Browsing by Author "Inggs, Michael R"

Now showing 1 - 9 of 9
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    Open Access
    Calibration of airborne L-, X-, and P-band fully polarimetric SAR systems using various corner reflectors
    (2017) Algafsh, Abdullah; Inggs, Michael R; Mishra, Amit
    Synthetic aperture radar polarimetry is one of the current developments in the field of remote sensing, due to the ability of delivering more information on the physical properties of the surface. It is known as the science of acquiring, processing and analysing the polarisation state in an electromagnetic field. The increase of information with respect to scalar radar comes at a price, not only for the high cost of building the radar system and processing the data or increasing the complexity of the design, but also for the amount of effort needed to calibrate the data. Synthetic aperture radar polarimetric calibration is an essential pre- processing stage for the correction of distortion interference which is caused by the system inaccuracies as well as atmospheric effects. Our goal, with this thesis, is to use multiple passive point targets to establish the difference between fully, and compact polarimetric synthetic aperture radar systems on both calibration, and the effects of penetration. First, we detail the selection, design, manufacture, and deployment of different passive point targets in the field for acquiring X- and P-band synthetic aperture radar data in the Netherlands. We started by presenting the selection and design of multiple passive point targets. These were a combination of classic trihedral and dihedral corner reflectors, as well as gridded trihedral and dihedral corner reflectors. Additionally, we detailed the construction of these corner reflectors. The number of constructed corner reflector totalled sixteen, where six are for X-band and six for P-band, as well as four gridded corner reflectors for X-band. Finally, we present the deployment of the corner reflectors at three different sites with carefully surveyed and oriented positions. a Then, we present the calibration of three different fully polarimetric synthetic aperture radar sensors. The first sensor is the L-band synthetic aperture radar sensor and we acquired data using two square trihedral corner reflectors. The calibration includes an evaluation of two crosstalk methods, which are the Quegan and the Ainsworth methods. The results showed that the crosstalk parameters for the Quegan method are all between -17 dB to -21 dB before calibration, while there is a small improvement in the range of 3 dB after calibration. While the Ainsworth method shows around -20 dB before calibration, and around -40 dB after calibration. Moreover, the phase, channel imbalance, and radiometric calibration were corrected using the two corner reflectors. Furthermore, the other two synthetic aperture radar sensors are X- and P-band synthetic aperture radar sensors, and we acquired polarimetric data using our sixteen corner reflectors. The calibration includes the crosstalk estimation, and correction using the Ainsworth method and the results showed the crosstalk parameters before calibration for X-band are around -23 dB, and they are around -43 dB after calibration, while crosstalk parameters before calibration for P-band are around -10 dB, and they are around -30 dB after calibration. The calibration also includes the phase, channel imbalance, and radiometric calibration, as well as geometric correction and signal noise ration measurement, for both X- and P-band. Next, we present the performance of gridded trihedral and dihedral corner reflectors using an X-band synthetic aperture radar system. The results showed both gridded trihedral and dihedral reflectors are perfect targets for correcting the amplitude compared to classical corner reflectors; however, it is not possible to use the gridded reflectors to correct the phase as we need a return from two channels to have a zero-phase difference between the polarisation channels H - V. Furthermore, we detail the compact polarimetric calibration over three com- pact polarimetric modes using a square trihedral corner reflector for the X-band dataset. The results showed no change in the π/mode while a 90ᵒ phase bias showed in the CTLR mode. Finally, the DCP mode showed a 64.43° phase difference, and it was corrected to have a zero phase, and the channel imbalance was very high at 45.92, the channels were adjusted to have a channel imbalance of 1. b Finally, an experiment to measure the penetration and reduction of P-band signal from a synthetic aperture radar system was performed using two triangular trihedral corner reflectors. Both of them have 1.5 m inner leg dimensions. The first triangular trihedral corner reflector was deployed in a deciduous grove of trees, while the other one was deployed a 10 m distance away on a grass covered field. After system calibration based on the reflector in the clear, the results showed a reduction of 0.6 dB in the HH channel, with 2.28 dB in the W channel. The larger attenuation at W is attributable to the vertical structure of the trees. Additionally, we measured the polarimetric degradation of the triangular trihedral corner reflector immersed in vegetation (trees). Further, after calibration, the co-polarisation phase difference is zero degrees for the triangular corner reflector which was outside the trees, and 62.85ᵒ for the corner reflector inside the trees. The designed and fabricated X- and P-band SAR can work operationally with the calibration parameters obtained in this thesis. The data generated through the calibration experiments can be exploited for further applications.
