Modulation Continuous Wave Radar Research Articles

A Submicrosecond-Response Ultrafast Microwave Ranging Method Based on Optically Generated Frequency-Modulated Pulses.

An ultrafast microwave ranging method based on optically generated frequency-modulated microwave pulses is proposed in this study. The theoretical analysis demonstrated that nanosecond-scale linear frequency modulation microwave pulse can be obtained by femtosecond laser interference under the condition of unbalanced dispersion, which can be used to achieve a high temporal resolution of the displacement change in the measurement by the principle of frequency modulation continuous wave (FMCW) radar. The proof-of-principle experiment successfully measured the displacement change with an error of 2.5 mm and a range of 0.6 m, with a response time of 468 ns. Compared to existing microwave ranging technologies, the temporal resolution was improved by two orders of magnitude, which greatly improves the temporal resolution of distance measurement in the field of microwave FMCW radar.

A Clutter Identification and Removal Method Based on Long Delay Lines and Cross-Correlation in Through-Wall Detection

Life detection is important in earthquake rescue, but weak vital signal is susceptible to interference by clutters. Due to the undesirable characteristics of the hardware, there are two main types of clutter generated by the frequency modulation continuous wave (FMCW) radar when transmitting signals. One is generated by periodic nonlinearity during frequency modulation, and the other is generated by the phase-locked loop spuriousness (PLLS) in frequency division. They cause additional beat frequencies to appear beside those from the target, leading to false alarms. Since the suppression measures for them are different, it is necessary to distinguish the types of clutter and choose appropriate suppression methods. In this paper, the accurate theoretical modeling of the effects of the periodic nonlinearity and phase-locked loop spuriousness on the beat signal is performed to determine distinctions between them. The clutter occurring in the system used is identified as originating from phase-locked loop spuriousness through fiber-optic experiments. A method using long delay lines and cross-correlation is proposed to identify and remove it. In experiments, the false alarm rate is reduced from over 50 percent to nearly 0 percent, providing strong evidence for the effectiveness of the proposed method in through-wall detection.

Fall Detection Using FMCW Radar to Reduce Detection Errors for the Elderly

Fall accidents pose a significant threat of severe injuries for the elderly, who often need immediate assistance when they fall. Since the use of conventional contact sensors or cameras might be uncomfortable for the user, research on fall detection using non-contact sensors has received considerable attention. While most prior studies have relied heavily on Doppler-based velocity parameters to detect falls, using only Doppler information may lead to erroneous detection of fall-like behavior. As a result, a feature that accounts for additional information is necessary. Addressing this need, this study developed an algorithm for classifying falls by detecting human motions using frequency modulation continuous wave radar, proposing a novel feature to reduce detection errors. The suggested feature was computed using the rangevelocity map of the 2D Fourier transform and evaluated using supervised machine learning techniques, such as support vector machine and linear discriminant analysis, attaining an accuracy higher than 91%.

Real Aperture Continuous Terahertz Imaging System and Spectral Refinement Method

In order to meet the increasing demand of non-destructive testing (NDT) in engineering practice, a continuous terahertz NDT platform based on linear scanning has been developed, with a center frequency of 154 GHz and a bandwidth of 56 GHz. This system combines frequency modulation continuous wave (FMCW) radar technology with a continuous scanning structure, as well as a data acquisition platform to provide a non-contact detection method; this is highly efficient and compensates for the shortcomings of traditional methods such as microwave, X-ray, ultrasonic, and others in safety inspection and special detection. In addition, a signal processing method of spectral refinement and correction is proposed in this paper for accurate thickness measurement. The results show that the method has a high accuracy for ABS, PVC, and ceramic matrix composites. By extracting the characteristic parameters, the detection and imaging of prefabricated defects, such as debonding and bubbles in composite materials, have been successfully achieved. This helps to evaluate the internal state of the inspected object more intuitively and further meets the requirements of industrial NDT.

