Finite-difference time-domain simulations have been made of a security screening polarimetric radar over the band 18 GHz to 26 GHz, comparing the results with a proof-of-concept system operating over the same band. The proof-of-concept radar is presented together with its calibration and measurement set-up. Measurements indicate the cross-polarisation returns from a human subject are approximately 10 % to 25 % of the co-polarisation returns. A simulation model has been built using the openEMS software to simulate the body of a human, using realistic primitive shapes and electrical properties appropriate for these frequencies, indicating cross-polar returns are in the region of 15 % of the co-polar responses, with the duration of the reflections lasting around 2 ns. The comparisons between the measurements and simulations are good and provide a qualitative understanding of what happens when security screening radar radiation impinges on the human body. The simulation is extended to two simple enclosures, a cubic box and a short cylinder having dimensions of 300 mm and wall thicknesses of 5 mm, which could be made of wood, cardboard, paper or plastic. Results indicate the cross-polar reflection ranges from 3% to 75 % of the co-polar and bursts of reflections are commensurate with reflections from the front and back surfaces, these being separated in time by 2 ns.
Surrogate explosives and shrapnel weapons at a range of 2 metres have been measured using a full polarimetric radar operating over the band 18-26 GHz. Measurements of these items were made as they were standing by themselves and as they were placed on the body, under light clothing. These measurements were compared with measurements made of the divested human body. The polarimetric radar comprised a vector network analyser, and orthomode transducer and a waveguide conical horn antenna. The measurements were analysed using the Euler/Huynen decompositions and the Cloude/Pottier decompositions working on the coherency matrix, as derived from multiple time sequence measurements. The results conclude that the signature of threat items changes considerably when they are placed on the human body. The measured signature of the threat item on the body appears to be somewhere between that of the threat item when it is by itself and that of the divested human body.
The measurements of the human torso for two individuals are presented via the generation of the Huynen polarisation fork technique and plotted on the Poincaré sphere, to ascertain characteristics that could be used to remove the effects of the torso when concealed weapons are placed against it. Measurements are taken with a frequency modulated continuous wave (FMCW) mono-static millimetre wave full polarimetric radar, operating at k-band (18 to 26 GHz). The system has been designed to explore the feasibility of using full polarimetry for the detection of concealed weapons, and person borne improvised explosive devices (PBIED). The philosophy of this scheme is a means to extract the maximum information content from a target which is in the nominally single spatial pixel (sometimes sub-pixel) configuration of stand-off (tens of metres) and crowd surveillance scenarios. The radar comprises a vector network analyser (VNA) and an orthomode transducer.
The Huynen polarisation fork as a representation of the full polarimetric radar signature represents a unique and natural description of a target. This paper investigates the use of full polarimetric radar operating over the band 18-26 GHz to measure the Huynen target parameters of size, orientation, helicity, skip angle and fork angle from a range of canonical polarimetric radar targets and classic concealed weapon surrogates. Measurement will determine how accurately the Huynen target parameters represent the geometries of the canonical targets and surrogate weapons such as concealed metal and ceramic guns, shrapnel and plane sheet dielectrics. Target backgrounds will be large area absorbers and the human body to enable assessment of the capability for stand-off concealed weapons detection. The system used for the measurement comprises a dual channel vector network analyser, a Turnstile orthomode transducer (OMT) and a conical horn antenna. The OMT has an isolation better than -35 dB between orthogonal polarisations. This system measures and calibrates the Sinclair matrices of targets, from which the Huynen target parameters are derived. A simple model of targets based on the original work in Huynen thesis back in 1970 will be presented, enabling comparison between measured and simulated Huynen target parameters to be made. Conclusions are that experimental measurements of the Huynen target parameters of canonical and surrogate targets agree well with the basic theory of the technique and simple model simulations.
