Ultra-wideband Radar Applications Research Articles

Performance enhancement of Vivaldi-shaped planar UWB antenna using a single-layer FSS reflector

This work proposes the design of a frequency-selective surface (FSS)-based planar monopole antenna for ultra-wideband (UWB) communication applications. The UWB response is observed by integrating a Vivaldi-shaped slot and by introducing a stepped-like pattern on the bottom edges of the radiating patch, while the back side is composed of a partial ground plane. This configuration results in a broad impedance bandwidth spanning from 3.11 to 20 GHz. For radiation performance enhancement of the proposed antenna, a single-layer UWB FSS reflector is placed beneath the antenna element at an optimized distance. The proposed FSS reflector employs a 3 × 3 array of fractal structure with a unit cell size of 12.25 × 12.25 mm2. The designed FSS reflector exhibits a linear phase response over a frequency range of 3.28 to 14 GHz, with a stop-band transmission coefficient less than -10 dB. The incorporation of the FSS reflector results in an increased gain, elevating it from 1 to 4 dBi at low-band frequencies, while at mid-band frequencies, the gain is increased from 1 to 6 dBi. The structural configuration of the proposed antenna yields directional far-field patterns, making it well-suited for UWB radar applications.

Non-Contact Breathing Monitoring Using Sleep Breathing Detection Algorithm (SBDA) Based on UWB Radar Sensors.

Ultra-wideband radar application for sleep breathing monitoring is hampered by the difficulty of obtaining breathing signals for non-stationary subjects. This occurs due to imprecise signal clutter removal and poor body movement removal algorithms for extracting accurate breathing signals. Therefore, this paper proposed a Sleep Breathing Detection Algorithm (SBDA) to address this challenge. First, SBDA introduces the combination of variance feature with Discrete Wavelet Transform (DWT) to tackle the issue of clutter signals. This method used Daubechies wavelets with five levels of decomposition to satisfy the signal-to-noise ratio in the signal. Second, SBDA implements a curve fit based sinusoidal pattern algorithm for detecting periodic motion. The measurement was taken by comparing the R-square value to differentiate between chest and body movements. Last but not least, SBDA applied the Ensemble Empirical Mode Decomposition (EEMD) method for extracting breathing signals before transforming the signal to the frequency domain using Fast Fourier Transform (FFT) to obtain breathing rate. The analysis was conducted on 15 subjects with normal and abnormal ratings for sleep monitoring. All results were compared with two existing methods obtained from previous literature with Polysomnography (PSG) devices. The result found that SBDA effectively monitors breathing using IR-UWB as it has the lowest average percentage error with only 6.12% compared to the other two existing methods from past research implemented in this dataset.

Radar-based microwave breast cancer detection system with a high-performance ultrawide band antipodal Vivaldi antenna

In this study, a novel ultrawide band (UWB) antipodal Vivaldi antenna with three pairs of slots was designed to be used as a sensor in microwave imaging systems for breast cancer detection. The proposed antenna operates in UWB frequency range of 3.05-12.2 GHz. FR4 was used as a dielectric material and as a substrate for forming the antenna that has a compact size of 36 mm x 36 mm x 1.6 mm. Frequency and time domain performance of the proposed antenna have been investigated and results show that it meets the requirements for UWB radar applications with linear phase response, nearly constant group delay, ultrawide bandwidth, and directional properties at most of the operating frequency. Then, the capacity of the proposed antenna as a sensor was tested in a monostatic microwave breast imaging system that was developed in the CST Microwave Studio (CST MWS) simulation software. In the simulation application, 50 mm radius hemisphreical breast models with different densities were formed and 2 mm diameter spherical tumor was placed inside them. Antennas were positioned cylindrically around the breast to send Gaussian pulse and collect backscattered signals. After signal processing steps, tumors were screened at correct positions with high resolution. Finally, a monostatic radar-based breast phantom measurement system was developed to automatically scan the breast phantom in the prone position. To perform experimental measurements, an electrically and anatomically realistic homogeneous breast phantom with tumor inside was fabricated. Screening of the tumor at correct location indicates that the proposed antenna and the microwave imaging system developed using this antenna are suitable for the detection of breast cancer at the early stage.

