The use of pulse-compression thermography for detecting defects in paintings

Interest in the conservation of paintings grows year by year. Their periodic inspection is essential for their conservation over the time. Thermographic non-destructive inspection is one technique useful for paintings, but it is essential to be able to detect buried defects while minimising the level of thermal stimulus. This paper describes a pulse-compression infrared thermography technique whereby defect detection is optimized while minimising the rise in temperature. To accomplish this task, LED lamps driven by a coded waveform based on a linear frequency modulated chirp signal have been used on paintings on both a wooden panel and a canvas layer. These specimens contained artificially fabricated defects. Although the physical condition of each painting was different, the experimental results show that the proposed signal processing procedure is able to detect defects using a low temperature contrast

Quasi-Optical Modelling of Telescope Systems for Planck and STEAMR

This thesis is concerned with the high-frequency quasi-optical modelling of telescope systems, with special attention paid to the Planck satellite, but further work is also performed on the Stratosphere-Troposphere Exchange And climate Monitor Radiome- ter (STEAMR) and the Far Infrared Instrument (FIRI). The primary work surrounds the modelling of far sidelobe (FSL) patterns of the Planck telescope, with a view to replicating features seen in some of the difference maps made by the 857-GHz channel of Planck's High Frequency Instrument (HFI). This is done using a variety of techniques in a number of software packages. The General Reector Antenna Software Package (GRASP9) is used for accurate characterisation of the FSLs using two analysis methods: Physical Optics (PO), and Geometrical Optics (GO) with the Geometrical Theory of Diffraction (GTD). This is then compared against two simplified paraxial lens models of the telescope, namely the Projected-Aperture (PA) technique and Gaussian Beam Mode Analysis (GBMA). PA is performed by Fresnel integration of fields from source to sky, while GBM requires decomposition of a field into a set of Gauss-Laguerre modes which are propagated from source to sky using a ray matrix formalism. The motivation for analysing the Planck FSL structure is to test the assumption that features in the difference map are a result of manufacturing imperfections in the detector horns. To test this hypothesis a number of altered horn geometries are modelled using the NUI Maynooth Experimental Physics departments in-house waveguide mode-matching soft- ware called SCATTER, and these are then used in the analysis of the telescope system. Further use of SCATTER is illustrated in work on ultra-Gaussian horns for STEAMR, and here it is tested against commercial waveguide modelling software Microwave Wizard (uWW). Further modelling is performed for the Cardiff test-bed of the Planck telescope simulator, which was used for qualification of the Planck HFI ight horns pre-launch. Here we test the hypothesis that manufacturing imperfections could be missed if the effects on beam pattern were imperceptible to measurement. This is done using GRASP9, as is the modelling of FIRI, a multi-beam spectral/spatial interferometer which will hopefully break current constraints on angular resolution obtainable at infra-red wavelengths. In general, this thesis aims to provide insight into the modelling of quasi-optical telescope systems, with particular emphasis on multi-moded systems, providing useful information for future data analysis by the Planck project team

Quasi-Optical Modelling of Telescope Systems for Planck and STEAMR

This thesis is concerned with the high-frequency quasi-optical modelling of telescope systems, with special attention paid to the Planck satellite, but further work is also performed on the Stratosphere-Troposphere Exchange And climate Monitor Radiome- ter (STEAMR) and the Far Infrared Instrument (FIRI). The primary work surrounds the modelling of far sidelobe (FSL) patterns of the Planck telescope, with a view to replicating features seen in some of the difference maps made by the 857-GHz channel of Planck's High Frequency Instrument (HFI). This is done using a variety of techniques in a number of software packages. The General Reector Antenna Software Package (GRASP9) is used for accurate characterisation of the FSLs using two analysis methods: Physical Optics (PO), and Geometrical Optics (GO) with the Geometrical Theory of Diffraction (GTD). This is then compared against two simplified paraxial lens models of the telescope, namely the Projected-Aperture (PA) technique and Gaussian Beam Mode Analysis (GBMA). PA is performed by Fresnel integration of fields from source to sky, while GBM requires decomposition of a field into a set of Gauss-Laguerre modes which are propagated from source to sky using a ray matrix formalism. The motivation for analysing the Planck FSL structure is to test the assumption that features in the difference map are a result of manufacturing imperfections in the detector horns. To test this hypothesis a number of altered horn geometries are modelled using the NUI Maynooth Experimental Physics departments in-house waveguide mode-matching soft- ware called SCATTER, and these are then used in the analysis of the telescope system. Further use of SCATTER is illustrated in work on ultra-Gaussian horns for STEAMR, and here it is tested against commercial waveguide modelling software Microwave Wizard (uWW). Further modelling is performed for the Cardiff test-bed of the Planck telescope simulator, which was used for qualification of the Planck HFI ight horns pre-launch. Here we test the hypothesis that manufacturing imperfections could be missed if the effects on beam pattern were imperceptible to measurement. This is done using GRASP9, as is the modelling of FIRI, a multi-beam spectral/spatial interferometer which will hopefully break current constraints on angular resolution obtainable at infra-red wavelengths. In general, this thesis aims to provide insight into the modelling of quasi-optical telescope systems, with particular emphasis on multi-moded systems, providing useful information for future data analysis by the Planck project team

