10,049 results on '"RADAR"'
Search Results
2. Zoltan Bay and the First Moon-Radar Experiment in Europe (Hungary, 1946).
- Author
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Kovacs, Laszlo
- Abstract
Describes the first moon-radar echo experiment conducted by Zoltan Bay in Hungary and comments on Bay as a model for contemporary physics education. (DDR)
- Published
- 1998
3. Shipboard Electronic Equipments.
- Author
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Naval Personnel Program Support Activity, Washington, DC. and Bureau of Naval Personnel, Washington, DC.
- Abstract
Fundamentals of major electronic equipments on board ships are presented in this text prepared for naval officers in general. Basic radio principles are discussed in connection with various types of transmitters, receivers, antennas, couplers, transfer panels, remote-control units, frequency standard equipments, teletypewriters, and facsimile installations. Theoretical and practical analyses are made of radar and sonar equipments to show their capabilities and limitations. On the subject of electronic navigation, loran, shoran, omega, tacan, and satellite and ships' inertial navigation systems are presented. Also included are descriptions of digital computers, gun and missile weapon systems, direction finders, closed-circuit television sets, electronic countermeasures, communication console equipments, underwater telephones, intrared and meteorological setups, carrier control approach systems, radiac instruments, and target control installations. Illustrations for explanation purposes and a glossary of general terms are included. (CC)
- Published
- 1969
4. Discovering the Invisible Universe.
- Author
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Friedman, Herbert
- Abstract
The discovery of radio waves, infrared, and x-rays and their importance in describing the universe and its origins is discussed. Topics include radio waves from space, the radio pioneers of World War II, radio telescopes, infrared radiation, satellites, space missions, and x-ray telescopes. (KR)
- Published
- 1991
5. Single Antenna X-Band Doppler Shift Apparatus
- Author
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Simpson, R. E.
- Published
- 1969
6. Materials for a Radar Ranging Experiment
- Author
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Fowler, J. M.
- Published
- 1969
7. Lasers in Industry
- Author
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James, H.
- Published
- 1970
8. Two Undergraduate Microwave Experiments Giving Unexpected Data
- Author
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Reichert, Jonathan F.
- Published
- 1972
9. The Doppler Effect--A New Approach
- Author
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Allen, J.
- Abstract
Discusses the Doppler effect as it applies to different situations, such as a stationary source of sound with the observer moving, a stationary observer, and the sound source and observer both moving. Police radar, satellite surveillance radar, radar astronomy, and the Doppler navigator, are discussed as applications of Doppler shift. (JR)
- Published
- 1973
10. The DC8 as an Exemplar of Relevant Physics
- Author
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Lockett, T. K.
- Abstract
Presents data on aircraft take off and landing, including measurements of turning speeds, triangle of velocities method, fuel consumption, air pressure differences, air turbulence, maintenance inspection, and airborne radar. Indicates the materials can serve as relevant physics examples in teaching sixth and seventh form pupils. (CC)
- Published
- 1974
11. How Things Work--Doppler Radar: The Speed of the Air in a Tornado.
- Author
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Crane, H. Richard
- Abstract
Describes the nature, history, and applications of Doppler radar detecting the speed of moving object. Gives an example of measuring the radial velocity of a scattered wave. (YP)
- Published
- 1989
12. Apparatus Notes
- Published
- 1972
13. Spatial Simultaneous Functioning-Based Joint Design of Communication and Sensing Systems in Wireless Channels
- Author
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Pham Ngoc Luat, Attaphongse Taparugssanagorn, Kamol Kaemarungsi, and Chatchamon Phoojaroenchanachai
- Subjects
JCAS ,communications ,radar ,sensing ,signal processing ,deep learning ,Technology ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Biology (General) ,QH301-705.5 ,Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
This paper advocates for spatial simultaneous functioning (SSF) over time division multiple access (TDMA) in joint communication and sensing (JCAS) scenarios for improved resource utilization and reduced interference. SSF enables the concurrent operation of communication and sensing systems, enhancing flexibility and efficiency, especially in dynamic environments. The study introduces joint design communication and sensing scenarios for single input single output (SISO) and multiple input multiple output (MIMO) JCAS receivers. An MIMO-JCAS base station (BS) is proposed to process downlink communication signals and echo signals from targets simultaneously using interference cancellation techniques. We evaluate the communication performance and sensing estimation across both Rayleigh and measured realistic channels. Additionally, a deep neural network (DNN)-based approach for channel estimation and signal detection in JCAS systems is presented. The DNN outperforms the traditional methods in the bit error rate (BER) versus signal-to-noise ratio (SNR) curves, leveraging its ability to learn complex patterns autonomously. The DNN’s training process fine-tunes the performance based on specific problem characteristics, capturing the nuanced relationships within data and adapting to varying SNR conditions for consistently superior performance compared to the traditional approaches.
- Published
- 2024
- Full Text
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14. Automatic Object Detection in Radargrams of Multi-Antenna GPR Systems Based on Simulation Data for Railway Infrastructure Analysis
- Author
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Lukas Lahnsteiner, David Größbacher, Martin Bürger, and Gerald Zauner
- Subjects
GPR ,object detection ,radargram ,radar ,Technology ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Biology (General) ,QH301-705.5 ,Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
Ground-penetrating radar (GPR) is a non-invasive technology that uses electromagnetic pulses for subsurface exploration. In the railroad sector, it is crucial to assessing soil layers and infrastructure, offering insights into soil stratification and geological features and aiding in identifying subsurface hazards. However, the automation of radargram analysis is impeded by the lack of ground truth—accurate real-world data used to validate machine learning models—thus affecting the deployment of advanced algorithms. This study focuses on generating high-quality simulated data to address the shortage of real-world data in the context of object detection along railroad tracks and presents a fully automated pipeline that includes data generation, algorithm training, and validation using real-world data. By doing so, it paves the way for significantly easing the future task of object detection algorithms in the railway sector. A simulation environment, including the digital twin of a GPR antenna, was developed for artificial data generation. The process involves pre- and post-processing techniques to transform the three-dimensional data from the multichannel GPR system into two-dimensional datasets. This ensures minimal information loss and suitability for established two-dimensional object detection algorithms like the well-known YOLO (You Only Look Once) framework. Validation involved real-world measurements on a track with predefined buried objects. The entire pipeline, encompassing data generation, processing, training, and application, was automated for efficient algorithm testing and implementation. Artificial data show promise for better performance with increased training. Future AI and sensor advancements will enhance subsurface exploration, contributing to safer and more reliable railroad operations.
