Browsing by Author "Inggs, Mike"

Now showing 1 - 6 of 6
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    A spaceborne synthetic aperture radar data processor
    (1991) Welsh, Simon; Inggs, Mike
    This thesis is concerned with the design and implementation of a Synthetic Aperture Radar (SAR) data processor. The implementation of the processing is based on a standard sequential approach to the problem and employs commonly used algorithms. The processing was done using the C language running on an IBM Compatible Personal Computer. The raw data processed was that obtained from the Shuttle Imaging Radar B (SIRB) and was supplied by the Jet Propulsion Laboratories (JPL) in California. The basic functions performed by the software include range and azimuth processing, which involve the match filtering of reference functions with the raw data. Compensation for the effects of being a spaceborne SAR were also implemented, which involved compensation for the effect of planet rotation and radar height. Images processed by JPL of the same area were also available, which allowed for direct comparisons between the outputs of the two SAR processors. The images produced were passed through a number of filters, to improve the image quality, and resulted in favourable comparisons to the JPL generated images. The actual images are included in the later sections of the thesis.
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    Design and implementation of a non-contact microwave level measument instrument
    (2010) Ward, Jonathan Michael; Inggs, Mike
    This dissertation describes the design and implementation of a microwave level measurement instrument for sensing the level of a substance inside a tank up to 10 m in height. A radar transceiver had to be designed to replace an acoustic sensor on an existing 4-20 mA loop powered ultrasonic instrument and had to be compatible with its on-board acoustic signal processing hardware. Specifications are developed for a pulsed radar architecture operating at 5.8 GHz with a bandwidth around 1 GHz and at a repetition frequency of 3.58 MHz.
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    Mission Planning Tool for space debris studies with the MeerKAT radar
    (2018) Dhondea, Ashiv Rao; Inggs, Mike
    The Radar Remote Sensing Group at the University of Cape Town is currently investigating the feasibility of building an active radar system employing the MeerKAT radio telescope as receiver for space debris detection, tracking and imaging. This dissertation details the development of a Mission Planning Tool (MPT) to perform sensor scheduling and to support the performance prediction and analysis of the proposed MeerKAT radar. The MeerKAT radar project proposal is made in the context of developing space surveillance and tracking capacities in South Africa. The MeerKAT radar is intended to operate bistatically, with a transmitter located in Bredasdorp (South Africa) and the MeerKAT radio telescope as receiver. The system design and radar signal processing design are currently under development in another RRSG project. Before the feasibility study can progress further, a Mission Planning Tool has been developed to assist in scheduling the bistatic radar to perform an observation experiment, to calculate the predicted radar measurements and errors as well as to estimate the orbit of the observed object. This report documents how these objectives were met by the MPT software developed in Python. Given a LEO space object of interest’s Two Line Element set, the MPT performs orbit propagation with an SGP4 method to generate trajectories for radar performance evaluation. The MPT determines the most opportune epoch (the longest possible target dwell-time within the antenna beam) for executing an observation experiment with the MeerKAT radar. Space objects investigated in this project were found to be have spent between 4.5 s to 12.8 s in the transmitter’s illuminating beam. The MeerKAT radio telescopes are tasked to act as receivers at the appropriate antenna pointing and time period. Based on the bistatic geometry of the specific observation experiment, the MPT predicts the signal-to-noise ratio at the radar receiver as well as the bistatic range, bistatic Doppler shift and look angles. The integrated SNR values for the experiments considered in this report ranged from 11 dB to 68 dB. From the coherently integrated SNR, the MPT estimates the radar measurement errors. Finally, the orbit determination module was engineered with two radar measurement schemes: a bistatic range and Doppler shift scheme and a bistatic range and look angles scheme. Monte Carlo experiments were run to evaluate the tracking performance resulting from the two tracking schemes. The Gauss-Newton tracking filter based on the first scheme fails to converge whereas it produces accurate results with the second scheme (estimated position error of 2 m and velocity error of 0.08 m/s). It is therefore recommended to opt for the bistatic range and look angles measurement scheme in future work. Since the current MeerKAT radar design cannot create look angles measurements, an observables estimation scheme was adopted. It was found that this scheme produced accurate elevation and azimuth angles with an estimation error of ±0.04◦ . Since the quoted values result from a preliminary design of the MeerKAT radar, they are bound to change in the final design. Therefore the MPT should be loaded with the final radar design’s parameters and run again to produce useful results. This reports shows that, with the help of the Mission Planning Tool developed in this project, the proposed MeerKAT radar can be feasibly scheduled to observe and track space objects in the LEO regime based on a single target pass.
