E. Saenz

Universidad Pública de Navarra, Iruña, Navarre, Spain

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Publications (42)31.11 Total impact

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    ABSTRACT: In this paper, an LHCPSS based on the Pierrot cell has been theoretically studied and demonstrated experimentally. Design guidelines are given and an accurate fabrication process has been developed. Measurements of a fabricated prototype exhibit performance compliant with the requirements for space applications over a limited bandwidth. Axial ratio and insertion loss smaller than 1 and 0.5 dB, respectively, over a 7% bandwidth have been achieved at 9.8 GHz. Wider bandwidths with low axial ratio are possible by relaxing the requirements in terms of insertion loss.
    No preview · Article · Jun 2015 · IEEE Transactions on Antennas and Propagation
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    ABSTRACT: A new class of polarizing surface is proposed that in a given frequency band can reflect incident linearly polarized waves with circular polarization (CP) while at other frequencies is transparent allowing incident waves to transmit unaffected. The proposed structure consists of two parallel anisotropic frequency selective surfaces (FSSs) that independently interact with TE or TM waves, respectively. The FSSs are designed to, respectively, transmit TE and TM waves within the same transmission frequency range, so that the combined structure is transparent to all polarizations in this band. Likewise, the two arrays are designed to, respectively, reflect TE and TM incident waves in a common reflection band, so that all polarizations are fully reflected in this range; if the separation of the two arrays is such that the TE and TM components of an incident wave polarized at slant 45° experience a 90° phase shift, reflection will occur in CP. The concept and performance limitations are theoretically investigated using transmission line theory as well as full wave results. The predicted performance is validated by means of experimental results on a fabricated prototype. The proposed structure is pertinent for employment as a quasi-optical diplexer in CP dual-band systems such as reflector antennas.
    Full-text · Article · May 2015 · IEEE Transactions on Antennas and Propagation
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    ABSTRACT: Single and double layer frequency selective surfaces (FSS) for Circular polarization (CP) operation were designed. The designed FSS provide reflection in the Ku-band (11.7-12.75 GHz) and transmission in the Ka-band (17.3-20.2 GHz). CP is conserved in each of the bands. For the double layer design over the Ku-band the reflection loss was less than 0.05 dB for TE and TM polarizations while the axial ratio was below 0.2 dB. Over the Ka-band transmission loss and axial ratio were each less than 0.25 dB.
    Full-text · Conference Paper · Apr 2014
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    ABSTRACT: This paper demonstrates a method for material characterization (permittivity, permeability, loss tangent) based on the scattering parameters. The performance of the extraction algorithm will be shown for modelled and measured data. The measurements were carried out at the European Space Agency using two free space test facilities for material characterization. In order to improve the accuracy of the measurements and to remove possible systematic errors in the setup, different calibration techniques are investigated.
    No preview · Conference Paper · Apr 2014
  • E. Saenz · L. Rolo · M. Kaniecki
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    ABSTRACT: In this paper, the accuracy of the Quasi-Optical free-space test bench for reflectivity measurements at W-band and 110-170 GHz is evaluated. A sample from the MADRAS (Microwave Analysis and Detection of Rain and Atmospheric Structures) Spaceborne Radiometer already measured at the Institute of Applied Physics of the Russian Academy of Sciences (IAP RAS) (Nizhniy Novgorod, Russia) was used as reference. Two calibration procedures are considered in order to improve the accuracy of the measurements.
    No preview · Conference Paper · Apr 2014
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    ABSTRACT: The performance of circular polarization selective surfaces (CPSS) under oblique incidence is examined experimentally. A fabricated CPSS prototype working around 10GHz has been characterized under oblique incidence ranging angles between ±30°. It was found that increasing the angle of incidence, the frequency at which minimal axial ratio (AR) is achieved deviates from the resonant frequency of the CPSS, resulting in higher AR within a given bandwidth. Design guidelines will be given in order to minimize this limitation.
    No preview · Conference Paper · Apr 2014
  • R. Appleby · E. Saenz · R. Wylde · S. Froud
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    ABSTRACT: An instrument has been designed which is capable of measuring scattering from 0.075-0.5 THz. This will enable a more accurate determination of the optical properties of materials by correcting for scatter and also the characterisation of the mechanical properties of the surface. Models have been investigated to help in experimental design and in reducing the number of required measurements by extrapolation. The Generalized Harvey Shack (GHS) method has been evaluated for this purpose. Predictions for 40 grit gold coated sandpaper at 37 degrees incidence angle and 0.8 THz are made showing the surface to be almost completely diffuse. The GHS method was compared to the Integral Equation Model (IEM).