- Published
- 2024
- Full Text
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15. Survey of Deep Learning-Based Methods for FMCW Radar Odometry and Ego-Localization
- Author
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Marvin Brune, Tobias Meisen, and André Pomp
- Subjects
radar ,SLAM ,autonomous driving ,ego-localization ,odometry ,Technology ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Biology (General) ,QH301-705.5 ,Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
This paper provides an in-depth review of deep learning techniques to address the challenges of odometry and global ego-localization using frequency modulated continuous wave (FMCW) radar sensors. In particular, we focus on the prediction of odometry, which involves the determination of the ego-motion of a system by external sensors, and loop closure detection, which concentrates on the determination of the ego-position typically on an existing map. We initially emphasize the significance of these tasks in the context of radar sensors and underscore the motivations behind them. The subsequent sections delve into the practical implementation of deep learning approaches, strategically designed to effectively address the aforementioned challenges. We primarily focus on spinning and automotive radar configurations within the domain of autonomous driving. Additionally, we introduce publicly available datasets that have been instrumental in addressing these challenges and analyze the importance and struggles of current methods used for radar based odometry and localization. In conclusion, this paper highlights the distinctions between the addressed tasks and other radar perception applications, while also discussing their differences from challenges posed by alternative sensor modalities. The findings contribute to the ongoing discourse on advancing radar sensor capabilities through the application of deep learning methodologies, particularly in the context of enhancing odometry and ego-localization for autonomous driving applications.
- Published
- 2024
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16. Springtime mesoscale convective systems over South China: a historic radar image-based analysis of climatological features, interannual variability, and potential connections with surface aerosol
- Author
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Lijuan Zhang, Tzung-May Fu, Zhiqun Hu, Hongjun Liu, Zhiyong Meng, Leiming Ma, Jianhua Dai, and Feng Zhang
- Subjects
mesoscale convective systems ,radar ,aerosol-cloud-precipitation interactions ,Environmental technology. Sanitary engineering ,TD1-1066 ,Environmental sciences ,GE1-350 ,Science ,Physics ,QC1-999 - Abstract
We objectively analyzed historic radar reflectivity images and diagnosed mature mesoscale convective systems (MCSs) in South China during the spring season (March to May) of 2009–2019. Our goal was to understand the climatological features of mature MCSs, their interannual variations, and potential connections with surface aerosol pollution. Springtime MCSs over South China were most frequently observed in the central and east-coastal parts of Guangdong Province. The mean monthly half-hourly counts of MCSs over South China in March, April, and May were 103 ± 83, 274 ± 298, and 337 ± 225, respectively, with considerable variability from year to year. Approximately 89% of springtime MCSs over South China had a linear or quasi-linear structure, with convective precipitation covering on average 34% of the total precipitating area of each individual MCS, anmied 63% of MCSs consisted of a stratiform precipitation area trailing the convective precipitation. In March, MCSs occurred most frequently mid-day; in April and May, MCSs were most frequent around midnight. From 2013 to 2019, the MCS occurrences in April were significantly lower during years with more aerosol pollution days. This finding potentially supported our previous model study’s finding that elevated anthropogenic aerosol levels may suppress April MCS occurrences in South China via aerosol-cloud-radiation interactions. Further research is required to better understand the intricate relationship between aerosol abundance and MCS activities in this region.
- Published
- 2024
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17. A Comparative Study on Recent Progress of Machine Learning-Based Human Activity Recognition with Radar
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Konstantinos Papadopoulos and Mohieddine Jelali
- Subjects
deep learning ,human activity recognition ,micro-Doppler ,machine learning ,radar ,Technology ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Biology (General) ,QH301-705.5 ,Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
The importance of radar-based human activity recognition has increased significantly over the last two decades in safety and smart surveillance applications due to its superiority in vision-based sensing in the presence of poor environmental conditions like low illumination, increased radiative heat, occlusion, and fog. Increased public sensitivity to privacy protection and the progress of cost-effective manufacturing have led to higher acceptance and distribution of this technology. Deep learning approaches have proven that manual feature extraction that relies heavily on process knowledge can be avoided due to its hierarchical, non-descriptive nature. On the other hand, ML techniques based on manual feature extraction provide a robust, yet empirical-based approach, where the computational effort is comparatively low. This review outlines the basics of classical ML- and DL-based human activity recognition and its advances, taking the recent progress in both categories into account. For every category, state-of-the-art methods are introduced, briefly explained, and their related works summarized. A comparative study is performed to evaluate the performance and computational effort based on a benchmarking dataset to provide a common basis for the assessment of the techniques’ degrees of suitability.
- Published
- 2023
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18. Partition-Based Point Cloud Completion Network with Density Refinement
- Author
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Jianxin Li, Guannan Si, Xinyu Liang, Zhaoliang An, Pengxin Tian, and Fengyu Zhou
- Subjects
convolutional neural networks ,point cloud completion ,gridding ,radar ,geometric density ,Science ,Astrophysics ,QB460-466 ,Physics ,QC1-999 - Abstract
In this paper, we propose a novel method for point cloud complementation called PADPNet. Our approach uses a combination of global and local information to infer missing elements in the point cloud. We achieve this by dividing the input point cloud into uniform local regions, called perceptual fields, which are abstractly understood as special convolution kernels. The set of point clouds in each local region is represented as a feature vector and transformed into N uniform perceptual fields as the input to our transformer model. We also designed a geometric density-aware block to better exploit the inductive bias of the point cloud’s 3D geometric structure. Our method preserves sharp edges and detailed structures that are often lost in voxel-based or point-based approaches. Experimental results demonstrate that our approach outperforms other methods in reducing the ambiguity of output results. Our proposed method has important applications in 3D computer vision and can efficiently recover complete 3D object shapes from missing point clouds.
- Published
- 2023
- Full Text
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19. Dual-Polarization Radar Fingerprints of Precipitation Physics: A Review.
- Author
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Kumjian, Matthew R., Prat, Olivier P., Reimel, Karly J., van Lier-Walqui, Marcus, and Morrison, Hughbert C.
