Radar Range Research Articles

Low-Complexity Joint Range and Doppler FMCW Radar Algorithm Based on Number of Targets.

A low-complexity joint range and Doppler frequency-modulated continuous wave (FMCW) radar algorithm based on the number of targets is proposed in this paper. This paper introduces two low-complexity FMCW radar algorithms, that is, region of interest (ROI)-based and partial discrete Fourier transform (DFT)-based algorithms. We find the low-complexity condition of each algorithm by analyzing the complexity of these algorithms. From this analysis, it is found that the number of targets is an important factor in determining complexity. Based on this result, the proposed algorithm selects a low-complexity algorithm between two algorithms depending the estimated number of targets and thus achieves lower complexity compared two low-complexity algorithms introduced. The experimental results using real FMCW radar systems show that the proposed algorithm works well in a real environment. Moreover, central process unit time and count of float pointing are shown as a measure of complexity.

Highly Linear Phase-Canceling Self-Injection-Locked Ultrasonic Radar for Non-Contact Monitoring of Respiration and Heartbeat.

A novel phase-canceling demodulation scheme to improve the linearity of a self-injection-locked (SIL) ultrasonic radar is proposed with the goal of solving the null detection problem and accurately sensing large displacements of a moving target. A proportional-integral (PI) controller regulates the phase of the injection signal and cancels the Doppler phase shift by tuning a delay in the received echo signal, and this tunable delay serves as the radar output, which is linearly proportional to the displacement of the target. Without assuming weak injection, the frequency and phase equations for an SIL oscillator are derived, supporting the construction of a plant model and the design of a PI controller. Also, a new ultrasonic radar equation is presented for estimating the radar detection range. The SIL radar with phase regulation is operated in its anti-phase injection mode for better performance. The proposed design is implemented on an FPGA to make a 40kHz continuous-wave ultrasonic radar. The maximum detectable peak-to-peak motion is up to 120 mm (approximately 14 wavelengths of displacement), with a total harmonic distortion as low as 2.3% for the detection of 1Hz harmonic motion. The radar is used to detect the human chest movement for non-contact monitoring of the respiratory rate and heart rate. Due to the high linearity and sensitivity, the radar is capable of faithfully detecting the relatively large involuntary body movements and lung movements while still preserving the weak heartbeat rhythm buried in them, with the average error of measured heart rates less than 1 BPM.

О ПРИМЕНИМОСТИ ФАЗОВОГО МЕТОДА СКАНИРОВАНИЯ В АНТЕННЫХ РЕШЕТКАХ ИМПУЛЬСНЫХ ЛЧМ-РАДАРОВ

О ПРИМЕНИМОСТИ ФАЗОВОГО МЕТОДА СКАНИРОВАНИЯ В АНТЕННЫХ РЕШЕТКАХ ИМПУЛЬСНЫХ ЛЧМ-РАДАРОВ

Features of construction of the scheme of fiber-optic communication system for transmission of analog signals in the frequency range from 0.135 to 40 GHz

The paper presents the design of a fiber-optic microwave signal transmission line. The use of the developed design of a fiber-optic microwave transmission line allows the radar operating frequency range to be at least doubled. In addition, the number of functional blocks is reduced to ensure the operation of the radar in this frequency range. The results of experimental studies are presented.

Analysis and Optimization of Ambiguity Function in Radar-Communication Integrated Systems Using MPSK-DSSS

With increasingly sophisticated electromagnetic environment of combat platforms, radar communication integration has attracted wide interests. In this letter, instead of designing a new integrated signal, we employ multiple-phase shift keying direct sequence spread spectrum (MPSK-DSSS) signal as radar communication integrated signal due to its advantage of outstanding correlation. On the one hand, the closed form expression of average ambiguity function is obtained, by which we can analyze the relationship between parameters of integrated signal and radar range resolution. On the other hand, to improve radar peak sidelobe level (PSL) influenced by random communication signals, we propose a joint optimization method based on sequence mapping at the transmitter and sidelobe suppression at the radar receiver. Simulation results show that the sidelobe levels of the optimized integrated signal is effectively suppressed at the cost of slight communication rate loss.

