Ultra-wide Band Pulse Radar Research Articles

Classification of human body motions using an ultra-wideband pulse radar.

BACKGROUND: The motion or gestures of a person are primarily recognized by detecting a specific object and the change in its position from image information obtained via an image sensor. However, the use of such systems is limited due to privacy concerns.OBJECTIVE: To overcome these concerns, this study proposes a radar-based motion recognition method.METHODS: Detailed human body movement data were generated using ultra-wideband (UWB) radar pulses, which provide precise spatial resolution. The pulses reflected from the body were stacked to reveal the body’s movements and these movements were expressed in detail in the micro-range components. The collected radar data with emphasized micro-ranges were converted into an image. Convolutional neural networks (CNN) trained on radar images for various motions were used to classify specific motions. Instead of training the CNNs from scratch, transfer learning is performed by importing pretrained CNNs and fine-tuning their parameters with the radar images. Three pretrained CNNs, Resnet18, Resnet101, and Inception-Resnet-V2, were retrained under various training conditions and their performance was experimentally verified.RESULTS: As a result of various experiments, we conclude that detailed motions of subjects can be accurately classified by utilizing CNNs that were retrained with images obtained from the UWB pulse radar.

Ultra-Wideband Pulse Radar Mounted on an Unmanned Aerial Vehicle for the Monitoring of Moving Objects

Ultra-Wideband Pulse Radar Mounted on an Unmanned Aerial Vehicle for the Monitoring of Moving Objects

Ultra-Wideband Pulse Radar with Discrete Stroboscopic Receiver for Detection of Small Targets Behind Dielectric Obstacles

Abstract Increasing requirements in the field of security, in particular in the transport sector, the rescue work, the inviolability of private property and others urged to research work in the field of radar monitoring people, vehicles or other objects in the environment that not allow make so using the most popular and available technology for production and analysis of video images. These conditions of poor visibility, or even lack thereof, are darkness, bad weather, smoke, dust, wall (roof) buildings and the vehicle body. Existing instruments and special equipment occupy a certain niche in this area, mainly for counter-terrorism operations. However, such equipment is not readily available and extremely high price. In the paper presented research is development of the group’s existing radar technology in the field of location through opaque obstacles.

Design and Implementation of an Embedded Cardiorespiratory Monitoring System for Wheelchair Users

A novel design of an embedded cardiorespiratory monitoring system for wheelchair users is proposed. The entire system is composed of a sensor node, a smartphone, and a cloud server. The sensor node contains two parts of an ultra-wideband pulse radar and the data processing module; the former is used to obtain continuous vital-sign signals, and the latter processes the sampled signals to estimate the heart rate and the respiration rate, implemented in an embedded system to achieve a fully integrated radar system. The smartphone functions as the data bridge between the sensor node and the cloud server, which is responsible for sending emergent messages. Experiment results show that the proposed system could work reliably in static and dynamic cases of wheelchairs.

Calibrated Layer-Stripping Technique for Level and Permittivity Measurement With UWB Radar in Metallic Tanks

A method to measure liquid level and electrical properties based on ultra-wideband pulsed radar is developed in this paper. Current methods of material property measurement using free-space radar typically use computationally intensive frequency-domain analysis or finite time-domain methods. The method presented is modified from layer-stripping algorithms and includes several improvements over previous techniques, such as an antenna array that allows measurement in a metallic tank environment and a method of calibration that characterizes path-loss and near-field effects for accurate amplitude-distance prediction. The method presented here also estimates the material loss properties and uses accumulated power with noise compensation to predict reflected pulse power. The method extends the use of pulsed radar for liquid-level measurement in tanks to the evaluation of liquid permittivity and the estimation of liquid height in liquids consisting of multiple layers. The accuracy of the presented method is evaluated using a transmitting single antenna element, a four-element antenna array, and an eight-element antenna array for measurement in a metallic tank environment. Accuracy is improved with larger antenna arrays, but the calibration becomes more critical. The accuracy for varying layer heights and materials is investigated to demonstrate the method reliability.

