T. D. Carozzi

University of Glasgow, Glasgow, SCT, United Kingdom

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Publications (70)73.5 Total impact

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  • 12/2013;
  • T.D. Carozzi, G. Woan
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    ABSTRACT: Many modern radio applications, such as astronomy and remote sensing, require high-precision polarimetry. These applications put exacting demands on radio polarimeters (antenna systems that can measure the state of polarization of radio sources), and in order to assess their polarimetric performance, a figure of merit (FoM) would be desirable. Unfortunately, we find that the parameter commonly used for this purpose, the cross-polarization ratio, is not suitable as a polarimetry FoM unless it is given in an appropriate coordinate system. This is because although the cross-polarization ratio is relevant for raw, uncalibrated polarimetry, in general it is not relevant to the quality of the polarimetry after polarimetric calibration. However, a cross-polarization ratio can be constructed from invariants of the Jones matrix (the matrix that describes the polarimetric response of a polarimeter) that quantifies polarimetric performance even after calibration. We call this cross-polarization ratio the intrinsic cross-polarization ratio (IXR) and conclude that it is a fundamental FoM for polarimeters. We then extend the IXR concept from the Jones calculus to the Mueller calculus and also to interferometers, and we give numerical examples of these parameters applied to the Parkes radio telescope, the Westerbork synthesis radio telescope, and the Effelsberg telescope.
    IEEE Transactions on Antennas and Propagation 07/2011; · 2.33 Impact Factor
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    ABSTRACT: Recently, a serial implementation of the one-bit auto- and cross-correlation functions (ACF and CCF respectively) in a field programmable gate array (FPGA) has been developed, based on asynchronous delay elements and counters, known as the counterbased correlation. This paper proposes a method of parallelizing this otherwise serial process, offering significant improvements in the applicability of this approach to more types of ACF. Furthermore, the possibility of obtaining lag results from a parallel data sequence without first shifting the entire sequence has been realized, hence decreasing the number of clock cycles necessary for the calculation of the ACF. A synchronous design was preferred here for reasons of stability and portability, the technology of choice again being an FPGA. The advantages offered by the counterbased implementation in terms of device area usage and speed still apply. A practical implementation in the instrumentation of an upcoming space mission is also discussed.
    Microprocessors and Microsystems - Embedded Hardware Design. 01/2011; 35:297-307.
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    ABSTRACT: Singular value decomposition (SVD) allows the factorization of real or complex matrices providing quantitative information with fewer dimensions along which data points exhibit more variation. These days SVD computation is being used in numerous applications, and because of its importance, different approaches for SVD hardware computation have been proposed, however, their application is limited by the inherent SVD calculation complexity making it possible to analyze up to 8 x 8 matrices until now, complying certain constrains like symmetry. This paper presents a generic and novel FPGA-based hardware architecture for SVD computation on large m × n matrices utilizing Hestenes approach and one-side Jacobi rotations. Four different study cases (2 x 2, 8 x 7, 16 x 32, and 32 x 127 matrices) validate the performance of the FPGA-based computation unit reaching a maximum estimation error of 3.3718 % in the SVD estimation of a large matrix.
    2011 International Conference on Reconfigurable Computing and FPGAs, ReConFig 2011, Cancun, Mexico, November 30 - December 2, 2011; 01/2011
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    ABSTRACT: We used bottomside ground observations and topside sounding data from the Intercosmos-19 satellite to study a Travelling Ionospheric Disturbance (TID) that occurred in response to Large-Scale Internal Gravity Wave (LSIGW) propagation during a substorm on November 30, 1979. We built a global scheme for the wavelike ionospheric variations during this medium substorm (AEmax ∼800 nT). The area where the TID was observed looks like a wedge since it covers the nighttime hours at subauroral latitudes but contracts to a ∼02 h local sector at low latitudes. The ionospheric response is strongly asymmetric because the wedge area and the TID amplitude are larger in the winter hemisphere than in the summer hemisphere. Clear evidence was obtained indicating that the more powerful TID from the Northern (winter) hemisphere propagated across the equator into the low latitude Southern (summer) hemisphere. Intercosmos-19 observations show that the disturbance covers the entire thickness of the topside ionosphere, from hmF2 up to at least the 1000 km satellite altitude at post-midnight local times. F-layer lifting reached ∼200 km, Ne increases in the topside ionosphere by up to a factor of ∼1.9 and variations in NmF2 of both signs were observed. Assumptions are made concerning the reason for the IGW effect at high altitudes in the topside ionosphere. The relationship between TID parameters and source characteristics determined from a global network of magnetometers are studied. The role of the dayside cusp in the generation of the TID in the daytime ionosphere is discussed. The magnetospheric electric field effects are distinguished from IGW effects.Research Highlights► The global scheme for the large-scale TID propagation during a substorm is built. ► TID covers the entire thickness of the topside ionosphere. ► The area where the TID is observed looks like a wedge directed to the equator. ► TID area and amplitude are larger in the winter hemisphere than in the summer hemisphere. ► The more powerful TID from the winter hemisphere propagates into the summer hemisphere.