- Subjects
- *
RADAR , *PHYSICS , *RAINFALL , *MICROPHYSICS , *SPACE-based radar , *RADAR meteorology - Abstract
This article reviews how precipitation microphysics processes are observed in dual-polarization radar observations. These so-called "fingerprints" of precipitation processes are observed as vertical gradients in radar observables. Fingerprints of rain processes are first reviewed, followed by processes involving snow and ice. Then, emerging research is introduced, which includes more quantitative analysis of these dual-polarization radar fingerprints to obtain microphysics model parameters and microphysical process rates. New results based on a detailed rain shaft bin microphysical model are presented, and we conclude with an outlook of potentially fruitful future research directions. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
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20. Editorial: Plasmonic metamaterials and electromagnetic devices volume 2
- Author
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Zhen Liao and Kai-Da Xu
- Subjects
electromagnetic devices ,filter ,antenna ,microwave ,radar ,Physics ,QC1-999 - Published
- 2022
- Full Text
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21. A Sector-Matching Probability Hypothesis Density Filter for Radar Multiple Target Tracking
- Author
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Jialin Yang, Defu Jiang, Jin Tao, Yiyue Gao, Xingchen Lu, Yan Han, and Ming Liu
- Subjects
multi-target tracking ,radar ,random finite sets ,sampling time variety ,weak targets ,Technology ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Biology (General) ,QH301-705.5 ,Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
The development of high-tech, dim, small targets, such as drones and cruise missiles, brings great challenges to radar multi-target tracking (MTT), making it necessary to extend the beam dwell time to obtain a high signal-to-noise ratio (SNR). In order to solve the problem of radar sampling time variation exacerbated by extending the beam dwell time when detecting weak targets, a sector-matching (SM) PHD filter is proposed, which combines the actual radar system with a PHD filter and quantifies the relationship between the beam dwell time, the false alarm rate and the detection probability. The proposed filter divides the scanning area into small sectors to obtain actual multi-target measurement times and rederives the prediction and update steps based on the actual sampling time. Furthermore, a state correction step is added before state extraction. Applying the SM structure to the basic Gaussian mixture PHD (GM-PHD) filter and labeled GM-PHD filter, the simulation results demonstrate that the proposed structure can improve the accuracy of multi-weak-target state estimation in the dense clutter and can continuously generate explicit trajectories. The overall real-time performance of the proposed filter is similar to that of the PHD filter.
- Published
- 2023
- Full Text
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22. Drone and Controller Detection and Localization: Trends and Challenges
- Author
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Jawad Yousaf, Huma Zia, Marah Alhalabi, Maha Yaghi, Tasnim Basmaji, Eiman Al Shehhi, Abdalla Gad, Mohammad Alkhedher, and Mohammed Ghazal
- Subjects
Unmanned aerial vehicles (UAVs) ,detection technologies ,radio frequency-based (RF) ,radar ,acoustic ,electro optical ,Technology ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Biology (General) ,QH301-705.5 ,Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
Unmanned aerial vehicles (UAVs) have emerged as a rapidly growing technology seeing unprecedented adoption in various application sectors due to their viability and low cost. However, UAVs have also been used to perform illegal and malicious actions, which have recently increased. This creates a need for technologies capable of detecting, classifying, and deactivating malicious and unauthorized drones. This paper reviews the trends and challenges of the most recent UAV detection methods, i.e., radio frequency-based (RF), radar, acoustic, and electro-optical, and localization methods. Our research covers different kinds of drones with a major focus on multirotors. The paper also highlights the features and limitations of the UAV detection systems and briefly surveys the UAV remote controller detection methods.
- Published
- 2022
- Full Text
- View/download PDF
23. Modified Uncertainty Error Aware Estimation Model for Tracking the Path of Unmanned Aerial Vehicles
- Author
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Rui Fu, Mohammed Abdulhakim Al-Absi, Young-Sil Lee, Ahmed Abdulhakim Al-Absi, and Hoon Jae Lee
- Subjects
drones ,tracking ,UAVs detection ,radar ,RLS ,Technology ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Biology (General) ,QH301-705.5 ,Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
Recently, with the advancement of technology, unmanned aerial vehicles (UAVs) have had a significant impact on our daily lives. UAVs have gained critical importance due to their potential threat. In this study, the problem of UAV tracks were investigated. The first study deals with a particle filter (PF) and a diffusion map with a Kalman filter (DMK). From the experimental analysis, it is found that both PF and DMK are very suitable for drone tracking because the trajectories of drones are highly uncertain in highly dynamic and noisy environments. To address this problem, we introduce a Kalman filter (KFUEA) for drone tracking based on uncertainty and error. The KFUEA uses regularized least squares (RLS) to minimize measurement errors and provides an appropriate balance between confidence in previous estimates and future measurements. The experiment was conducted to evaluate the performance of KFUEA compared to PF and DMK, taking into account the high uncertainty and noisy UAV tracking environment. The KFUEA algorithm achieved an excellent result in the root mean square error (RMSE) compared to the non-parametric filtering algorithms PF and DMK.
- Published
- 2022
- Full Text
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24. The Casio DBC-62.
- Author
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McARTHUR-CHRISTIE, MARK
- Subjects
ADVERTISING agencies ,PLAYGROUNDS ,PHYSICS ,CALCULATORS ,RADAR - Abstract
The article titled "The Casio DBC-62" discusses the Casio DBC-62 databank calculator watch from the 1990s. The watch, which could store 50 sets of 12 character messages and function as a calculator, was popular among school students who used it for exams and classes. However, with the advancement of technology, the watch has become obsolete, as even the cheapest phones can perform its functions and more. Collectors are starting to show interest in the watch, but it is only valued at around £200 in perfect condition. [Extracted from the article]
- Published
- 2024
25. Study of an Atmospheric Refractivity Estimation from a Clutter Using Genetic Algorithm
- Author
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Doyoung Jang, Jongmann Kim, Yong Bae Park, and Hosung Choo
- Subjects
radio propagation ,radar ,optimization algorithms ,clutter images ,Technology ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Biology (General) ,QH301-705.5 ,Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
In this paper, a method for estimating atmospheric refractivity from sea and land clutters is proposed. To estimate the atmospheric refractivity, clutter power spectrums based on an artificial tri-linear model are calculated using an Advanced Refractive Prediction System (AREPS) simulator. Then, the clutter power spectrums are again obtained based on the measured atmospheric refractivity data using the AREPS simulator. In actual operation, this spectrum from measured reflectivity can be replaced with real-time clutter spectrums collected from radars. A cost function for the genetic algorithm (GA) is then defined based on the difference between the two clutter power spectrums to predict the atmospheric refractivity using the artificial tri-linear model. The optimum variables of the tri-linear model are determined at a minimum cost in the GA process. The results demonstrate that atmospheric refractivity can be predicted using the proposed method from the clutter powers.