Electromagnetic wave propagation based upon spectral-element methodology in dispersive and attenuating media

SUMMARYWe build on mathematical equivalences between Maxwell’s wave equations for an electromagnetic medium and elastic seismic wave equations. This allows us to readily model Maxwell’s wave propagation in the spectral-element codes SPECFEM2D and SPECFEM3D, written for acoustic, viscoelastic and poroelastic seismic wave propagation, providing the ability to handle complex geometries, inherent to finite-element methods and retaining the strength of exponential convergence and accuracy due to the use of high-degree polynomials to interpolate field functions on the elements, characteristic to spectral-element methods (SEMs). Attenuation and dispersion processes related to the frequency dependence of dielectric permittivity and conductivity are also included using a Zener model, similar to shear attenuation in viscoelastic media or viscous diffusion in poroelastic media, and a Kelvin–Voigt model, respectively. Ability to account for anisotropic media is also discussed. Here, we limit ourselves to certain dielectric permittivity tensor geometries, in order to conserve a diagonal mass matrix after discretization of the system of equations. Doing so, simulation of Maxwell’s wave equations in the radar frequency range based on SEM can be solved using explicit time integration schemes well suited for parallel computation. We validate our formulation with analytical solutions. In 2-D, our implementation allows for the modelling of both a transverse magnetic (TM) mode, suitable for surface based reflection ground penetration radar type of applications, and a transverse electric (TE) mode more suitable for crosshole and vertical radar profiling setups. Two 2-D examples are designed to demonstrated the use of the TM and TE modes. A 3-D example is also presented, which allows for the full TEM solution, different antenna orientations, and out-of-plane variations in material properties.

Target Positioning With Surveillance Radar by the Estimation of Atmospheric Refractivity Profile

The positioning of a target with radar measurements could be inaccurate because of the atmospheric refraction effects. We present a technique for determining the refractivity parameters using known position information of cooperative targets. The estimated refractivity parameters are then used to find the position of a noncooperative target, along with its radar range and angle measurements. The performance of the proposed algorithm is assessed by comparing the mean squared error of the estimate with the Cramer–Rao lower bound as well as by testing the algorithm with real field data. Ground-based military surveillance radar can adopt the proposed algorithm and benefit when there are some cooperative flying aircraft while there is no external refractivity information such as radiosonde data.

Broadband Low-RCS Phased Array With Wide-Angle Scanning Performance Based on the Switchable Stacked Artificial Structure

A novel and simple switchable stacked artificial structure (SAS) is proposed and studied in phased arrays to realize a smart integration of broadband radar cross section (RCS) reduction and scanning range expansion. The proposed SAS is composed of a frequency selective surface (FSS) and a metamaterial absorber (MA). The lower part of the SAS can be switched between an FSS and a surface-waveguide (SWG) high-impedance surface (HIS) hybrid structure which can be used for wide-beam antenna design and array mutual coupling reduction. The upper part of the SAS can be seen as an MA. A linear phased array is presented and investigated based on the proposed switchable SAS. When the phased array is switched to its working mode, the SWG-HIS hybrid structure plays an important role to support a wide-angle scan from −75° to +75° with low sidelobes. When the phased array is shut down, the FSS-MA stacked structure can realize a low-RCS design in the frequency range of 0–11.2 GHz. An array prototype which operates at 4.6 GHz is fabricated and measured. The measured results have validated the radiation and scattering performance of the designed phased array.