A K-Band Reconfigurable Pulse-Compression Automotive Radar Transmitter in 90-nm CMOS

A K-band ultra-wideband (UWB) pulse-compression (PC) automotive radar transmitter in 90-nm CMOS is presented, which is composed of the fully integrated pulse generator, mixer, driver amplifier, phase-locked loop, and timing circuitry. The PC technique with coding gain can effectively enhance the detection resolution and also improve the signal-to-noise ratio (SNR). We propose a PC transmitter allowing fast and precise code generation with small power consumption and chip area, and also offering reconfigurable capability. Compared with previously reported UWB pulse radars with relatively simple coding schemes, the proposed transmitter features a much more challenging 15-bit pseudonoise code design using high-speed shift registers, which can improve SNR up to 23.5 dB. The measured results demonstrate correct output waveforms corresponding to different modulation codes with the spectrum well confined under the regulation mask. With a modulation rate over 3 Gb/s (pulse repeat frequency of 6.125 MHz), a resolution of ~ 5 cm can be achieved.

Planar Differential Antenna Design and Integration With Pulse Radar Microchip Sensor

This paper reports the design and integration of a novel planar antenna on FR4 substrate with a system-on-a-chip ultra wideband pulse radar in 90-nm CMOS technology packaged in a 32 pin quad flat no-lead package, allowing the implementation of a short-range pulse radar sensor for biomedical applications. Functional tests have shown that the pulse radar sensor detects three targets with different areas (26 × 26, 13 × 26, and 13 × 13 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) for front-back movements up to 2 cm around a distance of 70 cm. Field operational tests show that the radar sensor allows the contactless detection of the respiratory rate of the persons under test, be they adult (both genders) and infant, for sub-centimeter chest movements up to a distance of 45 cm from the radar sensor.

From Tumor Targeting to Speech Monitoring: Accurate Respiratory Monitoring Using Medical Continuous-Wave Radar Sensors

Using microwaves to detect small physiological movements such as respiration and heartbeat dates back to the 1970s [1]. It is realized by detecting the phase information in the received radar signals, which is caused by Doppler shift due to the moving chest wall. The principle is similar to the radar guns used by police officers to detect over-speed vehicles. Based on the form of the transmit signal, there are basically two types of radars: continuous-wave (CW) radar and ultrawideband (UWB) radar. The CW radar falls into three subcategories: single-tone, stepped frequency (SFCW), and frequency-modulated CW (FMCW). Each category of radars has its specific advantages. The singletone CW radar has a simple system architecture that allows high-level chip integration [2]?[4]. It also has high accuracy (submillimeter) in relative displacement measurement [5]?[6]. Unfortunately, because no instant bandwidth is transmitted, single-tone CW radars do not carry range (i.e., absolute distance between the radar and the subject) information. FMCW radars are able to detect range information [7]?[8] but normally require a very large bandwidth and more sophisticated signal processing to realize high-accuracy relative displacement measurement. Researchers also have successfully integrated the FMCW radar on silicon chips [9]?[11]. SFCW radars carry some advantages of both singletone CW radars and FMCW radars and thus have been successfully used in applications such as fall detection [23]. In addition, a hybrid radar system combining the advantages of the single-tone and FMCW radars was reported in [12]. UWB biomedical radars have veryhigh-range resolution due to its wideband nature [13]. The state of the art shows that UWB pulse radars have been efficiently implemented on silicon [74] and have been successfully applied to the accurate detection of respiratory rate and apnea in adults and infants [75].

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.

Planar Differential Antenna for Short-Range UWB Pulse Radar Sensor

A novel planar differential ultrawideband (UWB) antenna was designed and implemented on low-cost FR4 substrate and characterized experimentally. The dedicated design was motivated by the implementation of a UWB pulse radar sensor obtained by co-integrating a system-on-a-chip UWB pulse radar packaged in QFN32 package with the proposed antenna, one for the transmitter and one for the receiver. The experimental results confirm the predictions obtained by simulations, and the effectiveness of the novel antenna design for the implementation of low-cost short-range pulse radar sensor was validated by field operational tests.

Accurate Image Expansion Method Using Range Points Based Ellipse Fitting for UWB Imaging Radar

Ultra-wideband (UWB) pulse radars have a definite advantage in high-range resolution imaging, and are suitable for short-range measurements, particularly at disaster sites or security scenes where optical sensors are rarely suitable because of dust or strong backlighting. Although we have already proposed an accurate imaging algorithm called Range Points Migration (RPM), its reconstructible area is too small to identify the shape of an object if it is far from the radar and the size of the aperture is inadequate. To resolve this problem, this paper proposes a novel image expansion method based on ellipse extrapolation; it enhances extrapolation accuracy by deriving direct estimates of the observed range points distributed in the data space. Numerical validation shows that the proposed method accurately extrapolates part of the target boundary, even if an extremely small region of the target boundary is obtained by RPM. key words: UWB pulse radars, range points migration, ellipse fitting, image expansion