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    Open Access
    De-interleaving of Radar Pulses for EW Receivers with an ELINT Application
    (2017) Aldossary, Mohammad; Inggs, Michael R
    De-interleaving is a critical function in Electronic Warfare (EW) that has not received much attention in the literature regarding on-line Electronic Intelligence (ELINT) application. In ELINT, on-line analysis is important in order to allow for efficient data collection and for support of operational decisions. This dissertation proposed a de-interleaving solution for use with ELINT/Electronic-Support-Measures (ESM) receivers for purposes of ELINT with on-line application. The proposed solution does not require complex integration with existing EW systems or modifications to their sub-systems. Before proposing the solution, on-line de-interleaving algorithms were surveyed. Density-based spatial clustering of applications with noise (DBSCAN) is a clustering algorithm that has not been used before in de-interleaving; in this dissertation, it has proved to be effective. DBSCAN was thus selected as a component of the proposed de-interleaving solution due to its advantages over other surveyed algorithms. The proposed solution relies primarily on the parameters of Angle of Arrival (AOA), Radio Frequency (RF), and Time of Arrival (TOA). The time parameter was utilized in resolving RF agility. The solution is a system that is composed of different building blocks. The solution handles complex radar environments that include agility in RF, Pulse Width (PW), and Pulse Repetition Interval (PRI).
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    Open Access
    A domain specific language for facilitating automatic parallelization and placement of SDR patterns into heterogeneous computing architectures
    (2017) Mohapi, Lerato Jerfree; Winberg, Simon; Inggs, Michael R
    This thesis presents a domain-specific language (DSL) for software defined radio (SDR) which is referred to as OptiSDR. The main objective of OptiSDR is to facilitate the development and deployment of SDR applications into heterogeneous computing architectures (HCAs). As HCAs are becoming mainstream in SDR applications such as radar, radio astronomy, and telecommunications, parallel programming and optimization processes are also becoming cumbersome, complex, and time-consuming for SDR experts. Therefore, the OptiSDR DSL and its compiler framework were developed to alleviate these parallelization and optimization processes together with developing execution models for DSP and dataflow models of computation suitable for SDR-specific computations. The OptiSDR target HCAs are composed of graphics processing units (GPUs), multi-core central processing units (MCPUs), and field programmable gate arrays (FPGAs). The methodology used to implement the OptiSDR DSL involved an extensive review process of existing SDR tools and the extent to which they address the complexities associated with parallel programming and optimizing SDR applications for execution in HCAs. From this review process, it was discovered that, while HCAs are used to accelerate many SDR computations, there is a shortage of intuitive parallel programming frameworks that efficiently utilize the HCAs' computing resources for achieving adequate performance for SDR applications. There were, however, some very good general-purpose parallel programming frameworks identied in the literature review, including Python based tools such as NumbaPro and Copperhead, as well as the prevailing Delite embedded DSL compiler framework for heterogeneous targets. The Delite embedded DSL compiler framework motivated and powered the OptiSDR compiler development in that, it provides four main compiler development capabilities that are desired in OptiSDR: 1) Generic data parallel executable patterns; 2) Execution semantics for heterogeneous MCPU-GPU run-time; 3) Abstract syntax creation using intermediate representations (IR) nodes; and 4) Extensibility for defining new syntax for other domains. The OptiSDR DSL design processes using this Delite framework involved designing the new structured parallel patterns for DSP algorithms (e.g. FIR, FFT, convolution, correlation, etc.), dataflow models of computation (MoC), parallel loop optimizations (tiling and space splitting), and optimal memory access patterns. Advanced task and data parallel patterns were applied in the OptiSDR dataflow MoCs, which are especially suitable for SDR computations where FPGA-based realtime data acquisition systems feed data into multi-GPUs for implementation of parallel DSP algorithms. Furthermore, the research methodology involved an evaluation process that was used to determine the OptiSDR language's expressive power, efficiency, performance, accuracy, and ease of use in SDR applications, such as radar pulse compression and radio frequency sweeping algorithms. The results include measurements of performance and accuracy, productivity versus performance, and real-time processing speeds and accuracy. The performance of some of the regularly used modules, such as FFT-based Hilbert and cross-correlation was found to be very high, with computations speeds ranging from 70.0 GFLOPS to 72.6 