J. C. Iriarte

Thin AMC Structure for Radar Cross-Section Reduction

A thin artificial magnetic conductor (AMC) structure is designed and breadboarded for radar cross-section (RCS) Reduction applications. The design presented in this paper shows the advantage of geometrical simplicity while simultaneously reducing the overall thickness (for the current design ). The design is very pragmatic and is based on a combination of AMC and perfect electric conductor (PEC) cells in a chessboard like configuration. An array of Sievenpipers mushrooms constitutes the AMC part, while the PEC part is formed by full metallic patches. Around the operational frequency of the AMC-elements, the reflection of the AMC and PEC have opposite phase, so for any normal incident plane wave the reflections cancel out, thus reducing the RCS. The same applies to specular reflections for off-normal incidence angles. A simple basic model has been implemented in order to verify the behavior of this structure, while Ansoft-HFSS software has been used to provide a more thorough analysis. Both bistatic and monostatic measurements have been performed to validate the approach.

EBG Superstrate Array Configuration for the WAAS Space Segment

Two different electromagnetic bandgap (EBG) superstrate array antenna configurations, intended for the wide area augmentation service space segment, are presented in this paper. The described antenna configurations take advantage of the directivity enhancement produced by a semireflective sheet placed parallel to a metallic ground plane. The first design presented is realized using a 2times2 circularly polarized (CP) patch array illuminating an EBG superstrate composed of a square pattern of circular holes etched in a thin metallic sheet. The second design consists of a 2times2 CP helix array feeding a hexagonal pattern of holes etched into a metallic EBG superstrate. Both configurations have been designed, breadboarded, and measured, and excellent agreement between simulations and measurements has been recorded. The accurate control of the antenna pattern phase center variation with both the frequency and the antenna field of view, necessary for the intended navigation antenna application, has been the principal challenge of this work. The EBG technology designs presented here are simpler than conventional navigation antennas and can lead to cost reduction, beamforming network simplification, and height reduction while offering similar radio-frequency performances to equivalent products realized in conventional technology.

THz imaging system for industrial quality control

THz imaging technology can complement quality controls in Agricultural and food industry due to the new point of view offered by THz. In this paper, an active THz imaging system based on a network analyzer with two frequency extender up to 0.22THz and a quasioptical system is presented. The resolution of the system is measured using metal squares placed on a leaf. This metal squares are used to show differences in power absorption levels. Defects are also placed in one sample, in order to check the possibilities offered by THz imaging to detect unwanted objects and defects in a leaf.

Combination of AMC and PEC cells for RCS applications

A combination of perfect electric conductor (PEC) and artificial magnetic conductor (AMC) cells with a periodicity around lambda can be applied to improve the RCS, by reducing the power scattered in the specular direction. A 180deg phase difference is created between the contribution from the PEC and AMC cells, obtaining destructive interference. A theoretical model is presented based on array theory which agrees with the simulated results using the commercial software Ansoft HFSS. The structure has been breadboarded and tested. Results match the predictions and will be presented at the conference.

EBG antenna technology for different applications

EBG technology has been shown in last years as an alternative for designer which can benefit from the different properties presented by these periodic structures. However, the number of designs which comply with specifications of tangible applications were limited. Therefore the work presented in this paper is focused in showing the advantages that can be achieved by the used of EBG technology, covering specific applications, taking advantage of diverse properties of EBG materials, i.e.: the presence of a forbidden frequency band (bandgap); the design of resonant cavities which can be used to elongate the radiation aperture of antennas, increasing consequently the directivity; or at last, the use of the property presented by EBG - AMC (Artificial Magnetic Conductor) structures to reflect incident waves with a 0° phase value at the working frequency, behaving as a perfect magnetic conductor.

High dielectric constant EBG technology to avoid gratings lobes and scan blindness in array configurations

High dielectric electromagnetic band gap (EBG) substrates can be used in patch antenna configurations to reduce size and mitigate substrate modes propagation with reasonable radiation efficiency values (ηrad > 0.55). Furthermore, EBG substrate structures applied in array configurations are able to avoid grating lobes and scan blindness phenomena as distance and coupling between patch antenna-radiating elements can be reduced at the same time. In this paper, a 2 × 2 array configuration using Zirconium Tin Titanate EBG substrate with high dielectric constant is presented. The array has been simulated showing 9 dB coupling reduction obtained by the inclusion of the EBG substrate in between the patch antennas placed to a distance lower than 0,5λ0. This short distance together with the coupling reduction results in a configuration which does not suffer from grating lobes and scan blindness problems, obtaining a 30º scan angle for the 2 × 2 configuration which is the maximum achievable angle due to a 2 × 2 array factor. A scan angle larger than 70º can be seen for the infinite configuration.

Explosives characterization in terahertz range

A Thz spectral characterization of the behaviour of different explosives is presented in this paper. This characterization will be done in the frequency range from 20 GHz to 4 THz using a Teraview Spectra 3000. This system has a capacity of measuring from 20 GHz to 4 THz fed by a laser source. With the Teraview Spectra 3000 equipment will be possible to calculate the refractive index, the absorbance and other important parameters of the explosive samples. With this study it will be possible to characterize some of the most common used explosives, i.e., gun explosive, gunpowder mine, pent, TNT, RDX, etc, and it will allow to determine their electromagnetic peculiarities in order to design a future imaging system that allow detecting them in security and defense sectors.