Target separation detection and motion parameter estimation method based on time‐varying autoregressive model

The authors report a target separation detection and motion parameter estimation method based on the time-varying autoregressive (TVAR) model. The TVAR model is used to extract the instantaneous Doppler frequencies of multiple targets or scattering points in a same radar range cell, and the motion parameters are estimated based on the Doppler frequencies at every pulse time in a radar frame. In particular, for coherent multipulse echo signal, the TVAR model is first utilised to extract multiple instantaneous Doppler frequencies at each pulse time, thus forming a Doppler frequency matrix. Second, the Doppler tracking and polynomial fitting methods are utilised to estimate the radial velocity and acceleration based on the Doppler frequency matrix. Finally, the target separation detection is achieved by acquiring and validating multiple Doppler frequency components in the same range cell. Simulations and verifications are carried out, and the results show that the proposed method is effective for target separation detection and precision motion parameter estimation, which could be of great value radar target detection, tracking, and automatic target recognition.

Polarised HRRP scattering centre estimation via atomic norm minimisation

The combination of polarisation and high-resolution technology is a promising research direction for radar automatic target recognition. Fusing the polarisation information into the scattering centre model is able to refine the scattering structural information. This study proposes a fully-polarised radar high range resolution profile (HRRP) scattering centre estimation method based on a multiple measurement vector atomic norm minimisation model. The estimation is performed in a continuous domain, thus avoids the basis mismatch problem. The experimental results demonstrate the superiorities of the proposed method in terms of accuracy and robustness.

DOA Estimation Performance Analysis and Verification of Dual Crossed-Loop/Monopole Antenna Array

The compact high-frequency surface wave radar using a crossed-loop/monopole (CLM) antenna as the receiving sensor has been widely used in ocean remote sensing and target monitoring. However, the direction of arrival (DOA) estimation accuracy of a single CLM antenna is the dominant factor that restricts the target monitoring performance of the compact HF radar. Besides, the single CLM antenna can estimate two signals simultaneously at most, but its effectiveness is challenged by the pattern distortion and the existence of coherent sources, which limits the application range of the compact HF radar. In this study, a compact array combining two CLM antennas is proposed to improve the DOA estimation accuracy and solve the multisource DOA estimation problem. The estimation error and multisource DOA estimation performance of a dual CLM antenna array are analyzed by formula derivation and simulation. Furthermore, the field experiment results are given to demonstrate the performance improvement of the dual CLM antenna array.

Moving-target indication in ultra wideband radar

The article describes the principle of implementation of an UWB sounding signal for short range radar. The comparative analysis of UWB signals classification variants is made. A mathematical model of the formation of an ultrashort radio pulse from a video pulse is presented. The use of ultrashort radio pulses does not have difficulties in technical implementation and makes it possible to achieve high stability of the parameters of the sounding signal. The options for estimating speeds for UWB systems are considered. The method for moving-target indication and their separation from the underlying surface for UWB radars is proposed. The method uses coherent integration with subsequent spectral analysis based on Fast Fourier Transformation. Experimental studies of the proposed method of moving-target indication are made. The results of experiments prove the proposed method efficiency.

An Accurate and Compact High Power Monocycle Pulse Transmitter for Microwave Ultra-Wideband Radar Sensors with an enhanced SRD model: Applications for Distance Measurement for lossy materials

In This paper, a high power sub-nanosecond pulse transmitter for Ultra-wideband radar sensor is presented. The backbone of the generator is considered as a step recovery diode and unique pulse injected into the circuit, which gives rise to an ultra-wide band Gaussian pulse. The transistor driver and transmission line pulse forming the whole network are investigated in detail. The main purpose of this work is to transform a square waveform signal to a driving pulse with the timing and the amplitude parameters required by the SRD to form an output Gaussian pulse, and then into high monocycle pulses. In simulation aspect, an improved output response is required, in this way a new model of step recovery diode has been proposed as a sharpener circuit. This proposition was applied to increase the rise-time of the pulses. For a good range radar, a high amplitude pulse is indispensable, especially when it comes to penetrate thick lossy materiel. In order to overcome this challenge, a simple technique and useful solution is introduced to increase the output amplitude of the transmitter. This technique consists to connect the outputs of two identical pulse generators in parallel respecting the restrictions required. The pulse transmitter circuit is completely fabricated using micro-strip structure technology characteristics. Waveforms of the generated monocycle pulses over 10V in amplitude with 3.5 % in overshoot have been obtained. Good agreement has been achieved between measurement and simulation results.