Cloud Vertical Structure of Stratiform Clouds with Embedded Convections Occurring in the Mei-Yu Front

Cloud Vertical Structure (CVS) plays a crucial role in determining atmospheric circulation and the hydrological cycle. We analyzed the CVS in Stratiform Clouds with Embedded Convection (SCEC) occurring in the mei-yu front over central-eastern China based on the conjunction of the S-band Doppler weather radar, the C-band Frequency Modulation Continuous Wave (C-FMCW) rad ar, and the Microrain Radar (MRR). Our results showed that both the melting layers and the rain rate were unevenly distributed in the three SCEC cases, and there was a thicker melting layer and a larger rain rate in the embedded convection. In the stratiform regions, the vertical velocity of particles in the upper region of the melting layer was generally in the range of 0–4 m·s−1, and increased rapidly to 4–12 m·s−1 near the bottom of the melting layer. In the case of June 28, due to the vigorous development of embedded convection, the cloud particles in the upper layer showed upward movement, and the growth rate of the particles in this region was faster than that in the surrounding stratiform regions. The vertical distributions of Drop Spectrum Distributions (DSDs) showed that the average concentration of drops larger than 3 mm increased as they fell from 3 km to 1 km, and the collision–coalescence process of drops in the embedded convection was stronger.

A 78.8-84 GHz Phase Locked Loop Synthesizer for a W-Band Frequency-Hopping FMCW Radar Transceiver in 65 nm CMOS.

A W-band integer-N phase-locked loop (PLL) for a frequency hopping frequency modulation continuous wave (FMCW) radar is implemented in 65-nm CMOS technology. The cross-coupled voltage-controlled oscillator (VCO) was designed based on a systematic analysis of the VCO combined with its push-pull buffer to achieve high efficiency and high output power. To provide a frequency hopping functionality without any overhead in the implementation, the center frequency of the VCO is steeply controlled by the gate voltage of the buffer, which effectively modifies the susceptance of the VCO load. A stand-alone VCO with the proposed architecture is fabricated, and it achieves an output power of 13.5 dBm, a peak power efficiency of 9.6%, and a tuning range of 3.5%. The phase noise performance of the VCO is −92.6 dBc/Hz at 1-MHz and −106.1 dBc/Hz at 10 MHz offset. Consisting of a third-order loop filter and a divider chain with a total modulus of 48, the locking range of the implemented PLL with the cross-coupled VCO is recorded from 78.84 GHz to 84 GHz, and its phase noise is −85.2 dBc/Hz at 1-MHz offset.

ColoRadar: The direct 3D millimeter wave radar dataset

This work presents two different forms of dense, high-resolution radar data from two frequency modulated continuous wave radar sensors, along sparse radar pointclouds produced by one of the radar sensors. In addition, all datasets include 3D lidar and inertial measurements, and a lidar-based simultaneous localization and mapping pose estimation. Over 2 h of 6D pose data was generated across 52 datasets collected in highly diverse 3D environments including lab spaces, outside and inside large buildings, urban walkways, and a mine. One dataset, from the ASPEN Lab, also includes precision groundtruth generated from a motion capture system. Intrinsic radar calibration and measured extrinsic sensor position calibrations are also provided along with python based development tools to interact with the various datasets. This data is designed to assist with generating radar based localization algorithms and calibrations between radar and other sensors.

Tracking of Evasive Objects Using Bistatic Doppler Radar Operating in the Millimeter Wave Regime

