Based on it, the optimal threshold is analyzed and we provide the sample guidelines for optimally adjusting the threshold value under given various environment factors. Finally, some selected experimental results are presented to show the validity of our proposed algorithm by comparing the performance between the proposed algorithm and the conventional algorithm.

An Adaptive-MSSA-Based Algorithm for Detection of Trapped Victims Using UWB Radar

Postdisaster search and rescue is an important application of ultrawideband (UWB) radar systems, which mainly detect trapped victims by their respiratory-motion response. The development of a respiratory-motion detection (RMD) algorithm that can eliminate nonstationary clutter and noise is a challenging task for the application. A new algorithm is proposed to deal with the task in this letter. It uses the multichannel singular spectrum analysis (MSSA) technique to reconstruct the respiratory-motion response detected by a UWB radar. During the reconstruction, the periodicity and range interrelation characteristics of the response are exploited to adaptively identify signal subspaces. The performance of the algorithm is verified both by simulated and real data. The results show its improved performance over the reference algorithms, e.g., a singular-value-decomposition-based algorithm. The adaptive-MSSA-based RMD algorithm has great promise not only in practical use but also for future research of UWB-radar-based human being remote sensing.

Impact analysis of LTCC materials on microstrip filters’ behaviour up to 13 GHz

Purpose – The purpose of this paper is to consider the adequacy of various microstrip filters’ behaviour based on different low-temperature co-fired ceramic (LTCC) dielectrics in the high frequency (HF) area up to 13 GHz. Design/methodology/approach – Low pass, band pass and band stop filters for ultra-wideband radar systems were designed, simulated, fabricated and measured using three various dielectric substrates: Dupont GreenTape 951, Dupont GreenTape 9K7 and Murata LFC. Findings – It is not possible to unambiguously determine the most suitable LTCC dielectric for these filter design because, in general, all designed filters fulfilled requirements (attenuation, cut off frequencies) with minimal divergences, but temperature-stable dielectric and physical properties of Murata LFC make them a promising ceramic for HF application (repeatability of realised experiments). Originality/value – The novelty of this work lies in unconventional usage of LTCC as material with defined dielectric properties proper for HF applications.

Complex Radar Cross Section Measurements of the Human Body for Breath-Activity Monitoring Applications

An experimental setup for complex mono-static radar cross section (RCS) measurements in the 1–10-GHz-frequency band, employing a suitably modified semianechoic chamber, is presented and characterized. The foreseen application is the measurement of the complex RCS of the human body during respiratory activity, to ease the design and optimization of ultrawideband (UWB) radar systems for breath-activity monitoring. The proposed RCS test range is calibrated by means of a readily available aluminum flat panel and its performance is tested against canonical targets, evaluating uncertainty in magnitude, and phase measurements. The setup is then employed to carry out investigations on the complex RCS of a volunteer, focusing on its changes resulting from breath activity. Applying the measured RCS patterns to a specifically developed model, the feasibility of the UWB radar approach for achieving a continuous contact-less monitoring of breath activity in a subject at rest is clearly demonstrated. Finally, experimental tests of the application of the proposed radar technique to real-world scenarios are shown, and the safety of RCS measurements and UWB radar monitoring, with reference to exposure of the monitored subject to the radiated electromagnetic fields, is evaluated.

순차적 샘플링 방식을 이용한 가상 잡음 레이더 개념 증명

초 광대역 레이더는 숨겨진 물체를 찾는데 많은 장점을 가지고 있기 때문에, 지표 투과 레이더나 수풀 투과 레이더와 같은 투과레이더에 널리 이용되고 있다. 초 광대역 레이더의 종류 중에 하나인 잡음 레이더는 간섭 환경에 강한 특성을 가지고 있다. 그러나 일반적인 잡음레이더는 고속의 아날로그 디지털 변환기가 필요하여 광대역 레이더로 제작하는데 어려움이 있다. 본 논문에서는 간섭에 강한 특징을 가지면서 고속의 아날로그 디지털 변환기가 필요하지 않은 가상 잡음 레이더 시스템이 연구되었다. 또한, 초 광대역 시스템이 저주파에서 구현되었고, 이는 실험으로 성능이 검증되었으며, 제안된 가상잡음 레이더 시스템의 개념도 증명되었다. Ultra-wideband(UWB) radar is widely used in many penetration radar applications, such as ground-penetrating radar and foliage-penetrating radar, because it has many advantages in detecting concealed objects. One type of UWB radar system is random noise radar, which many be robust to jamming environment. However conventional random noise radar requires high-speed analog-to-digital convertor(ADC) for matched filtering. In this thesis, a pseudo-random noise radar system that maintains anti-jamming characteristics but does not require high-speed ADC is researched. and The UWB system is implemented in a low frequency system, and its performance has been demonstrated by experiment, which proves the concept of the proposed pseudo-random noise radar system.

Microwave radiation imaging using inverse synthetic aperture radar technique

Double-ridged horn antennas were used in ultra wideband radar system to create microwave radiation images. The images were obtained using inverse synthetic aperture radar technique. Transfer function of the calibrated radar system was close to one up to 22 GHz. High quality images of metallic and organic objects were created due to unique characteristic of ultra wideband radiated pulse. Metallic objects covered by visually opaque obstacles became detectable. The components of measurement set-up and the data processing are both important for the formation of these images. The obtained results confirmed the ability of ultra wideband radar to form images for various practical applications including security systems. Higher frequency of such radar system can be raised up to 40 GHz-50 GHz.DOI: http://dx.doi.org/10.5755/j01.eee.21.1.5389

Accurate heartbeat monitoring using ultra-wideband radar

We demonstrate an accurate remote measurement of heartbeats using an ultra-wideband radar system. Although most conventional systems use either continuous waves or impulse-radio systems for remote vital monitoring, continuous waves suffer from non-stationary clutters, while impulse-radio systems cannot detect heartbeats. Our ultra-wideband radar system has a moderate fractional bandwidth intermediate of these systems, resulting in both the suppression of clutters and high sensitivity in measuring accurate heart rates even in a dynamic environment. A simultaneous measurement of the vital signal of a participant employing the ultra-wideband radar and electrocardiography reveals the high accuracy of the radar system in measuring the heart rate varying over time.

Dielectric Constant and Boundary Extraction Method for Double-Layered Dielectric Object for UWB Radars

Microwave ultra-wideband (UWB) radar systems are advantageous for their high-range resolution and ability to penetrate dielectric objects. Internal imaging of dielectric objects by UWB radar is a promising nondestructive method of testing aging roads and bridges and a noninvasive technique for human body examination. For these applications, we have already developed an accurate internal imaging approach based on the range points migration (RPM) method, combined with a method that efficiently estimates the dielectric constant. Although this approach accurately extracts the internal boundary, it is applicable only to highly conductive targets immersed in homogeneous dielectric media. It is not suitable for multi-layered dielectric structures such as human tissues or concrete objects. To remedy this limitation, we here propose a novel dielectric constant and boundary extraction method for double-layered materials. This new approach, which simply extends the Envelope method to boundary extraction of the inner layer, is evaluated in finite difference time domain (FDTD)-based simulations and laboratory experiments, assuming a double-layered concrete cylinder. These tests demonstrate that our proposed method accurately and simultaneously estimates the dielectric constants of both media and the layer boundaries.