    No preview · Conference Paper · Apr 2014
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    ABSTRACT: A detailed broadband analysis of energetic materials using THz time-domain spectroscopy with a bandwidth from 0.2 to 6.4 THz is presented. Dependencies of the resonance features on different sample parameters are evaluated via spectroscopic investigation of several energetic materials (TNT, C4, RDX, PETN, AN) in transmission and reflection experiments. A strong dependency of the resonance features on the manufacturing process of an explosive is observed especially with TNT. The THz measurements of the TNT samples are compared to powder X-ray diffraction measurements. Furthermore, it is observed that additive compounds with a flat frequency response offset the THz reflection of an explosive, but the recognition capability of a resonance feature is not influenced.
    No preview · Article · Sep 2013 · IEEE Transactions on Terahertz Science and Technology
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    ABSTRACT: The realization of a Circular Polarization Selective Surface (CPSS) exhibiting low Axial Ratio (AR) has been demonstrated experimentally in the X band, showing good agreement with the simulated response. The fabricated CPSS has been characterized using a free-space collimator system recently acquired by ESA. An AR below 1dB, which is comparatively smaller than previous results shown in the literature, has been achieved for more than 20% bandwidth.
    No preview · Conference Paper · Jul 2013
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    ABSTRACT: A detailed broadband analysis of the resonant absorptions of different common explosives in the range from 0.1-6 THz is presented. Dependencies of the resonance features on different sample parameters are evaluated via spectroscopic investigation of transmission and reflection. A significant dependency on the manufacturing process is observed.
    No preview · Conference Paper · Sep 2012
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    ABSTRACT: The design of dual-optics circular-polarization offset reflectors has been addressed by using circular polarization selective surfaces (CPSS). A novel design of CPSS based on Pierrot's cells is proposed, and design guidelines and limitations of this technology are given. Manufacture constraints are discussed and a more reliable fabrication process is developed. A 29×29 array has been constructed and measurements are ongoing.
    No preview · Conference Paper · Mar 2012
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    ABSTRACT: In this paper accurate material measurements at sub-millimetre wave frequencies performed with two different systems are compared. Transmission and reflection results of high quality samples measured with a quasi-optical open resonator and a quasi-optical free-space bench are presented. Based on the comparison between the two results, an accuracy assessment of the transmission set-up is performed.
    Full-text · Conference Paper · Jan 2012
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    ABSTRACT: The field of antenna measurements is lacking a Golden Standard, i.e. an antenna of which the pattern is known by definition. To gain confidence in the performance of a range, including the procedures and skills of the operators, range comparison has been a popular tool for over three decades. In the beginning, ad-hoc available antennas were shipped around the various ranges. Soon it became clear that the comparisons were restricted by the properties of the antenna. The European Space Agency (ESA) stimulated and supported the development of a dedicated VAlidation STandard (VAST) antenna, specifically designed for validation campaigns of antenna measurement ranges. The driving requirements of VAST antennas are their mechanical stability over a given operational temperature range and with respect to any orientation of the gravity field. The mechanical design shall ensure extremely stable electrical characteristics allowing frequent travel and shall ease the handling of the VAST antenna (practical electrical and mechanical interfaces, well-defined alignment tools, low mass, attachment points for lifting, etc). The widespread use of the so-called VAST-12 antenna demonstrates the long-term value of dedicated test antennas. Currently, ESA is considering expanding its set of validation elements developing a VAST antenna at mm-waves. The frequencies considered are application driven: 20/30 GHz as up/down link of Ka-Sat, 38/48 GHz as up/downlink of Alphasat, thus, covering the Ku/Ka-band and the upcoming Q/V-band of telecom satellites. The paper will address requirements for future VASTs and possible architecture for multi-frequency Validation Standard antennas.
    No preview · Conference Paper · May 2011
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    ABSTRACT: In this paper the material characterization at sub- millimetre wave frequencies facility recently developed at the European Space Research and Technology Centre (ESA-ESTEC) to complement existing antenna ranges is presented. By means of a Quasi Optical test bench, transmission/reflection measurements from 50 to 500 GHz are performed. Complex material parameters are then calculated from transmission measurements. As a first experimental campaign and in support to industry the transmission properties of several energetic materials (C4, RDX, TNT, PETN and Semtex-H) and barrier materials have been measured and material parameters extracted.