光载超宽带脉冲雷达信号传输性能研究

Monocycle pulse and doublet pulse used for ultra-wideband(UWB) pulse radar are generated with dual-parallel Mach-Zehnder modulator(DPMZM).Based on the fadio over fiber(RoF) technology,the transmission performance of the UWB pluses over standard single mode fiber(SSMF) are theoretically analyzed.It is found that monocycle pulse is broadened with the increase of transmission distance,while doublet pulse is firstly compressed and then broadened.Monocycle pulse and doublet pulse with different width satisfying the FCC requirements of UWB pulse radar can be obtained,when the accumulated dispersion of the radar signal is compensated in different degree with dispersion compensation fiber(DCF) after 100 km transmission over SSMF.

Accurate and Omnidirectional UWB Radar Imaging Algorithm With RPM Method Extended to Curvilinear Scanning Model

Ultrawideband pulse radars are a promising technology for high-quality imaging sensors for rescue robots in the near field because they have the advantage of high range resolution. We have already proposed the accurate and fast imaging algorithm as range point migration (RPM), which employs the direction of arrival (DOA) with the global characteristic of the multiple observed ranges. However, this algorithm assumes the line scanning of an omnidirectional antenna and limits the imaging range. To overcome this limitation, this letter derives an extended RPM method, which accomplishes omnidirectional imaging and accurate target positioning. As a false-image-reduction scheme in this method, this letter introduces a postprocessing algorithm, which constrains the searching range for DOA estimation by using the initial RPM image. The results of numerical simulations, including noisy situations, show that the proposed method accomplishes accurate and omnidirectional imaging on the order of 1/100 wavelength and enhances the imaging range while avoiding false images.

Extended Imaging Algorithm Based on Aperture Synthesis With Double-Scattered Waves for UWB Radars

Ultrawideband (UWB) pulse radar with high range resolution is suitable for near-field sensing. Applications of UWB pulse radar include human body identification in blurry vision for security or rescue purposes and accurate spatial measurements for industrial products such as a reflector antenna. The synthetic aperture radar is still promising for these applications because it creates an accurate image even for near-field targets in free space. However, for complex-shaped or multiple objects, this algorithm suffers from increased shadow region because it employs only a single-scattered signal for imaging. To resolve this difficulty, this paper proposes a novel imaging algorithm based on aperture synthesis for double-scattered signals. In general, double-scattered waves include independent information on target points, which are not obtained by a single-scattered wave. Based on this principle, the proposed method effectively synthesizes the double-scattered signals and enhances the reconstructible range of a target shape, part of which becomes a shadow in the former approach. In order to enhance accuracy, a false image suppression approach based on the Fresnel zone theory is also incorporated in the proposed method. The results from numerical simulations and an experiment verify that our method significantly enhances the visible range of target surfaces without either a priori knowledge of target shapes or preliminary observation of their surroundings.

An Imaging Algorithm of a Target with Arbitrary Motion for Ultra Wide-Band Radar with a Small Number of Antennas

UWB (ultra wide-band) pulse radar is a promising candidate for surveillance systems. The fast SEABED (Shape Estimation Algorithm based on BST and Extraction of Directly scattered waves) imaging algorithm is deployed in the application of UWB pulse radar in fields that require real-time operations. However, since the SEABED algorithm uses signals received at multiple locations, this method either needs to scan antennas or to install many antennas. Such systems are inevitably costly and unrealistic for applications such as surveillance. To overcome this problem, a revised SEABED algorithm that estimates unknown target shape based on target motion using only a pair of fixed antennas was developed. However, the method cannot be used when the target moves arbitrarily because it assumes the target motion is parallel to the baseline of the pair of antennas. In this paper, we propose a new UWB radar imaging algorithm that is applicable even for targets with arbitrary motion. The proposed method introduces another antenna which is added to the pair of antennas used in the revised SEABED, and estimates unknown target motion based on the target surface using the three antennas. Next, the proposed method applies the SEABED imaging algorithm to the estimated motion and obtains the target image. Some numerical simulations establishes that the proposed method can accurately estimate the target shape even under severe conditions.