GFLOPS, and speedups of up to 80× compared to sequential C/C++ programs and 50× for Matlab's parallel loops. Accuracy was favourable in most cases favourable. For instance, OptiSDR Octave-like DSP instantiations were found to be accurate, with L2 norm forward-errors ranging from 10⁻¹³ to 10⁻¹⁶for smaller and bigger SDR programs respectively. It can therefore be concluded from the analysis in this thesis that the objectives, which include alleviating the complexities in parallel programming and optimizing SDR applications for execution in HCAs, were met. Moreover, the following hypothesis was validated, namely: "It is possible to design a DSL to facilitate the development of SDR applications and their deployment on HCAs without significant degradation of software performance, and with possible improvement in the automatically emitted low-level source code quality.". It was validated by; 1) Defining the OptiSDR attributes such as parallel DSP patterns and dataflow MoCs; 2) Providing parameterizable SDR modules with automatic parallelization and optimization for performance and accuracy; and 3) Presenting a set of intuitive validation constructs for accuracy testing using root-mean square error, and functional verification of DSP using two-dimensional graphics plotting for radar and real-time spectral analysis plots.
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    Open Access
    Investigating the use of interval algebra to schedule mechanically steered multistatic radars
    (2015) Focke, Richard Wilhelm; Inggs, Michael R; De Villiers, J P
    The findings presented in this thesis support the hypothesis that Interval Algebra (IA), as a temporal reasoning language, should perform scheduling of sensor dwells effciently and effectively. Scheduling of multistatic radars was identified as a promising research area, as it builds upon prior research into monostatic and bistatic radars in South Africa. The hypothesis can be validated by answering three research questions. Can IA allow a multistatic radar system to make more multistatic measurements of targets? Can IA perform as well as established multisensor scheduling techniques in terms of computational requirements? Is it possible to enhance the performance of IA by making use of parallel processing architectures? Answering the first two research questions required selecting a comparison algorithm that is already used extensively in scheduling. The Greedy Randomised Adaptive Search Procedure (GRASP) was selected as it represents two of the biggest groupings of existing scheduling algorithms. Furthermore, greedy optimisations are often preferred as they converge to optimal solutions quicker. Two scheduling scenarios were devised which made use of a binary mechanically steered surveillance radar network. One environment made use of a very simplistic model of the information fusion system, the other implemented all the details rigorously. The first environment was used to compare IA to GRASP, while the second tested a nimble IA scheduler. For both these environments Monte-Carlo simulations were used to test random target locations and motion. A novel IA algorithm that makes use of reduced point algebra was generated that allowed execution time to be reduced. Another, simpler novel contribution was an IA algorithm that ensured that radar tasks are only added to the IA network when required. Using these two techniques it was possible for IA to meet both the performance and execution time of GRASP, as allows for a richer set of constraints than required to perform multistatic scheduling. The Nimble IA Scheduler is a novel contribution which solves the realistic requirement of handling fast-moving and accelerating targets, and provides a small performance increase for the surveillance system. Answering the last research question required implementing IA on a parallel processing architecture. General-Purpose Graphical Processing Units (GP-GPUs) were selected since no published research made use these architectures and they should be well suited to solving constraint satisfaction problems. A novel parallel IA path consistency algorithm was generated in OpenCL building upon parallel versions found in the literature for super-computers. Monte-Carlo simulations were run where both the serial and parallel versions were used to solve path consistency for randomly generated IA networks. The results for the GP-GPU identified that for large networks there was speed-up of between two to three times for consistent networks under three conditions. Firstly, the IA network must be sufficiently large to warrant copying the data to the GP-GPU. Secondly, the IA network must have a percentage of known constraints between 25% and 75%. Thirdly, the average number of IA operators should be less than 9.8. Thus, IA can provide equivalent performance to GRASP if the constraints are reduced. Given problems that require a richer set of constraints, these can easily be handled using IA. Nimble IA scheduling can provide a means to increase the multistatic measurements made and reduce those that are missed due to prediction inaccuracies. IA path consistency can also be used on GP-GPUs but only provides speed-ups under specific conditions.