In this study, we propose a range detection (RD) ability by a continuous wave (CW) bistatic Doppler radar (RDCWB) of small and fast targets with very high range resolution. The target’s range and velocity are detected simultaneously. The scheme is based on the transmission of a continuous wave (CW) at millimeter wavelength (MMW) and the measurement of the respective Doppler shifts associated with target movements in different directions. The range resolution in this method is determined by the Doppler resolution only, without the necessity to transmit the modulated waveforms as in frequency modulation continuous wave (FMCW) or pulse radars. As the Doppler resolution in CW depends only on the time window required for processing, a very highrange resolution can be obtained. Most other systems that perform target localization use the transmission of wide-band waveforms while measuring the delay of the received signal scattered from the target. In the proposed scheme, the range resolution depends on the processed integration time of the detected signal and the velocity of the target. The transmission is performed from separated antennas and received by a single antenna. The received signal is heterodyned with a sample of the transmitted signal in order to obtain the Doppler shifts associated with the target’s movement. As in a multi-in multi-out (MIMO) configuration, the presented scheme allows for the accumulation of additional information for target classification. Data on the target’s velocity, distance, direction, and instantaneous velocity can be extracted. Using digital processing, with the additional information obtained by analyzing the difference between the resulting intermediate frequencies caused by the Doppler effect, it is possible to calculate the distance between the radar and the target at high resolution in real-time. The presented method, which was tested experimentally, proved to be highly effective, as only one receiver is required for the detection, while the transmission is carried out using a fixed, single-frequency transmission.

Determination of Fast-Moving Objects’ Speed and Range with Linear Frequency Modulation Continuous Wave Radar Using Autocorrelation Scheme

Introduction. A hardware basis of modern Advanced Driver Assistance Systems (ADAS) consists of millimeterrange radars, characterized by a relatively short range (meters – tens of meters). At the same time, improving of traffic safety requires to increase the range at least to several hundred meters. The one way to achieve such values is to increase wavelength of a probing signal, to use the centimeter range of wavelengths, for example. The paper represents a detailed description of main steps of signal processing algorithm in the model of the ADAS low-power centimeter range radar, which provides fast-moving objects speed and range definition.Aim. Development of an algorithm for estimating the range and the speed of targets by an autocorrelation radar with a wide-band continuous linear frequency modulation (linear FM) signal in order to increase the rate of the ADAS system estimates formation.Materials and methods. The proposed algorithm is based on the methods of primary and secondary digital processing of radar signals. The model of a centimeter-range autocorrelation radar with a broadband continuous linear FM probing signal was used for practical researches. MATLAB software was used to process the received signal samples.Results. The algorithm has been developed to determine the speed and the range of fast-moving objects in conditions when their movement during the evaluation interval significantly exceeds the radar range resolution. The use of simplified Kalman filtering for inter-period secondary signal processing allowed to increase significantly the stability of the algorithm. In a full-scale experiment using the low-power radar model with continuous radiation of the centimeter range, it was shown that a stable assessment of a real car speed and range was provided at a distance of at least about one kilometer.Conclusion. The results of the field experiment make it possible to draw conclusions that the proposed algorithm is highly robust even in the absence of inter-period secondary processing. Its usage allows one to improve the stability of the algorithm without considerable additional computational costs. It is possible because near-linear dynamics of the observation object and of the radar carrier makes it sufficient to use a simplified implementation of Kalman filter in the form α-β-algorithm.

Research on LFMCW Radar Velocity Ranging Optimization System Based on FPGA

Abstract Linear frequency modulation continuous wave (LFMCW) radar is widely used in the field of velocity measurement and ranging because of its high precision and good range resolution. The traditional LFMCW radar uses a single core FFT to do data processing, which is not very fast. This article utilize that advantages of fast and high degree of integration of FPGA, and propose a double-core FFT processor based on the use of the optimized CORDIC parallel algorithm to improve data processing speed, enhance real time, design and realize the calculation module of the double-core FFT data processing module and the distance measuring speed, and finishes the design of the LFMCW radar speed measuring and measuring system with real time and quick advantages. The experimental results show that the system has the characteristics of fast data processing and high reliability, and can measure the moving vehicle in real time and effectively.

Cascaded Kalman filter for target tracking in automotive radar

In automotive anti-collision radar system, the accuracy of velocity is one of the key indicators to measure radar performance. For frequency modulation continuous wave radar with chirp sequence, which is commonly used in automotive radar, there are two problems that are velocity ambiguity and measurement error. In order to address these problems, a cascaded Kalman filter algorithm is proposed in this article, which is able to overcome velocity ambiguity and improve the accuracy of measurements. In addition, the problem of velocity ambiguity can be solved just in the data processing and it avoids transmitting staggered or multiple pulse repetition frequency signal. The simulation results show that this algorithm can effectively improve the tracking performance.