The development and measurements are described of a frequency modulated continuous wave (FMCW) mono-static millimetre wave full polarimetric radar, operating at k-band (18 to 26 GHz). The system has been designed to explore the feasibility of using full polarimetry for the detection of concealed weapons, and person borne improvised explosive devices (PBIED). The philosophy of this scheme is a means to extract the maximum information content from a target which is normally in the single spatial pixel (sometimes sub-pixel) configuration in stand-off (tens of metres) and crowd surveillance scenarios. The radar comprises a vector network analyser (VNA), an orthomode transducer and a conical horn antenna. A calibration strategy is discussed and demonstrated using a variety of known calibration targets with known reflective properties, including a flat metal plate, dihedral reflector, metal sphere, helix and dipole. The orthomode transducer is based on a high performance linear polarizer of the turnstile type with isolation better than - 35dB between orthogonal polarisations. The calibration enables the polarimetric Sinclair scattering matrix to be measured at each frequency for coherent polarimetry, and this can be extended using multiple measurements via the Kennaugh matrix to investigate incoherent full polarimetry.
The QUIJOTE-CMB project has been described in previous publications. Here we present the current status of the
QUIJOTE multi-frequency instrument (MFI) with five separate polarimeters (providing 5 independent sky pixels): two
which operate at 10-14 GHz, two which operate at 16-20 GHz, and a central polarimeter at 30 GHz. The optical
arrangement includes 5 conical corrugated feedhorns staring into a dual reflector crossed-draconian system, which
provides optimal cross-polarization properties (designed to be < −35 dB) and symmetric beams. Each horn feeds a novel
cryogenic on-axis rotating polar modulator which can rotate at a speed of up to 1 Hz. The science driver for this first
instrument is the characterization of the galactic emission. The polarimeters use the polar modulator to derive linear
polar parameters Q, U and I and switch out various systematics. The detection system provides optimum sensitivity
through 2 correlated and 2 total power channels. The system is calibrated using bright polarized celestial sources and
through a secondary calibration source and antenna. The acquisition system, telescope control and housekeeping are all
linked through a real-time gigabit Ethernet network. All communication, power and helium gas are passed through a
central rotary joint. The time stamp is synchronized to a GPS time signal. The acquisition software is based on PLCs
written in Beckhoffs TwinCat and ethercat. The user interface is written in LABVIEW. The status of the QUIJOTE MFI
will be presented including pre-commissioning results and laboratory testing.
The QUIJOTE (Q-U-I JOint Tenerife) CMB Experiment will operate at the Teide Observatory with the aim
of characterizing the polarisation of the CMB and other processes of Galactic and extragalactic emission in the
frequency range of 10-40GHz and at large and medium angular scales. The first of the two QUIJOTE telescopes
and the first multi-frequency (10-30GHz) instrument are already built and have been tested in the laboratory.
QUIJOTE-CMB will be a valuable complement at low frequencies for the Planck mission, and will have the
required sensitivity to detect a primordial gravitational-wave component if the tensor-to-scalar ratio is larger
than r = 0.05.
A. Mennella, B. Aja, E. Artal, M. Balasini, G. Baldan, P. Battaglia, T. Bernardino, M. Bersanelli, E. Blackhurst, L. Boschini, C. Burigana, R. Butler, B. Cappellini, F. Colombo, F. Cuttaia, O. D'Arcangelo, S. Donzelli, R. Davis, L. De La Fuente, F. Ferrari, L. Figini, S. Fogliani, C. Franceschet, E. Franceschi, T. Gaier, S. Galeotta, S. Garavaglia, A. Gregorio, M. Guerrini, R. Hoyland, N. Hughes, P. Jukkala, D. Kettle, M. Laaninen, P. Lapolla, D. Lawson, R. Leonardi, P. Leutenegger, G. Mari, P. Meinhold, M. Miccolis, D. Maino, M. Malaspina, N. Mandolesi, M. Maris, E. Martinez-Gonzalez, G. Morgante, L. Pagan, F. Pasian, P. Platania, M. Pecora, S. Pezzati, L. Popa, T. Poutanen, M. Pospieszalski, N. Roddis, M. Salmon, M. Sandri, R. Silvestri, A. Simonetto, C. Sozzi, L. Stringhetti, L. Terenzi, M. Tomasi, J. Tuovinen, L. Valenziano, J. Varis, F. Villa, A. Wilkinson, F. Winder, A. Zacchei
In this paper we present the test results of the qualification model (QM) of the LFI instrument, which is being
developed as part of the ESA Planck satellite. In particular we discuss the calibration plan which has defined
the main requirements of the radiometric tests and of the experimental setups. Then we describe how these
requirements have been implemented in the custom-developed cryo-facilities and present the main results. We
conclude with a discussion of the lessons learned for the testing of the LFI Flight Model (FM).
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