Search

International audience; 4-arm spiral antennas have a wide bandwidth and circular polarization when operating in mode 1 (fundamental mode). Switching to mode 3 (to obtain opposite circular polarization) dramatically reduces the antenna bandwidth compared to mode 1. In this work we reduce the arm sizes of the spiral (for example with RF switches) to increase the bandwidth of mode 3 at the higher mode 1 frequencies. In this way the antenna has the same wide bandwidth for both polarizations (modes).

International audience; This article presents a high-efficiency dual-band rectenna, for RF energy harvesting in GSM bands (900-1800 MHz).The rectifier used is a dual-diode rectifier topology based on a Delon voltage doubler. To ensure, the highest efficiency as possible, source-pull simulations are used to determine the optimal diodes input impedance. The antenna is a spiral planar structure, where two slots ring resonators have been added to expand bandwidth at low frequencies without increasing its initial size. It is associated with a broadband balun to transform its impedance into the desired 50-Ω rectifier input impedance. The antenna and balun are sized for broadband operation to cover the main wireless communication bands. Measurement results show high RF-DC conversion efficiencies of 28% and 20% at 890 MHz and 1780 MHz, respectively,for a low RF input power of −20 dBm and with a 10 kΩ DC load. Efficiency reaches 43.5% with a dual-tone signal at −20 dBm.

International audience; A planar array of symmetrical square spiral antennas over a ground plane have resonances when scanning off-broadside. This paper demonstrates that resonances also appear in a single symmetrical receiving spiral antenna without a ground plane, provided that the incident wave is off-broadside. Transmission line analysis predicts the resonances.

International audience; A circularly polarized wideband omnidirectional array of spiral antennas is presented. It covers the frequency band from 1.2 GHz up to 3.6 GHz while keeping a good S11 and an omnidirectional coverage. This array achieved a dual polarization using left and right hands archimedean spiral antennas. The gain of the array is enhanced using a unique cavity for the entire array and the realized gain is above the maximum theoretical gain of a single spiral antenna.

International audience; An analytical method to estimate the bandwidth of planar phased array of spiral antennas is presented. Three main parameters are considered: circular polarization, reflection coefficient and sidelobe levels. An application of the method for a planar array of asymmetrical Archimedean spirals is presented for a scan angle of = 30 ???. The estimated bandwidth and the bandwidth obtained with the simulation results differ in 3.5%

International audience; A wideband dual-polarization, low-profile cavity backed four-arm Archimedean spiral antenna is first presented. This is further extended to a linear array of spiral antennas. Beamforming capability of the linear array for both polarizations is measured and presented for a 4:1 bandwidth.

International audience; A wideband dual-circular unidirectional four-arm Archimedean spiral antenna operating from 0.6 to 2.4 GHz is presented. Without a cavity, the antenna radiates bi-directionally and the dual-circular polarisation of the spiral antenna at boresight is limited to a frequency range from 0.6 to 1.5 GHz. After adding a low-profile, 15 mm deep metallic cavity, the dual-circular polarisation at boresight is extended to more than 2.4 GHz and uni-directional radiation is realised. The four-arm spiral antenna is excited through a feed network consisting of a wideband four-way power divider and four wideband digital 2-bit phase shifters. This feed network facilitates instantaneous switching between right hand circular polarisation and left hand circular polarisation. The measured input return loss of the system is more than 10 dB for the entire two-octave bandwidth. The measured boresight gain from 0.6 to 2.4 GHz is −2.8 to 11.2 dBi and −3.1 to 8.7 dBi for RHCP and LHCP, respectively.

International audience; The design of a wide bandwidth dual-polarized phased array of Archimedean spiral antennas with cavity is presented. The reflection coefficient, circular polarization and grating lobes are addressed independently in the design process. Uniform concentric rings array is used to control the grating lobes, thanks to its non uniform spatial distribution, and obtain a good circular polarization, thanks to its rotational symmetry. Simulations of one-ring array agree with the measurements. Adding more rings keeps the side lobes level to less than -10 dB, relative to the main lobe. The dual-polarized array can scan up to θ = 30° keeping a low reflection coefficient and low side lobe levels.