    Journal of Atmospheric and Solar-Terrestrial Physics 01/2011; 73:567-577. · 1.42 Impact Factor
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    ABSTRACT: Recent discoveries concerning rotating (helical) phase fronts and orbital angular momentum (OAM) of laser beams are applied to radio frequencies and comprehensive simulations of a radio OAM system are performed. We find that with the use of vector field-sensing electric and magnetic triaxial antennas, it is possible to unambiguously estimate the OAM in radio beams by local measurements at a single point, assuming ideal (noiseless) conditions and that the beam axis is known. Furthermore, we show that conventional antenna pattern optimization methods can be applied to OAM-generating circular arrays to enhance their directivity.
    IEEE Transactions on Antennas and Propagation 03/2010; · 2.33 Impact Factor
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    ABSTRACT: Novel measurement and approximation methodologies for studying orbital angular momentum (OAM) modes in radio beams, i.e., electromagnetic beam modes having helical phase fronts, are presented. We show that OAM modes can be unambiguously determined by measuring two electric field components at one point, or one electric field component at two points.
    Radio Science 01/2010; 45(4). · 1.00 Impact Factor
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    ABSTRACT: Variations in the dayside ionosphere parameters as a result of a large-scale acoustic gravity wave (LS AGW) were studied for the 17 February 1998 substorm using the super dual auroral radar network (SuperDARN) measurements. This event was characterised by a sharp rise in the AE index with a maximum of ∼900 nT. The source of the disturbance responsible for the LS AGW appears to have been located within the plasma convection throat and in the dayside cusp region. The location of the source was obtained from studies of a number of datasets including high-latitude convection maps, data from 4 DMSP satellites and networks of ground-based magnetometers. The propagation of the LS AGWs caused quasi-periodic variations in the skip distance (with an amplitude up to 220–260 km) of the ground backscatter measured by up to 6 SuperDARN radars, including Goose Bay and Kapuskasing, resulting in two large-scale travelling ionospheric disturbances (LS TIDs). The LS TIDs had wave periods of 1.5 and 2 h, a velocity of ∼400 m/s for both, and wavelengths of 2200 and 2900 km, respectively. These quasi-periodic variations were also present in the peak electron density and height of the F2 layer measured by the Goose Bay ionosonde. The numerical simulation of the inverse problem show good agreement between Goose Bay radar and Goose Bay ionosonde measurements. But these LS TIDs would be difficult to deduce from the ground based ionospheric station data alone, because hmF2 variations were 10–40 km only and fOF2 variations between 10% and 20%. The results demonstrate how important SuperDARN radars can be, and that this is a more powerful technique than routine ground-based sounding for studies of weak quasi-periodic variations in the dayside subauroral ionosphere related to LS AGW.
    Journal of Atmospheric and Solar-Terrestrial Physics 01/2010; · 1.42 Impact Factor
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    ABSTRACT: The Digital Wave Processor (DWP) is the central control and data processing instrument for the Cluster Wave Experiment Consortium. DWP products in the Cluster Active Archive (CAA) provide a mainly supporting function for the rest of the consortium. This includes a time correction dataset which allows the standard timing accuracy of 2 ms to be improved to around 20 μs, and experiment command and status datasets which show what commands have been sent to the experiments, and the resulting status. DWP also contains a particle correlator experiment that computes the auto-correlation of electron counts received by the PEACE electron experiment via an inter-experiment link.
    12/2009: pages 73-82;
  • T D Carozzi, G Woan, R Maaskant
    Widefield Science and Technology for the mboxSKA -- mboxSKADS Conference 2009; 11/2009
  • T. D. Carozzi, G. Woan
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    ABSTRACT: This paper has been withdrawn to allow publication elsewhere. Comment: This paper has been withdrawn
    IEEE Transactions on Antennas and Propagation 08/2009; · 2.33 Impact Factor
  • T. D. Carozzi, G. Woan, R. Maaskant
    01/2009;
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    T. D. Carozzi, G. Woan