The UWB Radar Application in the Aviation Security Systems

In the process of our research, we have identified new methods of processing ultra-wide-band (UWB) radar signals and possibilities of the UWB radar use in aviation security systems. We paid our main attention to finding new algorithms for tracking the movement of a person behind an obstacle using the UWB radar. Such UWB radar application is typical for tracking the movement of people behind obstacles in case of security forces intervention at an airport. In the research process, we used methods of analysis, synthesis, and measured data from the performed experiment. The main contribution of the paper is the development of new algorithms for locating the movement of a person behind an obstacle using a straight- line method in the case of using two independent UWB radar systems. The article did not examine the accuracy of determining the position of a person behind the obstacle. We found that when applying the Kalman filter after signal processing by the straight-line method, the trajectory of the person’s movement behind the obstacle was smoother. The results of processing the measurement signals of UWB radar by the linear method have shown that this method is applicable to tracking a person behind an obstacle and can be used in aviation security systems.

Reconfigurable dual notch band antenna on Si-substrate integrated with RF MEMS SP4T switch for GPS, 3G, 4G, bluetooth, UWB and close range radar applications

In this paper, a reconfigurable co-planner waveguide (CPW) fed circular shaped monopole ultra wide band (UWB) antenna with dual band notch characteristics based on silicon substrate is presented. The dual notch band characteristics are realized by inserting two slots, namely, U- and I-shaped, in the circular radiating patch to switch-off the WiMAX IEEE 802.16 (3.30–3.80 GHz) and WLAN IEEE 802.11a/h/j/n (5.15–5.35 GHz, 5.25–5.35 GHz, 5.47–5.725 GHz, 5.725–5.825 GHz) respectively. The reconfigurability from antenna is achieved by integrating the radio frequency micro-electro mechanical system based single pole four through (RF MEMS SP4T) switch in the U- and I-shaped slots of radiating patch. The measured results demonstrate the bandwidth of 0.68–16.23 GHz resulting in fractional bandwidth of 183.91%, and are well in accordance with the simulation results. The gain of proposed antenna varies from 2.58 to 5.05 dBi with radiation efficiency of 83–95% and exhibits the omnidirectional like pattern in H-plane and nearly dipole like pattern in the E-plane. Further, the performance of proposed antenna is analyzed by implementing an equivalent RLC resonant circuit model in both the frequency and time domain.

On the Design of Sinuous Antennas for UWB Radar Applications

Sinuous antennas are capable of producing ultrawideband (UWB) radiation with polarization diversity. This capability makes the sinuous antenna an attractive candidate for UWB polarimetric radar applications. Additionally, the ability of the sinuous antenna to be implemented as a planar structure makes it a good fit for close-in sensing applications such as ground penetrating radar. However, recent literature has shown the sinuous antenna to suffer from resonances, which degrade performance. Such resonances produce late time ringing, which is particularly troubling for pulsed close-in sensing applications. The resonances occur in two forms: log-periodic resonances on the arms, and a resonance due to the sharp ends left by the outer truncation. A detailed investigation as to the correlation between the log-periodic resonances and the sinuous antenna design parameters indicates the resonances may be mitigated by selecting appropriate design parameters. In addition, a novel truncation method is proposed to remove the sharp end resonance. Both simulation and measured results are provided to support the developed sinuous antenna design guidance.

Feature Extraction and Reconstruction by Using 2D-VMD Based on Carrier-Free UWB Radar Application in Human Motion Recognition.