2-Dimensional Accurate Imaging with UWB Radar Using Indoor Multipath Echoes for a Target in Shadow Regions

UWB (Ultra Wide-Band) pulse radar is promising for surveillance systems because it has an outstanding high range-resolution. To realize an accurate UWB radar imaging system, we propose a new approach that employs multipath echoes from a target in an indoor environment. Using multipath echoes, the proposed system can accurately estimate images, even for targets in a shadow region where the targets are out of sight of the antenna. We apply a simple interferometry technique using the multiple mirror image antennas generated by multipath propagation. We find that this simple method also produces many undesired false image points. To tackle this issue, we also propose an effective false image reduction algorithm to obtain a clear image. Numerical simulations verify that most of the false image points are removed and the target shape is accurately estimated.

Accurate UWB Radar Three-Dimensional Imaging Algorithm for a Complex Boundary Without Range Point Connections

Ultrawide-band pulse radars have immeasurable potential for a high-range-resolution imaging in the near field and can be used for noncontact measurement of industrial products with specular or precision surfaces, such as reflector antenna or aircraft fuselage, or identifying and locating the human body in security systems. In our previous work, we developed a stable and high-speed 3-D imaging algorithm, Envelope, which is based on the principle that a target boundary can be expressed as inner or outer envelopes of spheres, which are determined using antenna location and observed ranges. Although Envelope produces a high-resolution image for a simple shape target that may include edges, it requires an exact connection for observed ranges to maintain the imaging quality. For complex shapes or multiple targets, this connection becomes a difficult task because each antenna receives multiple echoes from many scattering points on the target surface. This paper proposes a novel imaging algorithm without range point connection to accomplish high-quality and flexible 3-D imaging for various target shapes. The algorithm uses an accurate estimation for the direction of arrival using signal amplitudes and realizes direct mapping from observed ranges to target points. Several comparative studies of conventional algorithms clarify that our proposed method accomplishes accurate and reliable 3-D imaging even for complex or multiple boundaries.

가변 커버리지를 갖는 위성 관제용 접이식 헬리콘 반사체 안테나 성능 연구

헬릭스 안테나는 관제, 관측, 탐사, 통신 위성 등에서 관제(TT&C), 데이터 통신, GPS 수신 시스템, 전술 시스템으로 활용되고 있다 위성의 Z축에서 최대 지향성과 방사 특성을 갖는 헬릭스는 광대역의 임피던스와 통신 커버리지 대역을 제공할 수 있다. 도파관 혼 구조는 흔히 레이다 분야에 이용되는데, 지반 탐사 레이다 및 전자파 장애 측정 등 초 광대역 펄스를 필요로 하는 곳에 사용된다. 또한 크기가 비교적 작고, 적은 방사 왜곡으로 인한 고효율과 낮은 반사 특성을 갖는 장점이 있다. 본 논문에서는 고용량의 데이터를 전송하여 넓은 주파수 대역폭을 사용하는 통신 및 원격 탐사 위성에 적합한 도파관 혼-헬릭스 결합 안테나를 설계한다. 설계된 변형 구조 안테나는 S 밴드에서 가변 빔 스캐닝 모드를 갖는 혼-헬릭스 결합 헬리콘 구조로 관제, 탐사, 고속 데이터 통신용 등의 다기능 안테나로 동작한다. 도파관 혼은 테이퍼된 헬릭스를 감싸는 접이식 반사체로 설계하여 구조물의 소형화를 유도한다. 현재 개발 중인 차세대 다목적 실용위성에서는 고성능의 탑재체를 활용하기 때문에 정밀하고 안정된 위성 자세 제어 능력을 요구하고, 위성 안테나의 지향성 요구 조건이 강화된다. 이를 위해 설계된 안테나의 위성 초기 배치에 따른 링크 분석을 통해 위성체의 자세 및 운용 모드에 따라 다른 결과를 갖는 빔 스캐닝을 산출하고 각 모드에서의 자료 전송률에 대해 연구한다. Helix antennas have been widely applied to satellite TT&C, data communication and GPS receiver systems onboard military, remote sensing and communication purpose satellites. The helix antennas are known to be convenient to control impedance and radiation coverage characteristics with a maximum directivity in satellite z-axis. Waveguide horn is commonly used for radar system that needs ultra-wideband pulse for exploration ground radar and electromagnetic disability measurement etc. It has high efficiency and low reflection characteristics provided by the low-profile shape and suppressed radiation distortion. In this paper, a waveguide horn structure incorporated with helix antenna design is proposed for satellite applications that require ultra-wideband pulse radar and high rate RF data communication link to ground station over wide coverage area. The main design concern is to synthesize variable beam forming pattern based on modified horn-helix combination helicone structure such that multi-mission antenna is implemented applicable for TT&C, earth observation, high data rate transmission. Waveguide horn helps to reduce the overall antenna structure size by introduction fold type reflector connected to the tapered helix antenna. The next generation KOMPSAT satellite currently under development requires high-performance precision attitude control system. We present an initial design of a hybrid hern-helix antenna structure suitable for efficient RF communication module design of multi-purpose satellite systems.