- Published
- 2022
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26. Design and Experimental Analyses of an Accuracy Verification System for Airborne Target Tracking via Radar Guidance Systems
- Author
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Yingchao Han, Weixiao Meng, and Xiaodong Wang
- Subjects
wireless measurement analysis ,seeker ,radar ,radio frequency data ,test and experiment ,Technology ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Biology (General) ,QH301-705.5 ,Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
A radar guidance system is a core component of a radar-guided air-to-air missile, and its tracking accuracy of airborne targets determines the operational effectiveness of said missile. To verify the tracking accuracy of the radar guidance system against an airborne target under the real flight conditions of the missile, an experimental verification system was implemented in this study. The mechanical, electrical, and bus interfaces of the verification system were examined. A tracking accuracy evaluation model of the seeker was designed based on the data obtained from the experiments using the proposed test method, and the tracking accuracy of the seeker in the typical state was analyzed.
- Published
- 2022
- Full Text
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27. 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
- Author
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Y. Ahajjam, O. Aghzout, J. M. Catala-Civera, F. Peñaranda-Foix, and A. Driouach
- Subjects
Transmitter ,UWB ,Radar ,sensor ,Generator ,SRD ,Physics ,QC1-999 ,Electricity and magnetism ,QC501-766 - Abstract
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.
- Published
- 2019
- Full Text
- View/download PDF
28. Contactless Soil Moisture Mapping Using Inexpensive Frequency-Modulated Continuous Wave RADAR for Agricultural Purposes
- Author
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Rui M. Coutinho, Armando Sousa, Filipe Santos, and Mário Cunha
- Subjects
soil moisture ,RADAR ,FMCW ,non-invasive ,capacitive sensing ,precision agriculture ,Technology ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Biology (General) ,QH301-705.5 ,Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
Soil Moisture (SM) is one of the most critical factors for a crop’s growth, yield, and quality. Although Ground-Penetrating RADAR (GPR) is commonly used in satelite observation to analyze soil moisture, it is not cost-effective for agricultural applications. Automotive RADAR uses the concept of Frequency-Modulated Continuous Wave (FMCW) and is more competitive in terms of price. This paper evaluates the viability of using a cost-effective RADAR as a substitute for GPR for soil moisture content estimation. The research consisted of four experiments, and the results show that the RADAR’s output signal and the soil moisture sensor SEN0193 have a high correlation with values as high as 0.93 when the SM is below 15%. Such results show that the tested sensor (and its cost-effective working principle) are able to determine soil water content (with certain limitations) in a non-intrusive, proximal sensing manner.
- Published
- 2022
- Full Text
- View/download PDF
29. Spatial diversity improvement in frequency-diverse computational imaging with a multi-port antenna
- Author
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The Viet Hoang, Thomas Fromenteze, Muhammad Ali Babar Abbasi, Cyril Decroze, Mohsen Khalily, Vincent Fusco, and Okan Yurduseven
- Subjects
Frequency-diversity ,Computational imaging ,Radar ,Microwaves ,Singular value decomposition ,Physics ,QC1-999 - Abstract
In this paper, we study an additional spatial diversity mechanism added to a cavity-backed frequency-diverse aperture for computational imaging applications at X-band frequencies. It is shown that the dynamic variation of cavity modes achieved by means of a simple, multi-port excitation mechanism can significantly simplify the diversity constraints on the frequency-diversity technique for computational imaging and can substantially improve the fidelity of the reconstructed microwave images. Leveraging the proposed technique, we present that, for the selected number of measurement modes, the condition number of the studied computational imaging problem is improved by 8.5 times in comparison to using the frequency-diversity as the only diversity mechanism. The reconstructed X-band images of various targets, including the letters “Q”, “U” and “B” reflect on this improvement and exhibit a higher reconstruction quality, significantly assisting in the identification of the imaged objects. We also present that the resolution limits of the frequency-diverse computational imaging system synthesized using the proposed multi-port cavity are in excellent agreement with the theoretical resolution limits.
- Published
- 2021
- Full Text
- View/download PDF
30. Modulation Linearization Technique for FM/CW SAR Image Processing Using Range Migration
- Author
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Theodore Grosch and Cyril Okhio
- Subjects
autofocus ,FMCW ,radar ,range migration ,Stolt transform ,nonlinear error ,Technology ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Biology (General) ,QH301-705.5 ,Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
Linear FMCW radar suffers from impairments in range and range rate if there are errors in the modulation rate or phase discontinuities. Often, this is a result of a nonlinearity of the voltage-controlled oscillator that is in the source of the transmit and receive local oscillator. The nonlinearity can be corrected at the source by using a nonlinear control voltage or by processing the received beat frequency. Any signal processing using the later method leads to computation time and energy costs, which can be considerable in some applications. When the range migration algorithm using the Stolt Transform is used for Synthetic Aperture Radar (SAR) image processing, the autofocus linearization technique described here costs nothing in additional hardware or computation time.