As the size of the radar hardware platform becomes smaller and smaller, the cost becomes lower and lower. The application of indoor radar-based human motion recognition has become a reality, which can be realized in a low-cost device with simple architecture. Compared with narrow-band radar (such as continuous wave radar, etc.), the human motion echo signal of the carrier-free ultra-wideband (UWB) radar contains more abundant characteristic information of human motion, which is helpful for identifying different types of human motion. In this paper, a novel feature extraction method by two-dimensional variational mode decomposition (2D-VMD) algorithm is proposed. And it is used for extracting the primary features of human motion. The 2D-VMD algorithm is an adaptive non-recursive multiscale decomposition method for nonlinear and nonstationary signals. Firstly, the original 2D radar echo signals are decomposed by the 2D-VMD algorithm to capture several 2D intrinsic mode function (BIMFs) which represent different groups of central frequency components of a certain type of human motion. Secondly, original echo signals are reconstructed according to the several BIMFs, which not only have a certain inhibitory effect on the clutter in the echo signal, but can also further demonstrate that the BIMFs obtained by the 2D-VMD algorithm can represent the original 2D echo signal well. Finally, based on the measured ten different types of UWB radar human motion 2D echo analysis signals, the characteristics of these different types of human motion are extracted and the original echo signal are reconstructed. Then, the three indicators of the PCC, UQI, and PSNR between the original echo signals and extraction/reconstruction 2D signals are analyzed, which illustrate the effectiveness of 2D-VMD algorithm to extract feature of human motion 2D echo signals of the carrier-free UWB radar. Experimental results show that BIMFs by 2D-VMD algorithm can well represent the echo signal characteristics of this type of human motion, which is a very effective tool for human motion radar echo signal feature extraction.

The Broken-Heart Printed Antenna for Ultrawideband Applications: Design and Characteristics Analysis

A compact, slotted partial ground, broken-heart-shaped microstrip patch antenna intended for use in ultrawideband (UWB) applications is presented. The antenna is composed of a broken-heart-shaped patch and slotted partial ground plane. The antenna has an electrical dimension of 0.29l t 0.17l at the lowest operating frequency of 2.90 GHz. The finite element method (FEM)-based high-frequency structural simulator (HFSS) and the time-domain-method-based Computer Simulation Technology (CST) Microwave Studio simulator have been used to simulate the presented antenna. The antenna was measured after prototype fabrication. The antenna covers the bandwidth from 2.90 to 10.70 GHz. The maximum gain of the presented antenna is 5.3 dBi with a notable efficiency of 86.6%. The fidelity factor for faceto-face and side-by-side orientation of the antenna is ~79% and 80%, respectively. The impedance bandwidth of the presented antenna is wide enough to be used in UWB wireless communications as well as microwave imaging and UWB radar applications.

An Algorithm Based Wavelet Entropy for Shadowing Effect of Human Detection Using Ultra-Wideband Bio-Radar.

Ultra-wide band (UWB) radar for short-range human target detection is widely used to find and locate survivors in some rescue missions after a disaster. The results of the application of bistatic UWB radar for detecting multi-stationary human targets have shown that human targets close to the radar antennas are very often visible, while those farther from radar antennas are detected with less reliability. In this paper, on account of the significant difference of frequency content between the echo signal of the human target and that of noise in the shadowing region, an algorithm based on wavelet entropy is proposed to detect multiple targets. Our findings indicate that the entropy value of human targets was much lower than that of noise. Compared with the method of adaptive filtering and the energy spectrum, wavelet entropy can accurately detect the person farther from the radar antennas, and it can be employed as a useful tool in detecting multiple targets by bistatic UWB radar.

Design of Vivaldi Microstrip Antenna for Ultra-Wideband Radar Applications

The development of radar technology has an important role in several fields such as aviation, civil engineering, geology, and medicine. One of the essential components of the radar system is the antenna. The bandwidth can specify the resolution of the radar. The wider the bandwidth, the higher the resolution of radar. For Ground penetrating radar (GPR) or medical applications need with a high-resolution radar so it needs an antenna with a wide bandwidth. In addition, for the radar application is required antenna with directional radiation pattern. So, we need an antenna with wide bandwidth and directional radiation pattern. One of antenna that has meet with these characteristics is vivaldi antenna. In previous research, has designed several vivaldi microstrip antenna for ultra-wideband radar applications which has a working frequency of 3.1 to 10.7 GHz. However, these studies there is still a shortage of one of them is the radiation pattern from lowest to highest frequency radiation pattern is not uniform in the sense that not all directional. Besides the antenna material used is also not easily available and the price is not cheap. This paper will discuss the design of a vivaldi microstrip antenna which has a wide bandwidth with directional radiation pattern works on 3.1 to 10.7 GHz and using cheaper substrate. Substrates used for vivaldi microstrip antenna vivaldi is FR4 with a dielectric constant of 4.3 and a thickness of 1.6 mm. Based on the simulation results we obtained that the antenna design has frequency range 3.1-10.7 GHz for return loss less than -10 dB with a directional radiation pattern. This antenna gain is 4.8 to 8 dBi with the largest dimension is 50 mm x 40 mm.

