A dual-operating-band planar horn antenna having very low profile is presented in this paper. By opening a subwavelength aperture into a corrugated conducting plate, good return losses and a narrow radiated beam in each of the two desired operating frequency bands can be measured. This behavior is very similar to that observed in optical wavelengths where enhanced transmission was measured through apertures etched in metallic corrugated plates. Here, the double-corrugated structure has been scaled into the microwave frequency range and the excitation has been done by a conventional closed metallic waveguide placed in the rear part of the structure. In this way, a new concept of a very low profile feeder is proposed with potential wireless applications.Index Terms-Double-periodic corrugated plate, dual-band, subwavelength aperture, very low profile feeder.
A novel passive repeater, based on a chain of 3D dielectric particles, has been proposed and numerically simulated. The performance of modern computing depends directly on the speed of data exchange between cores. Electrical metal interchip connections, however, are fundamentally limited by their bandwidth, 1 which ultimately determines the maximum data rate. The transition from electronics to photonics-or to nanophotonics, to be precise-may be a possible solution to this problem. 2 This is because optical computing allows speed and productivity to be increased in proportion to the number of cores. 3 The fundamental laws of diffraction, however, mean that the size of photonic components cannot be reduced greatly, i.e., their size cannot be smaller than the order of the operation wavelength. This fundamental problem can be solved by using surface waves instead of volume waves. These surface waves-known as surface plasmon polaritons (SPPs) 4-are based on the interaction of electromagnetic radiation and conduction electrons on metal surfaces. With the SPP strategy, the diffraction limit of classical optics can be overcome, thanks to the smaller wavelength of the SPPs. The possibility of working in the optical near field, with a sub-wavelength size, also opens up and allows nanoscale devices (about 10nm in size) that operate at high speed (about 10THz) to be created. This approach has given rise to an intense amount of research on SPP propagation in the discipline of plasmonics. An important remaining hurdle in the technological development of plasmonics, however, is the relatively short propagation distances of SPPs (caused by their fundamental absorption in metals). 4 In recent work, photonic nanojets (PNJs) 5 were proposed at optical wavelengths combined with SPPs, 6, 7 but the propagation distance of the SPPs was small.
Solar Orbiter is a mission dedicated to solar and heliospheric physics. It was selected as the first mediumclass mission of ESA's Cosmic Vision 2015-2025 Programme. Solar Orbiter will be used to examine how the Sun creates and controls the heliosphere, the vast bubble of charged particles blown by the solar wind into the interstellar medium. One of the scientific payload elements of Solar Orbiter is the Polarimetric and Helioseismic Imager (PHI). The PHI instrument consists of two telescopes, a High Resolution Telescope (HRT) that will image a fraction of the solar disk at a resolution reaching ~150 km at perihelion, and a Full Disk Telescope (FDT) to image the full solar disk during all phases of the orbit. PHI is a diffraction limited, wavelength tunable, quasi-monochromatic, polarisation sensitive imager. These capabilities are needed to infer the magnetic field and line-of-sight (LOS) velocity of the region targeted by the spacecraft. For the spectral analysis, PHI will use an order-sorting filter to isolate a bandpass of the order of 100 mÅ. The FilterGraph (FG) contains an etalon in single pass configuration as tunable spectral filter located inside a temperature stabilized oven. This filter will be made by means of a z-cut LiNbO3 crystal (about 300 microns thick) and multilayer coatings including a conductive one in order to apply a high voltage (up to 5 kV) and induce the required electric field to tune the filter.Solar Orbiter observing mission around the Sun will expose the PHI instrument to extreme radiation conditions, mainly dominated by solar high-energy particles released during severe solar events (protons with energies typically ranging from few keV up to several GeV) and the continuous isotropic background flux of galactic cosmic rays (heavy ions, from Z=1 to Z=92). The main concerns are whether the cumulated radiation damage can degrade the functionality of the filter or, in the worst case, the impact of a single highly ionizing particle, coupled with the HV field, could trigger a dielectric breakdown in the Lithium Niobate.In this paper we present the electro-optical results obtained when exposing a set of LN samples and a lowquality full size etalon to different radiation conditions. In a first irradiation campaign, performed at the Centre for Micro Analysis of Materials (CMAM-Madrid) facilities, we were mainly focused on the long-term degradation effects with a series of high flux (10 9 cm -2 s -1 ) proton tests at an energy of 10 MeV. In order to study the possibility of a single ion breakdown, a second campaign was carried out, at the Texas A&M University (TAMU), exposing Lithium Niobate to high LET ion species ( 78 Kr, 40 Ar, 129 Xe, 197 Au) accelerated to the GeV energy range to penetrate or even pass through the entire Lithium Niobate thickness.
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