- Published
- 2021
- Full Text
- View/download PDF
31. Sampled data spectroscopy (SDS): A new technology for radiation instrumentation
- Author
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Odell, D
- Published
- 1992
32. Realization of High-Gain Low-Sidelobe Wide-Sector Beam Using Inductive Diaphragms Loaded Slotted Ridge Waveguide Antenna Array for Air Detection Applications
- Author
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Tao Su, Jinshan Ding, Yu-Tong Zhao, Jianzhong Chen, Min Bao, Tian Hu, and Liang Li
- Subjects
Beamforming ,Physics ,business.industry ,law.invention ,Antenna array ,Beamwidth ,Optics ,law ,Radar imaging ,Equivalent circuit ,Power dividers and directional couplers ,Electrical and Electronic Engineering ,Radar ,Antenna (radio) ,business - Abstract
This paper presents a high-gain slotted ridge waveguide array antenna (SRWAA) with inductive diaphragms, which can realize a wide-sector beam with a low sidelobe simultaneously. The proposed antenna can cover a wide detection range and avoid interference from other directions. The expected excitation distribution for the antenna array is extracted through a beamforming method. To reduce the influence of the dispersion phenomenon on signal quality, inductive diaphragms are inserted into the sidewall of the ridge waveguide, which is fully analyzed from the point of the equivalent circuit. A cut-off-mode power divider is utilized, which can control the power ratio flexibly. A SRWAA working at 24.125 GHz, including a six-way feeding network, and a 6×24 slot array with the size of 330 mm × 66.8 mm is designed and fabricated. The measured sidelobe level (SLL) and half-power beamwidth (HPBW) in the elevation plane are -19.6 dB and 54.41°, with the counterparts in the azimuth plane -29.8 dB and 3.15°, respectively. The measured peak gain is 22.3 dBi at 24.125 GHz. The measured results are in good agreement with the simulated ones. This work has the potential to be applied in air detection, anti-unmanned aerial vehicles (UAVs), meteorological radar, and imaging radar.
- Published
- 2022
33. Adaptive Mutual Coupling Compensation Method for Airborne STAP Radar With End-Fire Array
- Author
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Yuanyi Xiong and Wenchong Xie
- Subjects
Physics ,Coupling ,law ,Acoustics ,Aerospace Engineering ,Electrical and Electronic Engineering ,Radar ,law.invention ,Compensation (engineering) - Published
- 2022
34. Roll-to-Roll In-Line Implementation of Microwave Free-Space Non-Destructive Evaluation of Conductive Composite Thin Layer Materials
- Author
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Grigorios Koutsoukis, Ivan Alic, Antonios Vavouliotis, Ferry Kienberger, and Kamel Haddadi
- Subjects
vector network analyzer (VNA) ,free-space ,radar ,microwave nondestructive testing (MNDT) ,composites ,prepreg ,Technology ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Biology (General) ,QH301-705.5 ,Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
A free-space microwave nondestructive testing and evaluation module is developed for the low-power, non-ionizing, contactless, and real-time characterization of doped composite thin-film materials in an industrial context. The instrumentation proposed is built up with a handled vector network analyzer interfaced with corrugated horn antennas to measure the near-field complex reflection S11 of planar prepreg composite materials in a roll-to-roll in-line production line. Dedicated modeling and calibrations routines are developed to extract the microwave conductivity from the measured microwave signal. Practical extraction of the radiofrequency (RF) conductivity of thin film prepreg composite materials doped with nano-powders is exemplary shown at the test frequency of 10 GHz.
- Published
- 2021
- Full Text
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35. AMIE (ARM MJO Investigation Experiment): Observations of the Madden-Julian Oscillation for Modeling Studies Science Plan
- Author
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Xie, S
- Published
- 2010
- Full Text
- View/download PDF
36. Enhanced sprint performance analysis in soccer: New insights from a GPS-based tracking system.
- Author
-
Reinhardt, Lars, Schwesig, René, Lauenroth, Andreas, Schulze, Stephan, and Kurz, Eduard
- Subjects
- *
SPRINTING , *OUTDOOR recreation , *SPRINTING training , *SOCCER , *PHYSICAL sciences , *SOCCER players , *GLOBAL Positioning System , *PERFORMANCE evaluation , *VELOCITY - Abstract
The aim of this investigation was to establish the validity of a GPS-based tracking system (Polar Team Pro System, PTPS) for estimating sprint performance and to evaluate additional diagnostic indices derived from the temporal course of the movement velocity. Thirty-four male soccer players (20 ± 4 years) performed a 20 m sprint test measured by timing gates (TG), and while wearing the PTPS. To evaluate the relevance of additional velocity-based parameters to discriminate between faster and slower athletes, the median-split method was applied to the 20-m times. Practical relevance was estimated using standardized mean differences (d) between the subgroups. Differences between the criterion reference (TG) and PTPS for the 10 and 20 m splits did not vary from zero (dt10: -0.01 ± 0.07 s, P = 0.7, d < -0.1; dt20: -0.01 ± 0.08 s, P = 0.4, d < -0.2). Although subgroups revealed large differences in their sprint times (d = -2.5), the average accelerations between 5 and 20 km/h as well as 20 and 25 km/h showed merely small effects (d < 0.5). Consequently, analyses of velocity curves derived from PTPS may help to clarify the occurrence of performance in outdoor sports. Thus, training consequences can be drawn which contribute to the differentiation and individualization of sprint training. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
37. Full physics simulation of terrain‐adaptive 77 GHz automotive radar for early pedestrian detection.
- Author
-
Chipengo, Ushemadzoro
- Subjects
- *
ROAD vehicle radar , *RADAR cross sections , *PEDESTRIAN accidents , *PEDESTRIANS , *DRIVER assistance systems , *RADAR targets , *PHYSICS - Abstract
Fully autonomous vehicles and the need to improve road safety have led to increased demands on the reliability of various advanced driver assistance systems (ADAS). Automotive radar is a key component of ADAS as it adds both safety and comfort features in vehicles. A key challenge in developing automotive radar is demonstrating reliability especially in corner cases. Building and testing radar systems for corner cases is time‐consuming, costly, and impractical. Simulation is the only practical way of investigating the countless possible automotive radar corner cases. An interesting corner case is the reduction of radar returns due to sharp road bends. Specifically, crucial targets with low radar cross sections (RCS) such as pedestrians can become invisible to radar when driving around sharp road bends. In this article, a high fidelity, full physics‐based simulation of a 77 GHz automotive radar scene will be used to investigate this corner case. The dependence of radar returns on the position of an ego vehicle negotiating a sharp bend will be presented. Results from these simulations show a pedestrian disappearing from view at an approaching angle of 60∘ with a degradation of over 40 dB in pedestrian radar returns. Using results from this study, a terrain‐adaptive technique for improving radar target detection capabilities is proposed. This technique is shown to improve pedestrian radar returns by over 26 dB. Improved radar returns can help in early detection of pedestrians and other relevant targets. Early target detection can help reduce accidents while potentially saving pedestrian lives. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
38. Evaluating the sustainable traffic flow operational features of an exclusive spur dike U-turn lane design.
- Author
-
Shao, Yang, Han, Xueyan, Wu, Huan, Shan, Huimin, Yang, Shaowei, and Claudel, Christian G.