Modification of Sinuous Antenna Arms for UWB Radar Applications

The sinuous antenna is modified to improve its performance for ultrawideband (UWB) radar applications. The radiated waveforms in the time domain of typical sinuous antennas contain a long ringing tail after the chirp-like main pulse when excited by a temporally short pulse. The ringing is due to resonances that are set up on the antenna arms and are essentially eliminated by modifying the shape of the arms. The first modification removes the sharp ends where the arms terminate, and the second changes the shape of the arms where they bend. These modifications are also shown to improve the gain flatness of the antennas. Three representative sinuous antennas are fabricated, tested, and demonstrated in a monostatic radar experiment. The measured results clearly show the advantages of the improved antenna.

Detecting and monitoring the micro-motions of trapped people hidden by obstacles based on wavelet entropy with low centre-frequency UWB radar

Efficient detection and monitoring of physiological conditions and activity hidden by walls or rubble are considered challenging in rescue, surveillance, and security operations. In this paper, a new method based on wavelet analysis called wavelet entropy (WE) is proposed to not only detect vital signs but also to monitor the target’s physiological conditions through ultra-wideband (UWB) radar with a centre frequency of 400 MHz. Results of the experiments show that this new method can accurately locate a human target in free space, through a brick wall at a certain distance, and in cases of simulated rubble. Furthermore, a human target’s micro-motion responses due to different physiological conditions with a stationary body in the case of simulated rubble, and that are unrecognizable using common methods, were also quantitatively detected. The WE method not only locates the target’s position but also monitors changes in his/her physiological conditions. This method may also be a useful tool in the practical application of UWB radar.

Microstrip Patch Antennas for Uwb Applications: A Review

The need for development of microstrip patch antennas for ultra-wideband (UWB) communications has been very well recognized.UWB antennas are mainly used for wearable MIMO sytems,weather mesurements and also UWB radar applications. Patch antenna can be a good choice for handheld devices in UWB applications.There was a great success in finding a suitable structure for mobile applications.This paper is a review of various methods that enhance the bandwidth and gain of microstrip patch antennas that specifically used for UWB applications. For instance, the UWB utilizes the frequency band of 3.1-10.6 GHz. Conventionally microstrip antennas operating at narrow band width. Broadening the antenna bandwidth is achieved by using the U-slot technique.The performance of the antenna related with its parameters. The variation of antenna performance depends on variation of location of microstrip feed (L) and the partial ground plane size (G).Length of the antenna is another factor that determines directivity and gain. Use of graded substrate also enhances the directivity and band width.Microstrip antenns are used in satellite communication, military purposes, GPS, mobile, missile systems and many more applications.Simulated and measured results are also used to validate the usefulness of the antenna structure for UWB applications.

A Novel Subnanosecond Monocycle Pulse Generator for UWB Radar Applications

A novel ultra-wideband (UWB) monocycle pulse generator with good performance is designed and demonstrated in this paper. It contains a power supply circuit, a pulse drive circuit, a unique pulse forming circuit, and a novel monopolar-to-monocycle pulse transition circuit. The drive circuit employs wideband bipolar junction transistors (BJTs) and linear power amplifier transistor to produce a high amplitude drive pulse, and the pulse forming circuit uses the transition characteristics of step recovery diode (SRD) effectively to produce a negative narrow pulse. At last, the monocycle pulse forming circuit utilizes a novel inductanceLshort-circuited stub to generate the monocycle pulse directly. Measurement results show that the waveform of the generated monocycle pulses is over 76 V in peak-to-peak amplitude and 3.2 ns in pulse full-width. These characteristics of the monocycle pulse are advantageous for obtaining long detection range and high resolution, when it is applied to ultra-wideband radar applications.