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    Speckle reduction in SAR imagery
    (1995) Gebhardt, Mark William Dewdney; Inggs, Mike
    Synthetic Aperture Radar (SAR) is a popular tool for airborne and space-borne remote sensing. Inherent to SAR imagery is a type of multiplicative noise known as speckle. There are a number of different approaches which may be taken in order to reduce the amount of speckle noise in SAR imagery. One of the approaches is termed post image formation processing and this is the main concern of this thesis. Background theory relevant to the speckle reduction problem is presented. The physical processes which lead to the formation of speckle are investigated in order to understand the nature of speckle noise. Various statistical properties of speckle noise in different types of SAR images are presented. These include Probability Distribution Functions as well as means and standard deviations. Speckle is considered as a multiplicative noise and a general model is discussed. The last section of this chapter deals with the various approaches to speckle reduction. Chapter three contains a review of the literature pertaining to speckle reduction. Multiple look methods are covered briefly and then the various classes of post image formation processing are reviewed. A number of non-adaptive, adaptive and segmentation-based techniques are reviewed. Other classes of technique which are reviewed include Morphological filtering, Homomorphic processing and Transform domain methods. From this review, insights can be gained as to the advantages and disadvantages of various methods. A number of filtering algorithms which are either promising, or are representative of a class of techniques, are chosen for implementation and analysis.
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    Time and Frequency Transfer in a Coherent Multistatic Radar using a White Rabbit Network
    (2021) Lewis, Simon A C; Inggs, Mike
    Networks of coherent multistatic radars require accurate and stable time and frequency transfer (TFT) for range and Doppler estimation. TFT techniques based on global navigation satellite systems (GNSS), have been favoured for several reasons, such as enabling node mobility through wireless operation, geospatial referencing, and atomic clock level time and frequency stability. However, such systems are liable to GNSS-denial, where the GNSS carrier is temporarily or permanently removed. A denial-resilient system should consider alternative TFT techniques, such as the White Rabbit (WR) project. WR is an Ethernet based protocol, that is able to synchronise thousands of nodes on a fibre-optic based network with sub-nanosecond accuracy and picoseconds of jitter. This thesis evaluates WR as the TFT network for a coherent multistatic pulse-Doppler radar – NeXtRAD. To test the hypothesis that WR is suitable for TFT in a coherent multistatic radar, the time and frequency performance of a WR network was evaluated under laboratory conditions, comparing the results against a network of multi-channel GPS-disciplined oscillators (GPSDO). A WR-disciplined oscillator (WRDO) is introduced, which has the short-term stability of an ovenised crystal (OCXO), and long-term stability of the WR network. The radar references were measured using a dual mixer time difference technique (DMTD), which allows the phase to be measured with femtosecond level resolution. All references achieved the stringent time and frequency requirements for short-term coherent bistatic operation, however the GPSDOs and WRDOs had the best short-term frequency stability. The GPSDOs had the highest amount of long-term phase drift, with a peak-peak time error of 9.6 ns, whilst the WRDOs were typically stable to within 0.4 ns, but encountered transient phase excursions to 1.5 ns. The TFT networks were then used on the NeXtRAD radar, where a lighthouse, Roman Rock, was used as a static target to evaluate the time and frequency performance of the references on a real system. The results conform well to the laboratory measurements, and therefore, WR can be used for TFT in coherent radar.
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    Using GPS bistatic signal for land and ocean remote sensing in South Africa
    (2007) Phaladi, Shikoane Given; Inggs, Mike
    This project discusses the basic principles and theory of this new technology, and concentrates on reflection points and Fresnel zones. The CPS receivers are placed at different coastal regions within South Africa, and the simulation of the reflection points and Fresnel zones are observed as the CPS satellites pass over South Africa. The East London area was chosen as the location to place the receiver throughout my analysis.