- Subjects
- *
TRAFFIC flow , *TRAFFIC conflicts , *TRAFFIC congestion , *TIME travel , *CONTINUUM mechanics - Abstract
The traditional U-turn design has significantly improved traffic operations for relieving traffic congestion. However, the U-turn diversion and merge segments still cause traffic conflicts and delays. In this paper, an exclusive spur dike U-turn lane (ESUL) is proposed with the aim of addressing the disadvantages of the traditional U-turn design. ESUL provides a separate U-turn lane to diverge, decelerate, U-turn, accelerate and merge without interacting with through traffic. The effectiveness of ESUL is demonstrated through a field data investigation, simulation and analysis with VISSIM software. The proposed design is evaluated in terms of three parameters: travel time, delay and number of stops. Compared to the traditional U-turn design, ESUL can reduce travel time by 29.15%, delay by 66.70% and the number of stops by 100% at most. The results showed that ESUL has better performance than the traditional U-turn design and could be implemented to reduce traffic congestion and the potential hazards caused by U-turn maneuvers. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
39. A Fuzzy Comprehensive CS-SVR Model-based health status evaluation of radar.
- Author
-
Yang, Yifei, Zhang, Maohui, and Dai, Yuewei
- Subjects
- *
RADAR , *EVALUATION - Abstract
The purpose of Fuzzy Comprehensive CS-SVR Model (FCCS-SVR) is to evaluate and monitor the health status of a radar equipment and then keep its safe operation. Due to reasons such as few samples, slow changes and the nonlinear structure of data of fault monitoring signal, the health status evaluation of a radar system is quite difficult. By establishing the evaluation index system of a radar, the combination of AHP method and Entropy weight method is studied in this paper. In order to evaluate the value of health status, several optimization algorithms including PSO, GA, BA and CS are used for optimizing the parameters of SVR model. Meanwhile, in order to avoid the problem that the system is at the edge of the state, a radar health assessment method based on the combination of Fuzzy Comprehensive Evaluation and Cuckoo Search-Support Vector Regression (CS-SVR), which is named as Fuzzy Comprehensive CS-SVR (FCCS-SVR), is further proposed. The result of case analysis reflects that the state evaluation of the radar system is realized. The system performance analysis shows that the use of FCCS-SVR evaluation method provides a high recognition rate and can accurately assess the health status of the radar system. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
40. Augmented Depolarizing Scatterer Based on Resonant Elements for Polarimetric Radar Calibration
- Author
-
Etienne Perret, Zeshan Ali, Laboratoire de Conception et d'Intégration des Systèmes (LCIS), Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), and Université Grenoble Alpes (UGA)-Université Grenoble Alpes (UGA)
- Subjects
Physics ,Radar cross-section ,scatterer ,business.industry ,Polarimetry ,020206 networking & telecommunications ,02 engineering and technology ,Polarization (waves) ,law.invention ,Chipless RFID ,Planar ,Optics ,[INFO.INFO-TS]Computer Science [cs]/Signal and Image Processing ,law ,Calibration technique ,radar cross section ,0202 electrical engineering, electronic engineering, information engineering ,Calibration ,Electrical and Electronic Engineering ,Antenna (radio) ,Radar ,business ,polarimetric radar - Abstract
International audience; A 3-in-1 depolarizing circular scatterer for the polarimetric radar calibration is proposed in this paper. The proposed scatterer is low cost, compact, planar circuit, and well suited for the radar operating in a compact range, for example, chipless RFID technology. By the virtue of its circular shape, the rear side of the proposed scatterer acts as a metallic disk with strong co polarization backscattered signals. The front side is composed of eight resonant dipoles which make it nondepolarizing and depolarizing scatterers at the inclination of 0° and 45°, respectively. The features of proposed circular scatterer are tested as reference calibration objects for single antenna based polarimetric radar calibration techniques. Two test objects are utilized: a dihedral tilted at 45° and a depolarizing multi resonant planar structure commonly called chipless RFID tag. The performance of proposed circular scatterer is also compared with the standard reference calibration objects: a metallic disk and a dihedral tilted at 22.5°. The performance of proposed circular scatterer is comparable to the standard reference calibration objects for the calibration techniques (namely Type 1 and Type 2). The proposed scatterer is potentially tolerant of displacement up to 1 cm and misalignment equals 2°.
- Published
- 2022
41. Near-Field Orthogonal Beam Scan by Phased Arrays of Antennas With Active Analog Beamformer for Maximum NF-RCS in Target Detection
- Author
-
Hsi-Tseng Chou
- Subjects
Physics ,business.industry ,HFSS ,Scattering ,Phase (waves) ,Near and far field ,law.invention ,Antenna array ,Optics ,law ,Singular value decomposition ,Physics::Accelerator Physics ,Electrical and Electronic Engineering ,Radar ,Antenna (radio) ,business - Abstract
Near-field radar cross-section (NF-RCS) of a target depends on antennas’ radiation and can be maximized by adjusting the radiation patterns. It is justified by the power return ratio and can be computed by a comparison method. A theoretical foundation of operational mechanism for phased arrays of antennas is presented to produce conformal radiations for NF-RCS enhancement. The target’s scattering coefficients are extracted from operating the antenna array’s digital phase shifters to steer the resulting beams in this work. The scattering matrix is then analyzed by the singular value decomposition (SVD) to determine the antennas’ excitations for maximum NF-RCS with estimation stability. It results in orthogonal beams for the two-way radiations of antenna arrays to interpret the scattering mechanisms. The feasibility is validated by HFSS full-wave simulations and experimental measurement data.