Low cost FMCW radar systems with the reduced number of FFT points under indoor environments

In this paper proposed is a cost-efficient signal processing algorithm of a frequency modulation continuous wave (FMCW) radar for the close range under indoor environments. Recently, the use of an FMCW radar has been expanded to short distance from long distance due to easy production and inexpensive designing costs. In order to obtain satisfying resolution of the close range radar, it still requires a wide modulation bandwidth, which results in high costing wideband RF devices. This paper proposes a cost-efficient signal processing method using correlations between a reflected signal in frequency-domain and a lookup table which holds the frequency information depending on distances. The proposed algorithm shows the similar performance to a wideband system just by updating a firmware of low costing narrowband RF FMCW radar devices without additional hardware modification.

Detection of oil in and under ice

ABSTRACT (2017-147) In 2014, researchers from ten organizations came to the U.S. Army Corps of Engineers, Cold Regions Research and Engineering Laboratory (CRREL) in New Hampshire to conduct a first of its kind large-scale experiment aimed at determining current sensor capabilities for detecting oil in and under sea ice. This project was the second phase of the Oil Spill Detection in Low Visibility and Ice research project of the International Association of Oil and Gas Producers (IOGP), Arctic Oil Spill Response Technology - Joint Industry Programme. The objectives of the project were to:Acquire acoustic, thermal, optical and radar signatures of oil on, within, and underneath a level sheet of laboratory sea ice.Determine the capabilities of various sensors to detect oil in specific ice environments created in a test tank, including freeze-up, growth and melt.Model the potential performance of the sensors under realistic field conditions using the test data for validation.Recommend the most effective sensor suite of existing sensors for detecting oil in the ice environment. The sensor testing spanned a two-month ice growth phase and a one-month decay/melt period. The growth phase produced an 80 centimeter thick level sheet of salt water ice representative of natural sea ice grown under quiescent conditions. Above-ice sensors included frequency modulated continuous wave radar, ground penetrating radar, laser fluorescence polarization sensor, spectral radiometer, visible and infrared cameras. Below-ice sensors included acoustics (broadband, narrowband, and multibeam sonars), spectral radiometers, cameras, and fluorescence polarization. Measurements of physical and electrical properties of the ice and oil within the ice were provided to optical, acoustic, and radar modelers as inputs into their models. The models were then used to extrapolate the sensors’ laboratory performance to potential performance over a range of field conditions. All selected sensors detected oil under some conditions. The radar systems were the only above-ice sensors capable of detecting oil below or trapped within the ice. Cameras below the ice detected oil at all stages of ice growth, and the acoustic and fluorescence systems detected encapsulated oil through limited amounts of new ice growth beneath the oil. No single sensor detected oil in and below ice under all conditions tested. However, we used the test results to identify suites of sensors that could be deployed today both above and below the ice to detect and map an oil spill within ice covered waters.

Drone Classification Using Convolutional Neural Networks With Merged Doppler Images

We propose a drone classification method based on convolutional neural network (CNN) and micro-Doppler signature (MDS). The MDS only presents Doppler information in time domain. The frequency domain representation of MDS is called as cadence-velocity diagram (CVD). To analyze the Doppler information of drone in time and frequency domain, we propose a new image by merging MDS and CVD, as merged Doppler image. GoogLeNet, a CNN structure, is utilized for the proposed image data set because of its high performance and optimized computing resources. The image data set is generated by the returned Ku-band frequency modulation continuous wave radar signal. Proposed approach is tested and verified in two different environments, anechoic chamber and outdoor. First, we tested our approach with different numbers of operating motor and aspect angle of a drone. The proposed method improved the accuracy from 89.3% to 94.7%. Second, two types of drone at the 50 and 100 m height are classified and showed 100% accuracy due to distinct difference in the result images.