    No preview · Article · Jan 2011
  • I. Liberal · I. Ederra · E. Saenz · R. Gonzalo
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    ABSTRACT: This contribution analyzes several multi-frequency antenna systems based on meta-surfaces. As it is demonstrated, there is a synergy between the frequency-domain behavior of the meta-surface and multi-frequency antenna architectures. Therefore, the use of the meta-surface is not restricted to enhance the radiation properties of the single-antenna element, but also contributes at system level aspects such us isolation and compactness.
    No preview · Conference Paper · Jan 2011
  • K. Guven · E. Saenz · R. Gonzalo · E. Ozbay · S. Tretyakov
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    ABSTRACT: We investigate the application of a metamaterial that is formed by the sparse distribution of spiral resonators as an optical transformation medium is in order to achieve electromagnetic cloaking. The well-known Clausius-Mossotti formula relates the microscopic polarizability of a single resonant particle to the macroscopic permittivity and permeability of the effective medium. By virtue of transformation optics, the permittivity and permeability of the medium, in turn, can be designed according to a coordinate transformation that maps a certain region of space to its surrounding. As a result, the mapped region can be cloaked from electromagnetic waves. In this study, the spirals are optimized to exhibit equal permittivity and permeability response so that the cloak formed by these spirals will work for both the TE and TM polarizations. An experimental setup is developed to visualize the steady state propagation of electromagnetic waves within a parallel plate waveguide including the cloaking structure. The measured and simulated electromagnetic field image indicates that the forward scattering of a metal cylinder is significantly reduced when placed within the cloak.
    No preview · Article · Apr 2010 · Proceedings of SPIE - The International Society for Optical Engineering
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    Saenz E · Guven K · Ozbay E · Ederra I · Gonzalo R
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    ABSTRACT: The mutual coupling between elements of a multifrequency dipole antenna array is experimentally investigated by S -parameter measurements and planar near-field scanning of the radiated field. A multifrequency array with six dipoles is analyzed. In order to reduce the coupling between dipoles, a planar metasurface is placed atop the array acting as superstrate. The mutual coupling of the antenna elements in the absence and presence of the superstrate is presented comparatively. Between 3 and 20 dB mutual coupling reduction is achieved when the superstrate is used. By scanning the field radiated by the antennas and far-field measurements of the radiation pattern, it is observed that the superstrate confines the radiated power, increases the boresight radiation, and reduces the endfire radiation.
    Full-text · Article · Jan 2010 · International Journal of Antennas and Propagation
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    ABSTRACT: A comparison is made between the two standard methods to characterise the quiet zone in a CATR and the applicability to mm-wave frequencies. The aspects considered are positioner accuracy requirements, dynamic range and measurement times. Typical numbers are given for the ESTEC ranges as representative examples.
    No preview · Conference Paper · Apr 2009
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    ABSTRACT: The mutual coupling between dipole antenna array elements using a planar meta-surface as superstrate is experimentally investigated. The meta-surface is based on grids of short metal strips and continuous wires. A comparison between the mutual coupling when the dipoles are radiating in free space and in presence of the superstrate is presented. On average, between 3 to 14 dB reduction of the mutual coupling is achieved when the superstrate is used. The effect of the mutual coupling on the radiation performance of the array is studied by spherical near-field measurements of the radiation pattern when one driven dipole is fed and the others are matched with 50 Omega loads. The back-projected field on the aperture and on the E-plane is shown.
    Full-text · Article · Mar 2009 · IEEE Transactions on Antennas and Propagation
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    K Guven · E Saenz · R Gonzalo · E Ozbay · S Tretyakov
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    ABSTRACT: We report an electromagnetic cloaking structure that is composed of identical canonical spiral particles. By using the Clausius–Mosotti formula, the electric and magnetic polarizabilities of a single spiral particle are related to the relative permittivity and permeability of the sparse distribution of particles. The permittivity and permeability of the distribution are, in turn, defined according to the coordinate transformation, which leads to the cloaking effect. Spirals are optimized to exhibit equal permittivity and permeability response so that the cloak consisting of these spirals will work for both transverse electric (TE) and transverse magnetic (TM) polarizations. Measurement of the cloaking device surrounding a metal cylinder inside a parallel waveguide was performed. The steady-state propagation of an electromagnetic wave was reconstructed from the amplitude and phase data, which demonstrates that the field largely restores to a free-space propagation pattern after the cloak.
    Full-text · Article · Nov 2008 · New Journal of Physics