- Published
- 2022
42. Performance Comparison of Planar, Cylindrical, and Polygonalized Phased Arrays for Surveillance and Ubiquitous Radar
- Author
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Anna Stumme, W. Mark Dorsey, and Dan P. Scholnik
- Subjects
Physics ,Planar ,law ,Acoustics ,Performance comparison ,Aerospace Engineering ,Electrical and Electronic Engineering ,Radar ,law.invention - Published
- 2022
43. High‐speed target imaging for vortex electromagnetic wave radar
- Author
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Wen-Xuan Xie, Yong-Zhong Zhu, He-Feng Zhao, Yi-Jun Chen, and Yu-Ang Zhou
- Subjects
Physics ,law ,Acoustics ,Telecommunication ,TK5101-6720 ,Electrical and Electronic Engineering ,Radar ,Electromagnetic radiation ,law.invention ,Vortex - Abstract
Vortex electromagnetic waves (VEMWs) carrying orbital angular momentum (OAM) are promising to benefit the higher degree of freedom for inverse synthetic aperture radar (ISAR) imaging on account of their helical wavefront. For high‐speed targets, the ‘stop and go’ hypothesis is no longer valid. Thus, the intrapulse movement of the target will cause the broadening and shift of the one‐dimensional range profile and the blurring of the OAM eigenvalues coupling azimuth. This contribution proposes a high‐speed target imaging method for the VEMW ISAR. First, an OAM‐based ISAR imaging model for high‐speed targets is derived and the echo characteristics are analysed. Subsequently, in order to effectively estimate the ratio of the echo to correct the imaging result, an estimation method that takes into account the calculation speed and accuracy is proposed. On this basis, the target velocity distribution obtained under multiple echoes is analysed to improve the accuracy of the results. Finally, the range profile and azimuthal profile are reconstructed. Compared with the existing vortex electromagnetic imaging algorithm, the proposed method can effectively eliminate the influence of high‐speed motion on the range and azimuth profile. This work provides suggestions for the development of EM vortex ISAR imaging technology.
- Published
- 2022
44. Using a stacked-autoencoder neural network model to estimate sea state bias for a radar altimeter.
- Author
-
Miao, Xiangying, Miao, Hongli, Jia, Yongjun, and Guo, Yingting
- Subjects
- *
ALTIMETERS , *NEURAL circuitry , *OCEAN waves , *RESIDUAL stresses , *STRAINS & stresses (Mechanics) - Abstract
This paper constructed a stacked-autoencoder neural network model (SAE model) to estimate sea state bias (SSB) based on radar altimeter data. Six cycles of the geophysical data record (GDR) from Jason-1/2 radar altimeters were used as a training dataset, and the other 2 cycles of the GDR from Jason-1/2 were used for testing. The inputs to this SAE model include the significant wave height (SWH), wind speed (U), sea surface height (SSH), backscatter coefficient (σ0) and automatic gain control (AGC), and the model outputs the SSB. The model includes one input layer, three hidden layers and one output layer. The SSBs in the GDR of Jason-1/2 were obtained from a nonparametric model based on the SWH and U as input variables; thus, the model has high accuracy but low efficiency. The SSBs in the GDR of HY-2A were computed using a four-parameter parametric model that uses the SWH and U as input variables; therefore, this model’s computational speed is high but its accuracy is low. Thus, we used the HY-2A radar altimeter as an unseen validation dataset to evaluate the performance of the SAE model. Then, we analyzed the contrasting results of these methods, including the differences in the SSB, explained variance, residual error and operational efficiency. The results demonstrate not only that the accuracy of the SAE model is superior to that of the conventional parametric model but also that its operational efficiency is better than that of the nonparametric model. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
45. Range Aliasing Elimination for FMICW Radar With Uniform Sampling Bursts and Poisson Disk Inter-Burst Delays
- Author
-
Gang Li, Boyuan Dong, Kunpeng Wang, and Meiya Duan
- Subjects
Physics ,law ,Poisson disk ,Acoustics ,Range (statistics) ,Sampling (statistics) ,Electrical and Electronic Engineering ,Aliasing (computing) ,Radar ,Instrumentation ,law.invention - Published
- 2022
46. Simulation of Pol-SAR Imaging and Data Analysis of Mini-RF Observation From the Lunar Surface
- Author
-
Ya-Qiu Jin and Niutao Liu
- Subjects
Physics ,Scattering ,Surface finish ,Geodesy ,law.invention ,law ,Radar imaging ,Surface roughness ,General Earth and Planetary Sciences ,Degree of polarization ,Electrical and Electronic Engineering ,Radar ,Digital elevation model ,Circular polarization - Abstract
High circular polarization ratio (CPR) characteristics were found in permanently shaded regions (PSRs) near the lunar poles. High CPR was regarded as a water ice index. The compact-polarimetric (CP) miniature radio frequency (Mini-RF) radar transmits left-circularly polarized signals and receives horizontally polarized (SHL ) and vertically-polarized (SVL ) echoes from the lunar surface. Statistics of the CPR data show its relations with the relative phase (δ ) between SHL and SVL and the degree of polarization (m) but few interpretations were provided. The average CPR data reach the maximum and minimum at δ =± 90°, respectively. As m becomes very small, the CPR approaches 1. It has been found that CPR is also affected by surface roughness and incidence angle of radar waves. The CPR is now expressed in CP mode to explain the Mini-RF observation. Full-polarimetric radar echoes and CP parameters of the lunar surface are numerically simulated using the bidirectional analytic ray-tracing method. Single-bounce and multiple-bounce scattering components are included in the simulation. Radar images of the lunar crater are simulated with the digital elevation model (DEM) data. The H-α decomposition derived from the full-polarimetric simulation is presented to analyze δ and m. Simulated radar images with different surface roughness are analyzed statistically to study the functional dependences of δ , m, and CPR on incidence angle and roughness. Relationships among δ , m, and CPR are used to analyze the effects of incidence angle, roughness, TiO₂ , and rock abundance on the scattering components. The CPR, m, and δ of PSR craters of different ages are compared with those of nonpolar craters. The results indicate that the CPR, m, and δ are unlikely to be unambiguous evidence of water ice.