System for Automatic Detection and Analysis of Targets in FMICW Radar Signal

Abstract This paper presents the automatic system for the processing of the signals from the frequency modulated interrupted continuous wave (FMICW) radar and describes methods for the primary signal processing. Further, we present methods for the detection of the targets in strong noise. These methods are tested both on the real and simulated signals. The real signals were measured using the developed at the IAP CAS experimental prototype of FMICW radar with operational frequency 35.4 GHz. The measurement campaign took place at the TU Delft, the Netherlands. The obtained results were used for development of the system for the automatic detection and analysis of the targets measured by the FMICW radar.

Long‐distance imaging with frequency modulation continuous wave and inverse synthetic aperture radar

In a frequency modulation continuous wave and inverse synthetic aperture radar (FMCW–ISAR) system, imaging a target beyond the maximum unambiguous range causes the ambiguity in the range domain. This ambiguity phenomenon greatly reduces resolution and degrades image quality, and limits the application of long-distance imaging of an FMCW–ISAR system. In this study, ambiguity correction method, based on mutual-coherence processing, is proposed for long-distance imaging in an FMCW–ISAR system. In the process, the singularity point of the beat signal caused by the ambiguity phenomenon is determined by the wavelet transform modulus maxima method. All-pole models are used to fit the beat signal subbands of different Doppler frequencies, and then adjust the models until they optimally match. The simulation results validate the effectiveness of the proposed correction method. This study shows the promising prospect of long-distance imaging using an FMCW–ISAR system.

Master Control System Design for Frequency Modulation Continuous Wave Radar (FMCW)

This paper introduces the definition and composition of vehicle collision avoidance system; describes function requirements of the vehicle anti-collision system; researched and developed the related source code using LabVIEW virtual instrumental technology; solved the NI data acquisition card and anti-collision system matching problem, and completed master control program designs of the automobile anti-collision alarm system. By using a sensor device, the system can measure the car's overall performance at any time.

Correction of Dechirp Distortion in Long-Distance Target Imaging with LFMCW-ISAR

The combined linear frequency modulation continuous wave (LFMCW) and inverse synthetic aperture radar (ISAR) can be used for imaging long-distance targets because of its long-distance and high resolution imaging abilities. In this paper, we find and study the dechirp distortion phenomenon (DDP) for imaging long-distance targets by a dechirp-on-receive LFMCW radar. If the targets are very far from the radar, the maximum delay-time is not much smaller than a single sweep duration, and the dechirp distortion is triggered since the distance of the target is unknown in a LFMCW-ISAR system. DDP cannot be ignored in long-distance imaging because double images of a target appear in the frequency domain, which reduces resolution and degrades image quality. A novel LFMCW-ISAR signal model is established to analyze DDP and its negative effects on long-distance target imaging. Using the proportionately distributed energy of double images, the authors propose a method to correct dechirp distortion. In addition, the applicable scope of the proposed method is also discussed. Simulation results validate the theoretical analysis and the effectiveness of the proposed method.

Sparse Detection in the Chirplet Transform: Application to FMCW Radar Signals

This paper aims to detect and characterize a signal coming from frequency modulation continuous wave radars. The radar signals are made of piecewise linear frequency modulations. The maximum chirplet transform (MCT), a simplification of the chirplet transform is proposed. A detection of the relevant maximum chirplets is proposed based on iterative masking, an iterative detection followed by window subtraction that does not require the recomputation of the spectrum. This detection is designed to provide a sparse subset of maximum chirplet coefficients. The chirplets are then gathered into linear chirps whose starting time, length, and chirprate are estimated. These chirps are then gathered again back into the different frequency modulation continuous wave signals, ready to be classified. An illustration is provided on synthetic data.

Based on the LabVIEW Frequency Modulation Continuous Wave Radar Signal Acquisition and Processing

This paper introduces the FMCW anti-collision radar system, introduces the concept of virtual instrument and LabVIEW characteristics. The use of LabVIEW virtual instrumental technology, research and development of the related code, the virtual completion signal acquisition system design, at any time on the echo signal acquisition and processing, the calculation result and the safety distance data are compared to determine whether the alarm.