International audience; This letter focuses on the experimental validation of a new square spiral antenna topology. The proposed topology can operate over an ultrawideband and be reconfigured into an array of smaller square spiral antennas. This offers a good surface efficiency and many advantages like an increase of both gain and directivity, a good circular polarization over the entire bandwidth, and the ability to reconfigure the radiation pattern. In the letter, the experimental validation is given for frozen states.

This work focuses on the design of wideband dual polarized arrays using spiral antennas. These antennas are known for having wideband properties. But, due to the presence of the grating lobes, the bandwidth is decreased when using an array instead of a single antenna. In order to obtain a dual polarized array, it is needed to use elements of opposite polarization, which creates great distances between same polarization elements, meaning an earlier presence of the grating lobes. In this work, an analytic method was developed to estimate the bandwidth of the spiral arrays. This method showed that the maximum bandwidth of uniform spiral arrays is about an octave, for the mono-polarized case, and nonexistent for the dual polarized case. Working on the validation of the method, some resonances were observed. Explanations are presented, as well as possible solutions. Trying to expand the bandwidth of the array, it was found that it is possible and suitable to use at the same time the two current design paradigms for wideband arrays. Using this idea, a 6:1 bandwidth concentric rings array using connected spirals was achieved. Perspectives are also presented.; Ce travail porte sur la conception de réseaux large bande à double polarisation basées sur des antennes spirales d'Archimède. Ces antennes sont connues pour avoir une bande passante très large. Mais, dans un réseau, la bande passante est diminuée du fait de l'apparition de lobes de réseaux. Pour que le réseau fonctionne à double polarisation, il est nécessaire d'utiliser des éléments de polarisations opposées, ce qui accroit encore la distance entre les éléments possédant la même polarisation. Ceci fait ainsi apparaître les lobes de réseaux à des fréquences inférieures par rapport au cas à mono polarisation. Dans ce travail, une méthode analytique a été développée pour estimer la bande passante des réseaux d'antennes spirales. Cette méthode a montré que la bande passante maximale d'un réseau à distribution spatiale uniforme est d'environ une octave pour le cas à mono polarisation et inexistant pour le cas à double polarisation. Pendant la validation de la méthode d'estimation quelques résonances ont été observées. Des explications de ce phénomène sont présentées, ainsi que des possibles solutions. Pour élargir la bande passante du réseau, nous montrons qu'il est possible d'utiliser en même temps les deux tendances actuelles de conception de réseaux d'antennes large bande. En utilisant deux techniques issues de ces deux tendances, nous avons pu réaliser un réseau présentant une bande passante de 6:1. Des perspectives sont aussi présentées.

This work focuses on the design of wideband dual polarized arrays using spiral antennas. These antennas are known for having wideband properties. But, due to the presence of the grating lobes, the bandwidth is decreased when using an array instead of a single antenna. In order to obtain a dual polarized array, it is needed to use elements of opposite polarization, which creates great distances between same polarization elements, meaning an earlier presence of the grating lobes. In this work, an analytic method was developed to estimate the bandwidth of the spiral arrays. This method showed that the maximum bandwidth of uniform spiral arrays is about an octave, for the mono-polarized case, and nonexistent for the dual polarized case. Working on the validation of the method, some resonances were observed. Explanations are presented, as well as possible solutions. Trying to expand the bandwidth of the array, it was found that it is possible and suitable to use at the same time the two current design paradigms for wideband arrays. Using this idea, a 6:1 bandwidth concentric rings array using connected spirals was achieved. Perspectives are also presented., Ce travail porte sur la conception de réseaux large bande à double polarisation basées sur des antennes spirales d'Archimède. Ces antennes sont connues pour avoir une bande passante très large. Mais, dans un réseau, la bande passante est diminuée du fait de l'apparition de lobes de réseaux. Pour que le réseau fonctionne à double polarisation, il est nécessaire d'utiliser des éléments de polarisations opposées, ce qui accroit encore la distance entre les éléments possédant la même polarisation. Ceci fait ainsi apparaître les lobes de réseaux à des fréquences inférieures par rapport au cas à mono polarisation. Dans ce travail, une méthode analytique a été développée pour estimer la bande passante des réseaux d'antennes spirales. Cette méthode a montré que la bande passante maximale d'un réseau à distribution spatiale uniforme est d'environ une octave pour le cas à mono polarisation et inexistant pour le cas à double polarisation. Pendant la validation de la méthode d'estimation quelques résonances ont été observées. Des explications de ce phénomène sont présentées, ainsi que des possibles solutions. Pour élargir la bande passante du réseau, nous montrons qu'il est possible d'utiliser en même temps les deux tendances actuelles de conception de réseaux d'antennes large bande. En utilisant deux techniques issues de ces deux tendances, nous avons pu réaliser un réseau présentant une bande passante de 6:1. Des perspectives sont aussi présentées.