The Design of a Low-Cost Traffic Calming Radar - Development of a radar solution intended to demonstrate proof of concept

This study aimed to develop a radar solution that would aid the traffic calming efforts of the CSIR business campus. The Institute of Transportation Engineers defined traffic calming as "The combination of mainly physical measures that reduce the negative effects of motor vehicle use." Radar-based solutions have been proven to help reduce the speeds of motorists in areas with speed restrictions. Unfortunately, these solutions are expensive and difficult to import. Thus, this dissertation's main focus is to produce a detailed blueprint of a radar-based solution, with technical specifications that are similar to those of commercial and experimental systems at relatively low-cost. With the above mindset, the project was initiated with the user requirements being stated. Then a detailed study of current experimental and commercial radar-based traffic calming systems followed. Thereafter, the technical and non-technical requirements were derived from user requirements, and the technical specifications obtained from the literature study. A review of fundamental radar and signal processing principles was initiated to give background knowledge for the design and simulation process. Consequently, a detailed design of the system's functional components was conceptualized, which included the hardware, software, and electrical aspects of the system as well as the enclosure design. With the detailed design in mind, a data-collection system was built. The data-collection system was built to verify whether the technical specifications, which relate to the detection performance and the velocity accuracy of the proposed radar design, were met. This was done to save on buying all the components of the proposed system while proving the design's technical feasibility. The data-collection system consisted of a radar sensor, an Analogue to Digital Converter (ADC), and a laptop computer. The radar sensor was a k-band, Continuous Wave (CW) transceiver, which provided I/Q demodulated data with beat frequencies ranging from DC to 50 kHz. The ADC is an 8-bit Picoscope 2206B portable oscilloscope, capable of sampling frequencies of up to 50 MHz. The target detection and the velocity estimation algorithms were executed on a Samsung Series 7 Chronos laptop. Preliminary experiments enabled the approximation of the noise intensity of the scene in which the radar would be placed. These noise intensity values enabled the relationship between the Signal to Noise Ratio (SNR) and the velocity error to be modelled at specific ranges from the radar, which led to a series of experiments that verified the prototypes' ability to accurately detect and estimate the vehicle speed at distances of up to 40 meters from the radar. The cell-averaging constant false alarm rate (CA-CFAR) detector was chosen as an optimum detector for this application, and parameters that produced the best results were found to be 50 reference cells and 12 guard cells. The detection rate was found to be 100% for all coherent processing intervals (CPIs) tested. The prototype was able to detect vehicle speeds that ranged from 2 km/h up to 60 km/h with an uncertainty of ±0.415 km/h, ±0.276 km/h, and ±0.156 km/h using a CPI of 0.0128 s, 0.256 s, and 0.0512 s respectively. The optimal CPI was found to be 0.0512 s, as it had the lowest mean velocity uncertainty, and it produced the largest first detection SNR of the CPIs tested. These findings were crucial for the feasibility of manufacturing a low-cost traffic calming solution for the South African market

1-D broadside-radiating leaky-wave antenna based on a numerically synthesized impedance surface

A newly-developed deterministic numerical technique for the automated design of metasurface antennas is applied here for the first time to the design of a 1-D printed Leaky-Wave Antenna (LWA) for broadside radiation. The surface impedance synthesis process does not require any a priori knowledge on the impedance pattern, and starts from a mask constraint on the desired far-field and practical bounds on the unit cell impedance values. The designed reactance surface for broadside radiation exhibits a non conventional patterning; this highlights the merit of using an automated design process for a design well known to be challenging for analytical methods. The antenna is physically implemented with an array of metal strips with varying gap widths and simulation results show very good agreement with the predicted performance

