Radar Test Research Articles

The Three Dimension First-Order Symplectic Partitioned Runge-Kutta Scheme Simulation for GPR Wave Propagation in Pavement Structure

Numerical simulation of three-layer layered electromagnetic waves is key problem for nondestructive testing of ground penetrating radar (GPR) pavement. In this paper, the difference iterative scheme of three-dimensional first-order symplectic partitioned Rung-Kutta is derived, which is applied to pavement detection of ground penetrating radar by using Higdon ABC boundary condition. Incident waves are considered as line sources. The accuracy and efficiency of the proposed algorithm are verified by the traditional 3D-FDTD algorithm. The results indicate that the accuracy and efficiency between the two methods are consistent. Unlike the traditional 3D-FDTD algorithm, the CPU time of the proposed method is reduced by 30%. The diseases location of the pavement structure is directly reflected by the numerical simulation result of the proposed method. This provides a three-dimensional symplectic partitioned Rung-Kutta algorithm, which can be applied to the forward simulation of GPR. It provides a three-dimensional symplectic partitioned Rung-Kutta algorithm, which can be applied to the forward simulation of GPR. The accurate electromagnetic response information of the target can be obtained by the proposed method.

Generalised polarimetric whitening filter for polarimetric MIMO radar detection

The polarimetric multiple-input multiple-output (MIMO) radar utilises both the polarisation and spatial diversities, thus the generalised likelihood ratio test (GLRT) of the polarimetric MIMO radar exhibits better detection performance than the GLRT of the MIMO radar when the secondary data set is large enough. However, the secondary data set is often not enough in reality. In this instance, the good detection performance of the GLRT of polarimetric MIMO radar cannot be guaranteed any more. In this study, the authors propose three kinds of generalised polarimetric whitening filters (GPWFs) to improve the detection performance of polarimetric MIMO radar in the limited secondary data environment. They first present the signal models and the test statistics for the three GPWFs. Then they analyse the detection performance of the three GPWFs by simulation, and find the second GPWF performs the best. They further compare the detection performance of the second GPWF with those of the GLRT and non-coherent integration (NCI) detector. Simulation results show that the proposed second GPWF outperforms the GLRT and NCI in the limited secondary data environment.

Prediction of remaining service life of pavement using an optimized support vector machine (case study of Semnan–Firuzkuh road)

ABSTRACTAccurate prediction of the remaining service life (RSL) of pavement is essential for the design and construction of roads, mobility planning, transportation modeling as well as road management systems. However, the expensive measurement equipment and interference with the traffic flow during the tests are reported as the challenges of the assessment of RSL of pavement. This paper presents a novel prediction model for RSL of road pavement using support vector regression (SVR) optimized by particle filter to overcome the challenges. In the proposed model, temperature of the asphalt surface and the pavement thickness (including asphalt, base and sub-base layers) are considered as inputs. For validation of the model, results of heavy falling weight deflectometer (HWD) and ground-penetrating radar (GPR) tests in a 42-km section of the Semnan–Firuzkuh road including 147 data points were used. The results are compared with support vector machine (SVM), artificial neural network (ANN) and multi-layered perceptron (MLP) models. The results show the superiority of the proposed model with a correlation coefficient index equal to 95%.

Георадарная съемка проблемных объектов

Георадарная съемка проблемных объектов

Practical Multichannel SAR Imaging in the Maritime Environment

The U.S. Naval Research Laboratory (NRL) recently developed an X-band airborne multichannel synthetic aperture radar (MSAR) test bed system that consists of 32 along-track phase centers. This system was deployed in September 2014 and again in October 2015 to perform extensive and systematic data collections on a variety of land and maritime scenes under different environmental conditions. This paper presents a detailed experimental analysis of imaging in the maritime domain using data captured by the NRL MSAR system. After presenting some of the important details of our NRL MSAR system, we demonstrate velocity-based imaging of a variety of moving backscatter sources including ships and shoaling ocean waves. Our analysis is based on the velocity SAR (VSAR) technique, which was originally conceived by Friedlander and Porat. Practical application of this algorithm in the maritime domain requires a number of pre- and postprocessing stages, which are described here in detail. Our results are then benchmarked against the traditional along-track interferometry, where it is demonstrated that VSAR processing is better able to correctly compensate motion-induced distortion.

Reflection waveforms occurring in bistatic radar testing of columns and tree trunks

Ground-penetrating radar is a non-destructive inspection device which is not often applied to cylindrical media. In this paper, we extend our previous analyses of monostatic GPR waveforms to two bistatic radar configurations for cylindrical objects: 1) Single-offset radar system, where two antennas are simultaneously rotating around the cylinder, 2) multi-offset radar system, where only a receiving antenna is rotating around it. Analyses were performed through numerical experiments with gprMax2D, straight-ray analytical solutions, laboratory and real case studies. The complex real case studies highlighted the benefit of combining bistatic and monostatic radar data acquisitions to better resolve unknown internal structures.