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    ABSTRACT: We derive a generalised van Cittert-Zernike (vC-Z) theorem for radio astronomy that is valid for partially polarized sources over an arbitrarily wide field-of-view (FoV). The classical vC-Z theorem is the theoretical foundation of radio astronomical interferometry, and its application is the basis of interferometric imaging. Existing generalised vC-Z theorems in radio astronomy assume, however, either paraxiality (narrow FoV) or scalar (unpolarized) sources. Our theorem uses neither of these assumptions, which are seldom fulfilled in practice in radio astronomy, and treats the full electromagnetic field. To handle wide, partially polarized fields, we extend the two-dimensional electric field (Jones vector) formalism of the standard "Measurement Equation" of radio astronomical interferometry to the full three-dimensional formalism developed in optical coherence theory. The resulting vC-Z theorem enables all-sky imaging in a single telescope pointing, and imaging using not only standard dual-polarized interferometers (that measure 2-D electric fields), but also electric tripoles and electromagnetic vector-sensor interferometers. We show that the standard 2-D Measurement Equation is easily obtained from our formalism in the case of dual-polarized antenna element interferometers. We find, however, that such dual-polarized interferometers can have polarimetric aberrations at the edges of the FoV that are often correctable. Our theorem is particularly relevant to proposed and recently developed wide FoV interferometers such as LOFAR and SKA, for which direction-dependent effects will be important. Comment: To be published in MNRAS
    Monthly Notices of the Royal Astronomical Society 11/2008; · 5.52 Impact Factor
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    ABSTRACT: Electromagnetic waves with an azimuthal phase shift are known to have a well defined orbital angular momentum. Different methods that allow for the detection of the angular momentum are proposed. For some, we discuss the required experimental setup and explore the range of applicability.
    06/2008;
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    Jan E. S. Bergman, Tobia D. Carozzi
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    ABSTRACT: We present a new characterization of partially coherent electric and magnetic wave vector fields.This characterization is based on the 36 auto/cross correlations of the 3+3 complex Cartesian components of the electric and magnetic wave fields and is particularly suited for analyzing electromagnetic wave data on board spacecraft. Data from spacecraft based electromagnetic wave instruments are usually processed as data arrays. These data arrays however do not have a physical interpretation in themselves; they are simply a convenient storage format. In contrast, the characterization proposed here contains exactly the same information but are in the form of manifestly covariant space-time tensors. We call this data format the Canonical Electromagnetic Observables (CEO) since they correspond to unique physical observables. Some of them are already known, such as energy density, Poynting flux, stress tensor, etc, while others should be relevant in future space research. As an example we use this formalism to analyze data from a chorus emission in the mid-latitude magnetosphere, as recorded by the STAFF-SA instrument on board the Cluster-II spacecraft.
    05/2008;
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    ABSTRACT: Starting from positive and negative helicity Maxwell equations expressed in Riemann-Silberstein vectors, we derive the ten usual and ten additional Poincar{\'e} invariants, the latter being related to the electromagnetic spin, i.e., the intrinsic rotation, or state of polarization, of the electromagnetic fields. Some of these invariants have apparently not been discussed in the literature before.
    04/2008;
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    ABSTRACT: This paper presents a novel algorithm, called the DFSWT, and its FPGA-based hardware processing unit for frequency estimation of a time series main periodic component. Since the DFSWT uses just additions and subtractions, it is simpler to compute than the FFT, and since its spectrum is a frequency function, it is more intuitive than the Walsh transform. The results show that the proposed algorithm is very efficient in detecting the frequency of the main periodic component, even in low SNR. The proposed hardware processing unit is 3 orders of magnitude faster than its respective software implementation and presents advantages regarding to power consumption, footprint, and computation speed against highly optimized commercially available FFT cores.
    Digital Signal Processing. 01/2008;
  • WISER Alfvén 2007 Workshop on Space Environment Turbulence, Warsaw, Poland; 09/2007
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    ABSTRACT: We show numerically that vector antenna arrays can generate radio beams that exhibit spin and orbital angular momentum characteristics similar to those of helical Laguerre-Gauss laser beams in paraxial optics. For low frequencies (< or = 1 GHz), digital techniques can be used to coherently measure the instantaneous, local field vectors and to manipulate them in software. This enables new types of experiments that go beyond what is possible in optics. It allows information-rich radio astronomy and paves the way for novel wireless communication concepts.
    Physical Review Letters 08/2007; 99(8):087701. · 7.73 Impact Factor

Publication Stats

585 Citations
73.50 Total Impact Points

Institutions

  • 2007–2011
    • University of Glasgow
      • School of Physics and Astronomy
      Glasgow, SCT, United Kingdom
  • 2003–2011
    • University of Sussex
      • Biomedical Engineering Group
      Brighton, England, United Kingdom
  • 2007–2010
    • University of Leicester
      • Department of Physics and Astronomy
      Leicester, ENG, United Kingdom
  • 1997–2010
    • Swedish Institute of Space Physics
      Kiruna, Norrbotten, Sweden