Open Access
Planar DNG superstrate for dipole antenna gain enhancement
(2007) Sáenz Sáinz, Elena; Gonzalo García, Ramón; Ederra Urzainqui, Íñigo; Ikonen, Pekka; Tretyakov, Sergei A.; Maagt, Peter de; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
In this paper, a volumetric double-negative (DNG) superstrate based on grids of dipoles and wires for dipole antenna applications is proposed.
Embargo
Experimental validation of a Ku-band dual circularly polarized metasurface antenna
(IEEE, 2018) Tellechea Pereda, Amagoia; Caminita, Francesco; Martini, Enrica; Ederra Urzainqui, Íñigo; Teniente Vallinas, Jorge; Iriarte Galarregui, Juan Carlos; Gonzalo García, Ramón; Maci, Stefano; Ingeniaritza Elektrikoa eta Elektronikoa; Institute of Smart Cities - ISC; Ingeniería Eléctrica y Electrónica
The experimental validation of a Ku-band dual circularly polarized (CP) broadside-beam metasurface (MTS) antenna is presented. A radially modulated anisotropic single layer MTS has been synthesised employing sub-wavelength elliptical slotted metallic patches printed on top of a thin Arlon grounded substrate. In the structure, two decoupled phasematched transverse magnetic and transverse electric surface waves (SWs) are excited, which interact with the modulated surface leading to a CP broadside radiation. Two different orthomode transducers have been designed to excite the SWs with orthogonal polarization and equal amplitude. The first feeding system is composed of a metallic stepped septum inside an airfilled square waveguide. A conical section is included to match the output port of the square waveguide with the terminal, dielectric filled circular waveguide. The second feed is much more compact and efficient and it is composed of a circular waveguide completely filled by a dielectric. Depending on the input port excited on the feeds, two TE11 modes are excited with ±90° phase shift, which determine the right-hand or left-hand sense of the broadside beam generated by the MTS. Manufacturing details of the MTS and excitations are given and the measurements are compared with the simulation results. Finally, conclusions are drawn.
Open Access
Induction theorem analysis of resonant nanoparticles: design of a huygens source nanoparticle laser
(American Physical Society, 2014) Liberal Olleta, Íñigo; Ederra Urzainqui, Íñigo; Gonzalo García, Ramón; Ziolkowski, Richard W.; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
We propose an advanced formulation of standard antenna theory for the basic investigation and design of resonant nanoparticles. This methodology is based on transforming the original scattering problem into a radiation configuration by invoking the induction theorem. Then applying basic antenna theory principles, such as the suppression of any reactive power, the properties of the resonances are engineered. This nanoantenna approach has been validated by revisiting a number of well-known multilayered core-shell structures. It provides additional important physical insights into how the core-shell structures operate and it enables combinations of different resonant phenomena associated with them, e.g., plasmonic and high-ϵ resonances, in an intuitive manner. Its efficacy is demonstrated by designing a multilayered nanoparticle that achieves lasing with a maximum directivity in the forward direction and a null in the backward direction, i.e., a Huygens source nanoparticle laser.
Open Access
Design of a planar meta-surface based on dipoles and wires for antenna applications
(2006) Sáenz Sáinz, Elena; Gonzalo García, Ramón; Ederra Urzainqui, Íñigo; Maagt, Peter de; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
In this paper, the design of a planar meta-surface based on dipoles and wires is presented. The unit cell is formed by three independent layers, which contain two parallel dipoles and one wire. The behaviour of these elements have been analysed separately as an independent unit cell, i.e., the one dipole unit cell, the two dipoles unit cell and the two dipoles and wire unit cell, by means of the transmission response and the dispersion diagrams. For a normal incident plane wave with the E field parallel to the wires and the H field axial to the dipoles, the electric and magnetic responses are excited producing a pass band behaviour which exhibit negative refractive index. This cell has been used to create meta-surfaces for antenna applications. Two configurations have been analysed; the first one is a superstrate of a dipole antenna with the pass band tuned to the resonant frequency of the dipole. It has been observed that the power goes through the meta-surface and is radiated mainly in boresight direction, which increases the directivity up to 8 dBi and the aperture efficiency of the whole configuration. In the second case, a substrate with the stop band tuned to the pass band of the superstrate and the resonant frequency of the dipole has been added. A directivity higher than 9 dBi with a back radiation of -20 dBi have been obtained.