- Published
- 2022
47. Radar Interferometric Phase Errors Induced by Faraday Rotation
- Author
-
Franz J. Meyer and Simon Zwieback
- Subjects
Physics ,Phase (waves) ,Polarimetry ,Magnitude (mathematics) ,Deformation (meteorology) ,Geodesy ,law.invention ,symbols.namesake ,Interferometry ,law ,Faraday effect ,Interferometric synthetic aperture radar ,symbols ,General Earth and Planetary Sciences ,Electrical and Electronic Engineering ,Radar - Abstract
Ionospheric Faraday rotation distorts satellite radar observations of the Earth's surface. While its impact on radiometric observables is well understood, the errors in repeat-pass interferometric synthetic aperture radar (InSAR) observations and hence in deformation analysis are largely unknown. Because Faraday rotation cannot rigorously be compensated for in nonquad-pol systems, it is imperative to determine the magnitude and nature of the deformation errors. Focusing on distributed targets at L-band, we assess the errors for a range of land covers using airborne observations with simulated Faraday rotation. We find that the deformation error may reach 2 mm in the copol channels over a solar cycle. It can exceed 5 mm for intense solar maxima. The cross-pol channel is more susceptible to severe errors. We identify the leakage of polarimetric phase contributions into the interferometric phase as a dominant error source. The polarimetric scattering characteristics induce a systematic dependence of the Faraday-induced deformation errors on land cover and topography. Also, their temporal characteristics, with pronounced seasonal and quasi-decadal variability, predispose these systematic errors to be misinterpreted as deformation. While the relatively small magnitude of 1-2 mm is of limited concern in many applications, the persistence on semiannual to multiannual time scales compels attention when long-term deformation is to be estimated with millimetric accuracy. Phase errors induced by uncompensated Faraday rotation constitute a nonnegligible source of bias in interferometric deformation measurements.
- Published
- 2022
48. Simple Derivation of the Nonuniform Beam Filling (NUBF) Bias Formula in Spaceborne Doppler Radar Measurements
- Author
-
Kenji Nakamura and Non Member
- Subjects
Physics ,Discretization ,Doppler radar ,Geotechnical Engineering and Engineering Geology ,Square (algebra) ,Computational physics ,law.invention ,Radiation pattern ,Distribution (mathematics) ,dBZ ,law ,Electrical and Electronic Engineering ,Radar ,Physics::Atmospheric and Oceanic Physics ,Beam (structure) - Abstract
The non-uniform beam filling bias in Doppler velocity measurements from a spaceborne precipitation radar is investigated. A simple derivation of the already-known formula that relates the bias to the along-track gradient of measured radar reflectivity in dBZ is shown. From the formula, the uncertainty of bias correction due to discretization is discussed. The error is shown to be proportional to the square of the spacing for discretization, and is related to the third moment of the distribution of the radar reflectivity convolved with the antenna pattern. The effectiveness of averaging is also shown from a simulation.
- Published
- 2022
49. An Up-Sampled Particle Filter Fusion Technique and Its Application in Synthetic Aperture Radar Imaging
- Author
-
Mark Yeary, Russell H. Kenney, Jay W. McDaniel, Brian M. Sun, and Hjalti H. Sigmarsson
- Subjects
Physics ,Fusion ,business.industry ,Synthetic aperture radar imaging ,kalman filters ,particle filters ,ComputingMethodologies_IMAGEPROCESSINGANDCOMPUTERVISION ,TK5101-6720 ,Electric apparatus and materials. Electric circuits. Electric networks ,Optics ,Telecommunication ,inertial navigation ,iterative methods ,business ,Particle filter ,Global positioning system ,TK452-454.4 ,Physics::Atmospheric and Oceanic Physics ,radar - Abstract
Global positioning system (GPS) and inertial measurement units (IMUs) are often combined to produce navigation systems for airborne imaging platforms. The current state-of-the-art radar technology allows for radars to pulse at very high rates. GPS and IMU update rates are not fast enough to accurately report the platform position for each radar pulse. Independent GPS and IMUs cannot provide positional accuracy for long term stability. Traditional techniques, such as the Kalman and particle filter, are used to fuse GPS and IMU measurements. The Kalman filter excels for linear and Gaussian systems whereas the particle filter excels at non-linear and non-Gaussian systems. Sensor fusion techniques are used to help correct for IMU errors and provide the positional accuracy required for synthetic aperture radar (SAR) imaging applications. However, SAR requires the fusion algorithms to provide faster update rates. This paper explores the use of an up-sampled particle filter (UPF) for SAR to provide highly accurate position estimates at sampling frequencies comparable to radar pulse rates and overcome the limitations of standard interpolation techniques. This up-sampled particle filter is proven through simulations and instrumentation with a NovAtel GPS and IMU. The UPF technique allows for the GPS/IMU sampling rate to be different from the radar pulse repetition frequency (PRF) while providing accurate position solutions for each radar pulse capable of compensating for the phase history required for focusing a SAR image. The algorithms are instrumented in a SAR system and the position estimates are further validated and demonstrated through captured SAR images.
- Published
- 2022
50. Modeling of Surface Roughness With an Anisotropic Power-Law Spectrum and Its Applications to Radar Backscattering From Soil Surfaces
- Author
-
Kun-Shan Chen, Ying Yang, and Xiuyi Zhao
- Subjects
Physics ,Scattering ,Context (language use) ,Surface finish ,Power law ,law.invention ,Computational physics ,law ,Surface roughness ,General Earth and Planetary Sciences ,Electrical and Electronic Engineering ,Radar ,Anisotropy ,Scaling ,Physics::Atmospheric and Oceanic Physics - Abstract
We present a generalized power-law roughness spectrum to account for the spatial anisotropy effects on the radar scattering of a rough surface, where both the correlation anisotropy and the scaling anisotropy are accounted for. The spatial anisotropy is essential to correctly interpret the radar scattering from an agriculture field where both plow and sow are practiced. We investigate the dependence of the backscattering coefficient on the correlation anisotropy and the scaling anisotropy through a model simulation. A drastic change in backscattering strength is observed due to the anisotropy. The correlation anisotropy and the scaling anisotropy generate similar backscattering angular behavior, implying that in the context of spatial anisotropy, merely using correlation length in scattering modeling is insufficient. Equivalently, the correlation length retrieved from the backscattering coefficients perhaps is not unique. Fair use of the generalized anisotropic power-law roughness spectrum in conjunction with the scattering model is illustrated by comparing the backscattering coefficients with experimental measurements. However, the anisotropy complicates the roughness description in terms of surface parameters retrieval because we can generate similar backscattering angular patterns by combining different correlation anisotropy and scaling anisotropy. When the soil moisture is of primary interest, a more suitable radar observation geometry to minimize the spatial anisotropy influence is desirable.
- Published
- 2022
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