Code-Division Multiple Transmission for High-Speed UWB Radar Imaging With an Antenna Array

The ultrawideband (UWB) radar is a promising high-resolution 3-D imaging technique for near targets. We have developed a high-speed imaging algorithm, SEABED, for a UWB pulse radar, a key real-time imaging technology. When the algorithm is applied to UWB, antenna scanning for data acquisition takes significantly longer than calculating the SEABED algorithm itself. This presents a serious problem for the real-time application of UWB radar. In this paper, we use pseudonoise (PN) sequences as the transmitting waveforms, while the original work on the SEABED algorithm assumed impulsive short-wave pulses. Using PN sequences enables us to simultaneously transmit signals with multiple antennas, eliminating the need to scan antennas. We demonstrate that the proposed radar system works well using random sequences to suppress direct waves, which is critical in achieving high speeds for imaging.

Experimental Study of Shadow Region Imaging Algorithm with Multiple Scattered Waves for UWB Radars

Ultra-wide band (UWB) radar is capable of high range resolution near fleld sensing, and is thus applicable to security systems designed to identify a human body even when invisible. Although Synthetic Aperture Radar (SAR) creates a stable and accurate target image for such applications, it often sufiers from increased shadow regions in the case of complex or multiple targets. On the contrary, a multiple scattered wave has the potential to enlarge a visible range on target surfaces because it propagates a path which difiers from that of a single scattered wave. While various algorithms based on time-reversal processing with multiple scattered waves have been developed, these require a priori information of the surroundings or a target model. This paper proposes a shadow region imaging algorithm based on the aperture synthesis of multiple scattered waves. While the proposed algorithm only synthesizes a double scattered wave according to its propagation path, it can directly increase the visible area and is applicable to arbitrary target shapes. The results from the numerical simulation and experiment verify that the proposed algorithm directly makes a shadow region visible without a preliminary observation. 1. INTRODUCTION UWB pulse radar is promising as a near fleld sensing technique with high range resolution, and is applicable to non-contact measurement of re∞ector antennae or aircraft bodies that have precise and specular surfaces. It is also applicable to a collision avoidance for automobile under the low visibility. For such applications, various imaging algorithms have been published, as the SEABED accomplishes real-time imaging by using a reversible transform BST (1), and the Envelope+SOC reconstructs the target surface to an accuracy on the order of 1/100 wavelength (2). The SAR algorithm remains promising, in providing a stable and accurate image by using the full information of the received signals (3). However, in the case of complex or multiple targets, any of the algorithms sufiers from increased shadow regions because they use only the single scattered wave for imaging. On the contrary, except for an edge difiraction wave, a multiple scattered wave passes through a path, difierent from that of a single scattered wave, which means that the multiple scattered echo has the potential to enhance the visible range. Although the time reversal algorithms with multiple scattered waves have been proposed when focusing on reliable target detection or accurate positioning in cluttered situations (4{6), they require target modeling or a priori information of the surrounding environment like the walls. To expand the applicability of these methods, this paper proposes a non-parametric imaging algorithm based on the aperture synthesis of multiple scattered signals. The results obtained from numerical simulations and an experiment verify the efiectiveness of the proposed method which is applicable to arbitrary target shapes, and directly enlarges the visible range of the target surface. 2. CONVENTIONAL ALGORITHM Figure 1 shows the system model. It assumes that the target has an arbitrary shape with a clear boundary, and high conductivity like metallic objects. The propagation speed of the radio wave c is assumed to be a known constant. A mono-cycle pulse is used as the transmitting current, and the space is normalized by ‚ as the center wavelength of the pulse. The omni-directional antenna is scanned in the plane z = 0. The real space in which the target and antenna are located is expressed by the parameter r = (x;y;z). z > 0 is assumed for simplicity. s(X;Y;Z) is deflned as the output of the Wiener fllter at the antenna location at (x;y;z) = (X;Y;0), where Z = ct=(2‚) is expressed as a function of the time t. As a spatial measurement in the near fleld, the SAR algorithm has an ability to create a stable and accurate image by using the UWB signal. The distribution image I1(r) obtained by the SAR is formulated as