Open Access
A water content continuous monitoring of grapevine xylem tissue using a portable low-power cost-effective FMCW radar
(IEEE, 2019) Quemada Mayoral, Carlos; García González, Cebrián; Iriarte Galarregui, Juan Carlos; Marín Ederra, Diana; Gastón Beraza, Diego; Miranda Jiménez, Carlos; Gonzalo García, Ramón; Maestrojuán Biurrun, Itziar; Santesteban García, Gonzaga; Ederra Urzainqui, Íñigo; Agronomia, Bioteknologia eta Elikadura; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Agronomía, Biotecnología y Alimentación; Ingeniería Eléctrica, Electrónica y de Comunicación; Gobierno de Navarra / Nafarroako Gobernua, PI025 VITHZ; Gobierno de Navarra / Nafarroako Gobernua, 0011-1365-2016-000084 RAFF
This paper presents the real-time monitoring of a grapevine’s water content that flows up through the xylem tissue by means of a frequency-modulated continuous-wave (FMCW) radar. The application of an optimization process, based on the super-resolution multiple signal classification (MUSIC) algorithm, has enabled the reduction of the bandwidth required to discern the xylem water content, and thus the operating frequency, achieving a depth resolution of at least 3 mm. This design advantage has resulted in a significant step forward towards a real life application, allowing the use of fully-integrated off-the-shelf components in order to implement a completely portable low-power cost-effective radar at 23.1 GHz with a 3.4 GHz bandwidth. The sensor performance has been evaluated by means of three different experiments: irrigation cycles, day/night cycles and comparison between irrigation cycles at different temperatures. From the experimental results, it is possible to assert that the contactless sensor presented in this work is very sensitive to changes in the plant’s water content, differentiating between daytime and nighttime. In addition, it has been proved that temperature has a noticeable influence over the evapotranspiration, observing negative drying slopes of 5.62 mV/cycle and 6.28 mV/cycle at 23ºC and 26ºC respectively.
Open Access
A multipolar analysis of near-field absorption and scattering processes
(IEEE, 2013) Liberal Olleta, Íñigo; Ederra Urzainqui, Íñigo; Gonzalo García, Ramón; Ziolkowski, Richard W.; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
A multipolar formulation is adopted to investigate the absorption and scattering processes involved in near-field interactions. This approach allows one to determine the upper bounds for the absorbed and radiated powers that would be achieved by an ideal lossless sensor, which are of particular interest, for example, to wireless power transfer (WPT), wireless sensors and near-field coupled radiators. The multipolar formulation also helps to extricate the fundamental compromises that must be addressed in the design of such systems, as well as to identify strategies that could approach their best possible performances. The general theory is illustrated with an example consisting of a coated sensor illuminated by a Hertzian dipole, which is a representative example of any scattering or radiating system based on small resonators. The example also serves to compare the performance characteristics obtained with different phenomena such as multipolar resonances, phaseinduced interference effects and cloaking.
Open Access
Fe-rich ferromagnetic wires for self-sensing materials
(IEEE, 2012) Liberal Olleta, Íñigo; Ederra Urzainqui, Íñigo; Gonzalo García, Ramón; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
The possibility of using Fe-rich wires in mechanical stress self-sensing materials is investigated. To this end, a retrieval technique aimed to characterize the high-frequency magnetoimpedance effect in ferromagnetic wires under mechanical stresses is proposed. The technique is based on the measurement of the wires inside a metallic rectangular waveguide, and it is validated through numerical simulations and tested with already published experimental data. In addition, the studied Fe-rich wires are characterized by the occurrence of the natural ferromagnetic resonance, whose frequency position increases from 7 GHz to 8.25 GHz for elongations ranging from 0 μm to 60 μm.
Open Access
Decoupling of multifrequency dipole antenna arrays for microwave imaging applications
(Hindawi Publishing Corporation, 2010) Sáenz Sáinz, Elena; Guven, K.; Ozbay, Ekmel; Ederra Urzainqui, Íñigo; Gonzalo García, Ramón; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
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 planarmetasurface is placed atop the array acting as superstrate. Themutual 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.
Open Access
Least upper bounds of the powers extracted and scattered by bi-anisotropic particles
(IEEE, 2014) Liberal Olleta, Íñigo; Ra'di, Younes; Gonzalo García, Ramón; Ederra Urzainqui, Íñigo; Tretyakov, Sergei A.; Ziolkowski, Richard W.; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
The least upper bounds of the powers extracted and scattered by bi-anisotropic particles are investigated analytically. A rigorous derivation for particles having invertible polarizability tensors is presented, and the particles with singular polarizability tensors that have been reported in the literature are treated explicitly. The analysis concludes that previous upper bounds presented for isotropic particles can be extrapolated to bianisotropic particles. In particular, it is shown that neither nonreciprocal nor magnetoelectric coupling phenomena can further increase those upper bounds on the extracted and scattered powers. The outcomes are illustrated further with approximate circuit model examples of two dipole antennas connected via a generic lossless network.
Open Access
Design of a multifrequency antenna array with the use of left-handed superstrates
(2005) Sáenz Sáinz, Elena; Gonzalo García, Ramón; Ederra Urzainqui, Íñigo; Maagt, Peter de; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
In this paper, the radiation performances of different antenna configuration based on Left-Handed superstrates are presented. First of all, the behaviour of a Left- Handed (LH) unit cell is analysed, showing a resonant response with pass band and stop band frequencies. In order to improve the radiation performances of a single dipole, ie., to increase the directivity and efficiency and to reduce the back radiation, diverse LH superstrates working at the resonant frequency of the dipole are analysed. With these configurations, improvements in terms of directivity higher than 6 dB with efficiency closer to 100 % have been obtained.