EcoSAR

This article contains information on EcoSAR. EcoSAR is the advanced airborne polar metric and single pass interferometric P-band SAR instruments under development at the NASA Goddard Space Flight Center, through NASA's instrument Incubator Program (IIP). EcoSar will provide two and three-dimensional fine scale measurements of terrestrial ecosystem structure and biomass onboard the NASA P3 aircraft. These measurements directly support science requirements for the study of the carbon cycle and its relationship to climate change. To evaluate plant growth on earth from an airborne platform, both construction of the radar and subsequent testing of the radar using advanced radar test equipment to help develop and improve the radar system was necessary. This article describes the development, testing, and deployment of the EcoSAR system.

New Method for Testing the Grouting Compactness in Pre-Stressed Concrete Girder

Background: The post-tensioned pre-stressed concrete girder is widely used in modern bridge construction. Grouting compactness has a great influence on the safety, reliability and durability of pre-stressed concrete girders. So, it is important to test the grouting compactness of the pre-stressed girder to ensure the construction quality and meet the design requirements. However, there are some defects in the existing method for testing the grouting quality of post-tensioned pre-stressed concrete girders. Therefore, a new method should be invented. Methods: In this paper, the recent research status and patents on grouting compactness testing are summarized, and the principles of grouting quality testing methods (ultrasonic testing method, impact-echo method, radiographic testing method, endoscope testing method, infrared radiometry method, and ground penetrating radar testing method) that are commonly used are compared and analyzed. Results: Based on the advantages, disadvantages and applicability of these testing methods, by refining the current patents relating to grouting compactness testing, new intelligent testing equipment is integrated, and new method is proposed. Conclusion: This new method is more efficient and accurate and it has good applicability in engineering. Keywords: Post-tensioning method, pre-stressed concrete girder, grouting compactness, testing, new method, duct grouting.

Design and Control of a Quadruple-Input Double-Output Coherent Radar Test Platform Composed of Test & Measurement Equipment and Custom Hardware

A radar test platform composed of commercial off-the-shelf test and measurement equipment and custom hardware has been built. This platform, which enables production of dual-channel coherent radar transmitting signals with a bandwidth up to 500MHz, and reception of four parallel channels of RF injection signals or echoes, can simulate various types of radar emitters or to simulate the multiple modes of operation for a single type radar. A software is also programmed with C++ language to control the waveforms, frequencies, phases, time delays and all other aspects of the test platform’s operation at all stages. At last, an application example is given when the platform is used for ISAR imaging verification.

Design and Analysis of Transmitter Charge Switch Assembly Load on Weather Radar Test Platform

This paper provides a new method for designing the load of transmitters switch components on provincial radar test platform. Based on the calculation of the specific parameters related to the actual charge switch components, the load-related data model is obtained, the simulation is carried out, and the results are consistent with the actual test results. Through the theoretical numerical analysis of the load of the charging switch components of the transmitter device in the new generation of weather radar maintenance test platform, radar maintenance personnel at all levels can deepen the thorough understanding of the CINRAD/SA transmitter and have some enlightenment and improvement on the maintenance guarantee ability of the new generation of weather radar.

Comprehensive investigation of leakage problems for concrete gravity dams with penetrating cracks based on detection and monitoring data: A case study

The leakage amount is an important indicator evaluating the seepage behavior of a dam. Due to the complex behavior, crack development judgment and leakage behavior identification for concrete gravity dams remain a challenging task. The paper is concerned with comprehensive investigation of leakage problems for concrete gravity dams with penetrating cracks. A case study on Shimantan Reservoir Dam was taken to examine the utilization of the comprehensive investigation method. Deficiency investigations were undertaken to identify the nature and sources of defects responsible for the serious leakage. Based on the information acquired from field visual inspections and ground-penetrating radar tests, it is apparent that several transverse cracks penetrate the dam crest and propagate downward into the dam body. The results of the remedial grouting, X-ray diffraction analyses and water injection tests reflect the appearance of penetrating leakage paths in the dam body. Subsequently, 2 behavior models including the special hydrostatic-seasonal-time model and the inverse analysis model were conducted to distinguish the contribution of penetrating cracks to leakage amount. The special hydrostatic-seasonal-time model was modified to address the influence of leakage flow in real microcracks in concrete dams based on the Navier–Stokes equation. The result shows that the proposed models provide an acceptable accuracy in analyzing leakage monitoring data for gravity dams with penetrating cracks. Leakage flow in penetrating cracks plays a dominant role in the dam seepage field. The execution flow in this paper could be readily employed in investigations of similar problems of concrete dams.

