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.
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
Radiation performances of a multifrequency dipole antenna array with a left handed superstrate
(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 a multifrequency antenna array (MFAA) which consists of two dipoles (1 and 3) that are radiating at 9.57 GHz and other one (dipole 2) radiating at 11.98 GHz are presented. In order to improve the directivity and to reduce the coupling between the dipoles, a non-uniform Left Handed (LH) superstrate formed by cells of different resonant frequencies has been placed over them. Each dipole is tuned to the resonant frequency of the cells that are on top of it allowing the power transmission and producing a very uniform illumination that enhance the radiation performances of the whole structure. With this configuration, directivity values of 10.1 dB when dipoles 1 and 3 are radiating and 8.1 dB when dipole 2 is radiating have been obtained, with a gap between dipoles of 0.23 0 at resonant frequency of the first dipole and a coupling smaller than - 17 dB.
Open Access
A dedicated numerical technique for field simulations of antennas on electromagnetic band-gap substrates
(2004) Hon, B.P. de; Beurden, M.C. van; Gonzalo García, Ramón; Martínez Pascual, Beatriz; Ederra Urzainqui, Íñigo; Río Bocio, Carlos del; Azcona, L.; Alderman, B.; Huggard, P.G.; Marchand, L.; Maagt, Peter de; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
Open Access
EBG superstrate antenna for WAAS bands
(2008) Osés de León, Ángel; Iriarte Galarregui, Juan Carlos; Ederra Urzainqui, Íñigo; Gonzalo García, Ramón; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
Multiband antennas can simplify considerably the complexity of receivers and transmitters, reducing the size and the mass of the conventional configurations. On the other hand, applications with high directivity requirements need array designs to comply with the directivity specifications using conventional technology. EBG superstrate designs have been satisfactory applied to single band applications using a single EBG superstrate layer. The number of number of radiating elements of conventional technology designs are considerably reduced when using EBG technology. Dual band configurations have also been designed in a single layer, but when working frequencies are too close a second EBG layer is needed. A dual layer EBG superstrate which can easily be adjusted to the desired operational frequencies is presented. The design has been realized to comply with the navigation antenna requirements of Wide Area Augmentation system (WAAS) application in L1 and L2 bands.
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
Enhancement of the power radiated by a dipole antenna at boresight by means of a left handed superstrate
(IEEE, 2006) Sáenz Sáinz, Elena; Ederra Urzainqui, Íñigo; Gonzalo García, Ramón; Maagt, Peter de; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
In this paper a comparison between the measured radiation performances of a single dipole and a dipole with a left handed superstrate based on a finite periodic repetition of a unit cell is presented. First of all the return losses and resonant frequency of the dipole has been measured for different sizes of the superstrate, having a good impedance matching and a decrease in the resonant frequency as the number of cells increase. By using an anechoic chamber and a receiver horn antenna, the power transmitted at boresight has been measured for different frequencies, observing a filtering behaviour due to the resonant characteristic of the superstrate and an improvement of the power transmitted at the resonant frequency of around 3 dB. Comparing the H and E plane radiation patterns of a dipole and the dipole with superstrate, more symmetrical and directive radiation patterns can be observed. Finally, a comparison between the simulated and measured aperture efficiency is presented with a good agreement.
Open Access
High efficient dipole antennas by using left-handed superstrates
(2004) Sáenz Sáinz, Elena; Gonzalo García, Ramón; Ederra Urzainqui, Íñigo; Maagt, Peter de; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
This paper deals with pass band properties of Left Handed Media (LHM) to enhance dipole antenna performances. The LHM properties have been used in order to make high directivity antennas with good return loss features. The LHM structure is used as superstrate and placed over a dipole antenna. This superstrate is determining the characteristics of radiation patterns. Simulations of different types of LHM configurations are presented. The improvements of the radiation and matching parameters for each configuration are presented. High efficient antennas are obtained with this technique.
Open Access
Enhanced radiation properties of a rectangular waveguide by means of a left handed media
(2005) Sáenz Sáinz, Elena; Ederra Urzainqui, Íñigo; Gonzalo García, Ramón; Maagt, Peter de; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
In this paper, the results of experimental investigations to improve the gain between two antennas by means of a Left Handed Material (LHM) are presented. The basic idea is the use of a LHM media acting as a resonator to concentrate the power radiated by a rectangular waveguide achieving larger directivities and consequently larger gains. The transmission and radiation properties of this metamaterial (MTM) have been measured using a network analyser and two rectangular waveguides in the X band. Comparing the transmission parameter S21 with and without the LHM media between the waveguides, an appreciable improvement in the power received can be observed.
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.