Beam scanning by liquid-crystal biasing in a modified SIW structure

A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium

COrE (Cosmic Origins Explorer) A White Paper

COrE (Cosmic Origins Explorer) is a fourth-generation full-sky, microwave-band satellite recently proposed to ESA within Cosmic Vision 2015-2025. COrE will provide maps of the microwave sky in polarization and temperature in 15 frequency bands, ranging from 45 GHz to 795 GHz, with an angular resolution ranging from 23 arcmin (45 GHz) and 1.3 arcmin (795 GHz) and sensitivities roughly 10 to 30 times better than PLANCK (depending on the frequency channel). The COrE mission will lead to breakthrough science in a wide range of areas, ranging from primordial cosmology to galactic and extragalactic science. COrE is designed to detect the primordial gravitational waves generated during the epoch of cosmic inflation at more than $3\sigma$ for $r=(T/S)>=10^{-3}$. It will also measure the CMB gravitational lensing deflection power spectrum to the cosmic variance limit on all linear scales, allowing us to probe absolute neutrino masses better than laboratory experiments and down to plausible values suggested by the neutrino oscillation data. COrE will also search for primordial non-Gaussianity with significant improvements over Planck in its ability to constrain the shape (and amplitude) of non-Gaussianity. In the areas of galactic and extragalactic science, in its highest frequency channels COrE will provide maps of the galactic polarized dust emission allowing us to map the galactic magnetic field in areas of diffuse emission not otherwise accessible to probe the initial conditions for star formation. COrE will also map the galactic synchrotron emission thirty times better than PLANCK. This White Paper reviews the COrE science program, our simulations on foreground subtraction, and the proposed instrumental configuration.Comment: 90 pages Latex 15 figures (revised 28 April 2011, references added, minor errors corrected

Design of Reconfigurable Intelligent Surfaces for Wireless Communication: A Review

Existing literature reviews predominantly focus on the theoretical aspects of reconfigurable intelligent surfaces (RISs), such as algorithms and models, while neglecting a thorough examination of the associated hardware components. To bridge this gap, this research paper presents a comprehensive overview of the hardware structure of RISs. The paper provides a classification of RIS cell designs and prototype systems, offering insights into the diverse configurations and functionalities. Moreover, the study explores potential future directions for RIS development. Notably, a novel RIS prototype design is introduced, which integrates seamlessly with a communication system for performance evaluation through signal gain and image formation experiments. The results demonstrate the significant potential of RISs in enhancing communication quality within signal blind zones and facilitating effective radio wave imaging

Large Space Antenna Systems Technology, part 1

A compilation of the unclassified papers presented at the NASA Conference on Large Space Antenna Systems Technology covers the following areas: systems, structures technology, control technology, electromagnetics, and space flight test and evaluation

System Modeling of Next Generation Digitally Modulated Automotive RADAR (DMR)

abstract: State-of-the-art automotive radars use multi-chip Frequency Modulated Continuous Wave (FMCW) radars to sense the environment around the car. FMCW radars are prone to interference as they operate over a narrow baseband bandwidth and use similar radio frequency (RF) chirps among them. Phase Modulated Continuous Wave radars (PMCW) are robust and insensitive to interference as they transmit signals over a wider bandwidth using spread spectrum technique. As more and more cars are equipped with FMCW radars illuminate the same environment, interference would soon become a serious issue. PMCW radars can be an effective solution to interference in the noisy FMCW radar environment. PMCW radars can be implemented in silicon as System-on-a-chip (SoC), suitable for Multiple-Input-Multiple-Output (MIMO) implementation and is highly programmable. PMCW radars do not require highly linear high frequency chirping oscillators thus reducing the size of the final solution. This thesis aims to present a behavior model for this promising Digitally modulated radar (DMR) transceiver in Simulink/Matlab. The goal of this work is to create a model for the electronic system level framework that simulates the entire system with non-idealities. This model includes a Top Down Design methodology to understand the requirements of the individual modules’ performance and thus derive the specifications for implementing the real chip. Back annotation of the actual electrical modules’ performance to the model closes the design process loop. Using Simulink’s toolboxes, a passband and equivalent baseband model of the system is built for the transceiver with non-idealities of the components built in along with signal processing routines in Matlab. This model provides a platform for system evaluation and simulation for various system scenarios and use-cases of sensing using the environment around a moving car.Dissertation/ThesisMasters Thesis Engineering 201