The Application of PXI VSA in Radar Testing System

A radar testing system that takes PXI VSA modules as the main component is presented. The methods of spectrum parameters testing, waveform envelope parameters of pulse modulation signal testing and the peak power testing are analyzed. The software structure and testing flow are expounded in detail. The feasibility of the overall design is discussed in this paper.

Aircraft-sized anechoic chambers for electronic warfare, radar and other electromagnetic engineering evaluation

ABSTRACTThis paper considers capabilities and benefits of aircraft-sized radio/radar frequency anechoic chambers for Test and Evaluation (T&E) of Electronic Warfare (EW), radar and other electromagnetics aspects of air and ground platforms. There are few such chambers worldwide. Initially developed to reduce costs, timescales and risks associated with open-air range flight testing of EW systems, their utility has expanded to most areas of platforms’ electromagnetics’ T&E. A key feature is the ability to conduct T&E of nationally sensitive equipment and systems, fully installed on platforms, in absolute privacy. Chambers’ capabilities and uses are described, with emphasis on key infrastructure and instrumentation. Non-EW uses are identified and selected topics elaborated. Operation and maintenance are discussed, based on experiential knowledge from international use and the authors’ 30 years’ involvement with BAE Systems’ EW Test Facility. A view is provided of trends and challenges whose resolution could further increase chamber utility. National affordability challenges also suggest utility expansion to support continuing moves, from expensive and difficult to repeat flight test and operational evaluation trials, towards an affordability-driven optimal balance between modelling and simulation, and real-world testing of platforms.

Assessment of the density and moisture content of asphalt mixtures of road pavements

Distresses on asphalt pavements are associated to the traffic and moisture both in asphalt and granular layers. The traffic on road pavements is responsible by the occurrence of cracks that promote the pavement failure. The quality of the asphalt mixes, measured by its density, is an important factor to ensure the integrity of the pavements. The water in pavement surface decreases the driving comfort and reduces the asphalt-aggregate bond leading to the degradation of the asphalt materials. Thus, this paper uses Ground Penetrating Radar (GPR) tests to assess density and moisture content on asphalt mix slabs. Six asphalt mixes were produced in laboratory with the same aggregate gradation and asphalt type, varying the binder content (4.0, 5.0 and 6.0%) and the air-void content (from 3.7% up to 16.9%). For the assessment of the moisture content, each mix was tested with 5, 10, 20 and 40% of the air-void volume filled with water. The effect of the water on GPR results was performed after the sprinkling of the water and 24h after the water application. Results show that the density of the asphalt mixes can be well predicted by the Complex Refractive Index Model while the presence of water is not easy to identify due to the connectivity of the air-voids inside the asphalt mixes.

Seismic risk assessment of Trani\u2019s Cathedral bell tower in Apulia, Italy

The present paper deals with the evaluation of the seismic vulnerability of slender historical buildings; these structures, in fact, may manifest a high risk with respect to seismic actions as usually they have been designed to resist to gravitational loads only, and are characterized by a high flexibility. To evaluate this behavior, the bell tower of the Trani’s Cathedral is investigated. The tower is 57 m tall and is characterized by an unusual building typology, i.e., the walls are composed of a concrete core coupled with external masonry stones. The dynamic parameters and the mechanical properties of the tower have been evaluated on the basis of an extensive experimental campaign that made use of ambient vibration tests and ground penetrating radar tests. Such data have been utilized to calibrate a numerical model of the examined tower. A linear static analysis, a dynamic analysis and a nonlinear static analysis have been carried out on such model to evaluate the displacement capacity of the tower and the seismic risk assessment in accordance with the Italian guidelines.

The nonlinear radar testing on the reliability of the objects’ identification

The nonlinear radar testing using a single wideband simulator of the laying device is considered. It is shown that the simulator on the basis of the flat two-armed spiral antennas with semiconductor diode in the load has a thermal sensitivity to electromagnetic field. The energy dissipation of the probe signal leads to deformation of the current-voltage characteristics (CVC) of the diode composed of the simulator. Parameter $\gamma$ is introduced as the degree of closeness to the equilibrium state of the diode. It characterizes the degree of CVC deformation during sensing. According to the experimental data normalized approximating function (NAF) depending on the parameter $\gamma$ is obtained. The phenomenon of a lens identification attribute inversion using NAF is investigated. It consists in changing the ratio between the levels of second and third harmonics response signal to the opposite value. The acquisition of unmasking properties of the structure "metal-oxide-metal" by simulator is identified. The maximum frequency distribution of the unmasking sign inversion occurrence depending on the normalized voltage value of operating point displacement of the diode composed of the simulator is received. It is suggested to capture the unmasking sign inversion of the simulator to judge the reliability of embedded devices detection and identification by the ability of nonlinear radar.