LFM-PC Radar Evaluation in Presence of Jamming using SystemVue

Pulse Compression (PC) radars become; now a day; are the most commonly used in a lot of military applications. This is due to its capability to resolve the problem of designing long range radar with excellent range resolution. Also, it provides additional processing gain that enhances radar detection capability. Moreover, Pulse compression is considered as an electronic counter countermeasures (ECCM) capability. It provides the radar with a good immunity against different jamming techniques. There are a lot of types of PC waveforms. Linear Frequency Modulated (LFM) signals are the most tolerant to high Doppler shifts. This is why LFM-PC radars are widely utilized with high speed targets. However, the literature lacks a simulation model to evaluate the detection performance of LFM-PC radar in presence of different noise jamming techniques. This paper introduces a typical simulation model for LFM-PC search radar using SystemVue. The simulated model allows the studying of the PC radar performance with different jamming techniques. Also, the optimum jamming technique; from electronic warfare point of view; is explored.

Radar Measurements of Morphological Parameters and Species Identification Analysis of Migratory Insects

Migratory insect identification has been concerning entomology and pest managers for a long time. Their nocturnal behavior, as well as very small radar cross-section (RCS), makes individual detection challenging for any radar network. Typical entomological radars work at the X-band (9.4 GHz) with a vertical pencil beam. The measured RCS can be used to estimate insect mass and wingbeat frequency, and then migratory insects can be categorized into broad taxon classes using the estimated parameters. However, current entomological radars cannot achieve species identification with any higher precision or confidence. The limited frequency range of current insect radars have precluded the acquisition of more information useful for the identification of individual insects. In this paper, we report an improved measurement method of insect mass and body length using a radar with many more measurement frequencies than current entomological radars. The insect mass and body length can be extracted from the multi-frequency RCSs with uncertainties of 16.31% and 10.74%, respectively. The estimation of the thorax width and aspect ratio can also be achieved with uncertainties of 13.37% and 7.99%, respectively. Furthermore, by analyzing the statistical data of 5532 insects representing 23 species in East China, we found that the correct identification probabilities exceed 0.5 for all of the 23 species and are higher than 0.8 for 15 of the 23 species under the achievable measurement precision of the proposed technique. These findings provide promising improvements of individual parameter measurement for entomological radars and imply a possibility of species identification with higher precision.

Six‐element dual polarized high‐gain MIMO antenna for multiband applications

AbstractA planar six‐elements, dual‐polarized, high‐gain, multiband antenna for diverse application is proposed in this manuscript. The proposed design consists of six radiating elements and a parasitic element on the top side of the structure. Each radiating element consists of overlapped ellipse with a line feeding technique. Iterations have been carried out on the number of antenna elements as well as on the spacing between the elements to get a minimum coupling between antenna elements. To compensate the coupling effect as well as to increase the impedance bandwidth, a ground plane structure has been modified with “L” shape structures. Fabricated prototype has an isolation less than −2 dB with highest gain of 6.7 dBi. Diversity in polarization is achieved by orienting antenna elements in vertical as well as in horizontal directions. A simple and compact design of antenna with good gain and less correlation coefficient makes an antenna useful for multiple input multiple output (MIMO) applications in the wireless communication systems. Simulation and measurement results validates the use of proposed structure in various applications like ISM, WLAN, Wi‐Fi, short range radar, and satellite applications.