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    Open Access
    Parameters affecting interferometric coherence and implications for long-term operational monitoring of mining-induced surface deformation
    (2013) Engelbrecht, Jeanine; Inggs, Michael R
    Surface deformation due to underground mining poses risks to health and safety as well as infrastructure and the environment. Consequently, the need for long-term operational monitoring systems exists. Traditional field-based measurements are point-based meaning that the full extent of deforming areas is poorly understood. Field-based techniques are also labour intensive if large areas are to be monitored on a regular basis. To overcome these limitations, this investigation considered traditional and advanced differential radar interferometry techniques for their ability to monitor large areas over time, remotely. An area known to be experiencing mining induced surface deformation was used as test case. The agricultural nature of the area implied that signal decorrelation effects were expected. Consequently, four sources of data, captured at three wavelengths by earth-orbiting satellites were obtained. This provided the opportunity to investigate different phase decorrelation effects on data from standard imaging platforms using real-world deformation phenomenon as test-case. The data were processed using standard dInSAR and polInSAR techniques. The deformation measurement results together with an analysis of parameters most detrimental to long-term monitoring were presented. The results revealed that, contrary to the hypothesis, polInSAR techniques did not provide an enhanced ability to monitor surface deformation compared to dInSAR techniques. Although significant improvements in coherence values were obtained, the spatial heterogeneity of phase measurements could not be improved. Consequently, polInSAR could not overcome ecorrelation associated with vegetation cover and evolving land surfaces. However, polarimetric information could be used to assess the scattering behaviour of the surface, thereby guiding the definition of optimal sensor configuration for long-term monitoring. Despite temporal and geometric decorrelation, the results presented demonstrated that mining-induced deformation could be measured and monitored using dInSAR techniques. Large areas could be monitored remotely and the areal extent of deforming areas could be assessed, effectively overcoming the limitations of field-based techniques. Consequently, guidelines for the optimal sensor configuration and image acquisition strategy for long-term operational monitoring of mining-induced surface deformation were provided.
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    Open Access
    Software simulation of synthetic aperture radar
    (1997) Golda, Peter John; Inggs, Michael R
    The purpose of this report is to set out the results of the development of SAR simulation software. The aim of the thesis was to develop such software so that it provides the necessary functionality but is still flexible and simple to use. It addition it must be developed such that it may be compiled and run on as many platforms as possible and future functionality may be added with ease. All this in order to enable other RRSG members to obtain known simulated SAR data for the purpose of testing SAR processing algorithms.
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    Open Access
    Synchronising coherent networked radar using low-cost GPS-disciplined oscillators
    (2019) Sandenbergh, Jacobus S; Inggs, Michael R
    This text evaluates the feasibility of synchronising coherent, pulsed-Doppler, networked, radars with carrier frequencies of a few gigahertz and moderate bandwidths of tens of megahertz across short baselines of a few kilometres using low-cost quartz GPSDOs based on one-way GPS time transfer. It further assesses the use of line-of-sight (LOS) phase compensation, where the direct sidelobe breakthrough is used as the phase reference, to improve the GPS-disciplined oscillator (GPSDO) synchronised bistatic Doppler performance. Coherent bistatic, multistatic, and networked radars require accurate time, frequency, and phase synchronisation. Global positioning system (GPS) synchronisation is precise, low-cost, passive and covert, and appears well-suited to synchronise networked radar. However, very few published examples exist. An imperfectly synchronised bistatic transmitter-receiver is modelled. Measures and plots are developed enabling the rapid selection of appropriate synchronisation technologies. Three low-cost, open, versatile, and extensible, quartz-based GPSDOs are designed and calibrated at zero-baselines. These GPSDOs are uniquely capable of acquiring phase-lock four times faster than conventional phase-locked loops (PLLs) and a new time synchronisation mechanism enables low-jitter sub-10 ns oneway GPS time synchronisation. In collaboration with University College London, UK, the 2.4 GHz coherent pulsed-Doppler networked radar, called NetRAD, is synchronised using the University of Cape Town developed GPSDOs. This resulted in the first published example of pulsed-Doppler phase synchronisation using GPS. A tri-static experiment is set up in Simon’s Bay, South Africa, with a maximum baseline of 2.3 km. The Roman Rock lighthouse was used as a static target to simultaneously assess the range, frequency, phase, and Doppler performance of the monostatic, bistatic, and LOS phase corrected bistatic returns. The real-world results compare well to that predicted by the earlier developed bistatic model and zero-baseline calibrations. GPS timing limits the radar bandwidth to less than 37.5 MHz when it is required to synchronise to within the range resolution. Low-cost quartz GPSDOs offer adequate frequency synchronisation to ensure a target radial velocity accuracy of better than 1 km/h and frequency drift of less than the Doppler resolution over integration periods of one second or less. LOS phase compensation, when used in combination with low-cost GPSDOs, results in near monostatic pulsed-Doppler performance with a subclutter visibility improvement of about 30 dB.