A Combination of GPR Survey and Laboratory Rock Tests for Evaluating an Ornamental Stone Deposit in a Quarry Bench

The paper examines methods of assessing the critical fractures and quality of an ornamental stone deposit. Fracture status was evaluated by an in-situ Ground Penetrating Radar (GPR) test. The resulting 3D GPR model allowed exploration of the extension, shape, and orientation of the detected fractures surfaces. It also identified a rock stratum with a noticeably lower load of critical fractures compared to the other strata. Physico-mechanical properties were investigated by laboratory tests allowing classification of the deposit into quality categories, which provided a promising correlation with the GPR survey results.

Determining the Optimal Frequency of Ground Penetrating Radar for Detecting Voids in Pavements

PURPOSES : The objective of this study is to determine the optimal frequency of ground penetrating radar (GPR) testing for detecting the voids under the pavement. METHODS : In order to determine the optimal frequency of GPR testing for void detection, a full-scale test section was constructed to simulate the actual size of voids under the pavement. Voids of various sizes were created by inserting styrofoam at varying depths under the pavement. Subsequently, 250-, 500-, and 800-MHz ground-coupled GPR testing was conducted in the test section and the resulting GPR signals were recorded. The change in the amplitude of these signals was evaluated by varying the GPR frequency, void size, and void depth. The optimum frequency was determined from the amplitude of the signals. RESULTS: The capacity of GPR to detect voids under the pavement was evaluated by using three different ground-coupled GPR frequencies. In the case of the B-scan GPR data, a parabolic shape occurred in the vicinity of the voids. The maximum GPR amplitude in the A-scan data was used to quantitatively determine the void-detection capacity. CONCLUSIONS: The 250-MHz GPR testing enabled the detection of 10 out of 12 simulated voids, whereas the 500-MHz testing allowed the detection of only five. Furthermore, the amplitude of GPR detection associated with 250-MHz testing is significantly higher than that of 500-MHz testing. This indicates that 250-MHz GPR testing is well-suited for the detection of voids located at depths ranging from 0.5~2.0 m. Testing at frequencies lower than 250 MHz is recommended for void detection at depths greater than 2 m.

Utility detection and positioning on the urban site Sense-City using Ground-Penetrating Radar systems

This paper presents the design of a novel Ground-Penetrating Radar (GPR) test site that has been integrated into the mini-city demonstrator Sense-City located at University Paris-Est (France). This test site provides several sources of measurement interest expressed by the presence of a multilayered soil with significant dielectric contrasts, and various dielectric pipes and blades buried at various depths in trenches filled with a backfill soil different from the natural soil. This paper presents experimental Bscans associated with the pipe zone acquired by three different GPR systems at frequencies ranging from 300MHz to 1.5GHz. The interpretation and comparison of the raw Bscans have allowed to characterize the dielectric properties of the soil layers, and to detect the hyperbola signatures of the buried pipes. The results of this study will help to guide future developments on polarization, operating frequency and signal processing to extract parameters (orientation, dielectric characteristics, position and size) associated with pipes.

Aerial LiDAR analysis in geomorphological mapping and geochronological determination of surficial deposits in the Sodankylä region, northern Finland

Geomorphological mapping based on an aerial light detection and ranging (LiDAR)-derived digital elevation model, field observations, ground penetrating radar measurements and test pit surveys was carried out in a glaciogenic environment in Sodankylä, central Finnish Lapland. The mapping area covered about 370 km2, with the LiDAR data having a pixel size of 2 m × 2 m and vertical resolution 0.3 m. The geomorphology of the area consists of large till-covered hills, ground moraine plains, glaciofluvial sand and gravel deposits composed of esker systems and related delta and outwash formations of the Weichselian cold stages, followed by pro-glacial glaciolacustric and post-glacial lacustric and fluvial sand/silt deposits. Furthermore, large areas in topographical depressions are covered by Holocene mires. The benefits of LiDAR data compared to traditional aerial-photo-based interpretation were in more detailed identification of surface deposits and more precise edging of the morphologies. This reflected more accurately the true ground surface in areas of dense vegetation. As an example, based on the LiDAR mapping it was possible to distinguish several till-covered delta and sandur deposits which based on OSL dating date back to the Early Weichselian stadial (74–89 ka). The results of the mapping project have been collated and published in a Quaternary geological map of the Sodankylä region.