Directive electric–magnetic antenna for ultra‐wideband applications

A novel planar non-dispersive antenna for ultra-wideband radar applications is introduced. The antenna concept is based on the combination of the electromagnetic characteristics of a loop and a planar monopole. A detail discussion on the proposed antenna topology and architecture is presented, and a dedicated backfeeding technique that shows a low transmission loss over a very wide frequency band is suggested. A frequency-independent equivalent circuit of the proposed antenna, useful in the codesign and optimisation of the relevant radio frequency front end is also extracted. It is experimentally demonstrated that the considered radiating element features a fractional bandwidth of 67%, good impedance matching, reasonably constant group delay and uni-directional stable over frequency radiation patterns with front-to-back isolation of about 12 dB.

Application of ultra-wide band radar for classification of human activities

The authors investigate the feasibility of classifying different human activities using ultra-wide band (UWB) radar. Eight human subjects performing eight different activities are measured using a UWB radar. The eight activities include walking, running, rotating, punching, jumping, transitioning between standing and sitting, crawling and standing still. The dimension of the UWB returns is reduced using principal component analysis (PCA). The time-varying UWB signatures are characterised within a time window through observing the variation of the PCA coefficients. A support vector machine (SVM) is used to classify the activities based on the signatures. A multi-class classification is implemented using a one-versus-one method. Optimal parameters for the SVM are found through a 4-fold cross-validation. The resulting classification accuracy is found to be more than 85%. The potential of classifying human activities with different ground planes and with cluttered environments is also investigated. To extract more information regarding the target motion, human walking style classification with the developed method is also discussed.

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.

A Novel Antenna for Transient Applications in the Frequency Band 300 MHz – 3 GHz: The Valentine Antenna

We propose a novel ultrawideband (UWB) antenna designed specially for transient UWB radar applications. This work is a part of a new project concerning an optoelectronic UWB radar demonstrator with an array of four antennas. This project required the development of a new UWB antenna: the Valentine antenna. This antenna must be lighter and more compact in H-plane to allow the assembly of the array. This array must have a volume lower than 1 m3. This antenna, which is composed of curved metallic strips, radiates ultrashort pulses in the frequency band 300 MHz - 3 GHz with very low dispersion, a high gain and a low cross-polarization in the axial direction. The Valentine antenna must support 10kV of peak voltage. This paper describes the Valentine antenna and its main radiation characteristics

Power-efficient switching-based CMOS UWB transmitters for UWB communications and Radar systems

This paper presents a new carrier-based ultra-wideband (UWB) transmitter architecture. The new UWB transmitter implements a double-stage switching to enhance RF-power efficiency, reduce dc-power consumption, and increase switching speed and isolation, while reducing circuit complexity. In addition, this paper also demonstrates a new carrier-based UWB transmitting module implemented using a 0.18-mum CMOS integrated pulse generator-switch chip. The design of a UWB sub-nanosecond-switching 0.18-mum CMOS single-pole single-throw (SPST) switch, operating from 0.45 MHz to 15 GHz, is discussed. The design of a 0.18-mum CMOS tunable impulse generator is also presented. The edge-compression phenomenon of the impulse signal controlling the SPST switch, which makes the generated UWB signal narrower than the impulse, is described. Measurement results show that the generated UWB signal can vary from 2 V peak-to-peak with 3-dB 4-ns pulsewidth to 1 V with 0.5 ns, covering 10-dB signal bandwidths from 0.5 to 4 GHz, respectively. The generated UWB signal can be tuned to cover the entire UWB frequency range of 3.1-10.6 GHz. The sidelobe suppression in the measured spectrums is more than 15 dB. The entire CMOS module works under a 1.8-V supply voltage and consumes less than 1 mA of dc current. The proposed carrier-based UWB transmitter and the demonstrated module provide an attractive means for UWB signal generation for both UWB communications and radar applications

Short-distance ultra wideband radars

The possibility of ultrawideband (UWB) radar usage in various fields for remote measuring the object's motion at short distance is considered. Application of UWB radar in medicine for remote measuring of patient's heart activity and respiration is shown. The measuring method is described and practical results of tests are cited. The opportunity of radar application in other areas is described.