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    Synthetic aperture radar image simulator for interferometry
    (2001) Wray, Lisa Shannon; Inggs, Michael R; Wilkinson, Andrew J
    An interferometric synthetic aperture radar (SAR) simulator was created for the purposes of experimenting with and demonstration of the interferometric process, mission planning and radar image interpretation. The simulation method employs image statistics and terrain geometry to form a synthetic image and requires inputs of a digital elevation model (DEM), flight path, description, radar parameters, a terrain classification map and temporal decorrelation factors. Output images include the following images: radar cross section, power, total coherence, temporal cohernece factor, geometrical coherence factor, absolute phase, interferograms and flattened interferograms.
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    System design of the MeerKAT L - band 3D radar for monitoring near earth objects
    (2017) Agaba, Doreen; Inggs, Michael R
    This thesis investigates the current knowledge of small space debris (diameter less than 10 cm) and potentially hazardous asteroids (PHA) by the use of radar systems. It clearly identifies the challenges involved in detecting and tracking of small space debris and PHAs. The most significant challenges include: difficulty in tracking small space debris due to orbital instability and reduced radar cross-section (RCS), errors in some existing data sets, the lack of dedicated or contributing instruments in the Southern Hemisphere, and the large cost involved in building a high-performance radar for this purpose. This thesis investigates the cooperative use of the KAT-7 (7 antennas) and MeerKAT (64 antennas) radio telescope receivers in a radar system to improve monitoring of small debris and PHAs was investigated using theory and simulations, as a cost-effective solution. Parameters for a low cost and high-performance radar were chosen, based on the receiver digital back-end. Data from such radars will be used to add to existing catalogues thereby creating a constantly updated database of near Earth objects and bridging the data gap that is currently being filled by mathematical models. Based on literature and system requirements, quasi-monostatic, bistatic, multistatic, single input multiple output (SIMO) radar configurations were proposed for radio telescope arrays in detecting, tracking and imaging small space debris in the low Earth orbit (LEO) and PHAs. The maximum dwell time possible for the radar geometry was found to be 30 seconds, with coherent integration limitations of 2 ms and 121 ms for accelerating and non-accelerating targets, respectively. The multistatic and SIMO radar configurations showed sufficient detection (SNR 13 dB) for small debris and quasi-monostatic configuration for PHAs. Radar detection, tracking and imaging (ISAR) simulations were compared to theory and ambiguities in range and Doppler were compensated for. The main contribution made by this work is a system design for a high performance, cost effective 3D radar that uses the KAT-7 and MeerKAT radio telescope receivers in a commensal manner. Comparing theory and simulations, the SNR improvement, dwell time increase, tracking and imaging capabilities, for small debris and PHAs compared to existing assets, was illustrated. Since the MeerKAT radio telescope is a precursor for the SKA Africa, extrapolating the capabilities of the MeerKAT radar to the SKA radar implies that it would be the most sensitive and high performing contributor to space situational awareness, upon its completion. From this feasibility study, the MeerKAT 3D distributed radar will be able to detect debris of diameter less than 10 cm at altitudes between 700 km to 900 km, and PHAs, with a range resolution of 15 m, a minimum SNR of 14 dB for 152 pulses for a coherent integration time of 2.02 ms. The target range (derived from the two way delay), velocity (from Doppler frequency) and direction will be measured within an accuracy of: 2.116 m, 15.519 m/s, 0.083° (single antenna), respectively. The range, velocity accuracies and SNR affect orbit prediction accuracy by 0.021 minutes for orbit period and 0.0057° for orbit inclination. The multistatic radar was found to be the most suitable and computationally efficient configuration compared to the bistatic and SIMO configurations, and beamforming should be implemented as required by specific target geometry.