U-DeepHand: FMCW Radar-Based Unsupervised Hand Gesture Feature Learning Using Deep Convolutional Auto-Encoder Network

Recently, although radar sensors have been widely applied for hand gesture recognition (HGR) tasks, conventional radar-based HGR systems still have two major challenges. First, these systems rely on supervised learning approaches to learn gesture features, which normally require a large-scale labeled dataset to address the overfitting problem. However, the acquisition of such dataset is time-consuming. Second, the radar signature of hand movement is often influenced by micromotion caused by other body parts, which leads to distorted motion features, resulting in poor identification accuracy. To overcome these problems, we propose an unsupervised hand gesture feature learning method using the deep convolutional auto-encoder network to analyze hand gesture signal collected by a frequency modulated continuous wave (FMCW) radar sensor. First, via a convolutional encoder sub-network, input radar range profiles are transformed into lower dimensional representations. Then, the representations are expanded to reconstruct the corresponding input profiles by a deconvolutional decoder sub-network. In addition, to investigate the mechanisms of the proposed network and evaluate its performance, we conduct an in-depth study of the feature maps learned from various hand gesture experimental data and evaluate the corresponding classification performance. The results demonstrate that the proposed convolutional auto-encoder network is able to achieve high recognition accuracy with low training sample cost, which outperforms the state-of-the-art hand gesture recognition systems based on transfer learning VGGNet and fully connected-based auto-encoder network.

LaIF: A Lane-Level Self-Positioning Scheme for Vehicles in GNSS-Denied Environments

Vehicle self-positioning is of significant importance for intelligent transportation applications. However, accurate positioning (e.g., with lane-level accuracy) is very difficult to obtain due to the lack of measurements with high confidence, especially in an environment without full access to a global navigation satellite system (GNSS). In this paper, a novel information fusion algorithm based on a particle filter is proposed to achieve lane-level tracking accuracy under a GNSS-denied environment. We consider the use of both coarse-scale and fine-scale signal measurements for positioning. Time-of-arrival measurements using the radio frequency signals from known transmitters or roadside units, and acceleration or gyroscope measurements from an inertial measurement unit (IMU) allow us to form a coarse estimate of the vehicle position using an extended Kalman filter. Subsequently, fine-scale measurements, including lane-change detection, radar ranging from the known obstacles (e.g., guardrails), and information from a high-resolution digital map, are incorporated to refine the position estimates. A probabilistic model is introduced to characterize the lane changing behaviors, and a multi-hypothesis model is formulated for the radar range measurements to robustly weigh the particles and refine the tracking results. Moreover, a decision fusion mechanism is proposed to achieve a higher reliability in the lane-change detection as compared to each individual detector using IMU and visual (if available) information. The posterior Cramer–Rao lower bound is also derived to provide a theoretical performance guideline. The performance of the proposed tracking framework is verified by simulations and real measured IMU data in a four-lane highway.

Research on Optimization of Working Mode of Long-range Early Warning Radar Guided by Space-based Information

The long-range early warning radar is the key equipment in the early defense process of ballistic missile. For the problem of low working efficiency of long-range early warning radar without guidance information, this paper studies the working process of long-range early warning radar with space-based guidance information, and proposed a new long-range warning radar working mode. Firstly, the coordinate system transformation and guidance information extraction of space-based guidance information are given. Then the concept of coherent accumulation of radar signals is introduced and a new radar operation mode is proposed. Finally, the radar signal coherent accumulation process is established. A mathematical model of radar search distance and intercept probability. The typical scene is built and simulated. The results show that the proposed radar working mode will effectively reduce the search airspace of the long-range early warning radar and improve the radar detection range.

Radar high‐resolution range profile recognition via multi‐SV method

The radar high-resolution range profile (HRRP) is of great significance for target recognition in the ground compound environment. As two essential processes of HRRP target recognition, discrimination and classification performance improvement are studied in this study. A novel target recognition method is designed, denoted by multiple support vector (SV) method. In the training phase, a multiple correlate SV model is constructed, which separates the multi-target feature space into several central-coherence distributed regions. Each region has been described by the modified SV method, and the category determination is based on the description of multiple regions. This method can overcome the issues of both outlier discrimination and targets classification. Due to the hierarchical process in the testing phase, this method needs less memory and calculation to fit the practical radar target recognition task. Finally, the experiment based on the measured data verifies the excellent performance of this method.