This paper presents a method to improve the circular polarization of an Archimedean spiral antenna placed over a radial Artificial Magnetic Conductor (AMC). Results have been compared with the same radiating element over a more classical AMC reflector. A prototype of an Archimedean two-wire spiral antenna has been built to operate from 0.5 GHz to 6 GHz. Measurement results with this radial AMC give a relative bandwidth of 79 %, in which the broadside RHCP gain is improved. In this bandwidth the axial ratio of Archimedean spiral antenna placed over a radial AMC is less than 2 dB whereas it is higher than 3 dB with a classical cartesian shape of AMC reflector.

International audience; This letter deals with an externally fed spiral antenna. This design is a slot antenna that exhibits a behavior similar to that of the center-fed Archimedean spiral antenna with an improvement in terms of polarization. The antenna radiates a circular polarization over a wide frequency band within a wide angular range. Moreover, the polarization radiated can be right/left circular or linear vertical/horizontal. A prototype has been manufactured and compared to the modeled antenna. Good agreement is shown between measurement and simulation results.

International audience; A technique is presented to design dual polarization spiral antenna phased arrays using mono polarization spirals in an alternating configuration. The proposed technique consists of connecting cross polarized neighboring spirals. Thus, the currents in the arms of one spiral flow into the arms of the adjacent spirals. In addition, the currents transmitted to the neighboring spirals radiate the same polarization, as a center fed spiral and an externally fed cross spiral radiate the same polarization. The optimization of the shape of the connection is also presented. The lowest operating frequency of the new array design is 1.8 times lower than an array of isolated spirals while being dual polarized and steerable .

In this thesis, original solutions are proposed for antennas not sensitive to their environment. These antennas are designed for GNSS applications and more precisely for multi-bands ones. So the solutions are developed keeping in mind the GNSS specifications. Two difierent research axis are discussed. The first one deals with the natural properties of an antenna composed of diferent radiating structures. So an helix structure is associated with a metallic plate. The specifications of this antenna are in line with the ones of commercial antennas. Nevertheless, this antenna is only one band and in linear polarization which is not conform to the GNSS specifications. To satisfy these specifications a second axis is developed. In this second axis an electric antenna is associated with a specific reflector : a High Impendance Surface. Theorically, this surface allows to place the antenna very close and so reduce the thickness of the whole structure without disturbing the radiation of the antenna. Firstly, the High Impendance Surface and more precisely its periodic patterns is studied. Both one band and dual-band pattern are designed. The one band pattern has a good bandwidth (13%) compared to its size (2,5mm). The dual-band pattern designed by pattern enclosing realized the GNSS specifications in simulation. This is followed by measures. The aim of the thesis is to place the antenna above the designed HIS so a lot of antennas are designed to test and tune the surface. Firstly dipoles are used to study the coupling effects and secondly circular polarized antenna are used to reach the GNSS specifications. For both axis, the radiation pattern and the size of the whole system is optimized. So the proposed solutions are the thinest ones. To conclude the caracteristics of the proposed structures are compared to specifications and to existing antennas and futur work is proposed.; Nous proposons d'explorer dans le cadre de la thèse des solutions originales permettant d'obtenir des caractéristiques de rayonnement peu dépendantes du support de l'antenne. Les antennes étudiées et conçues visent à être utilisées pour des applications GNSS et plus précisément pour des applications multi-bandes du GNSS. Nous les développerons donc en respectant un cahier des charges associé. Deux axes de recherche indépendants sont explorés. Le premier montre les propriétés naturelles d'une antenne composée de plusieurs structures rayonnantes. Nous associons ainsi une structure hélicoïdale équivalente à un dipôle magnétique et un plan métallique équivalent à un dipôle électrique. La taille et les performances de l'antenne ainsi réalis ée sont comparables par bien des aspects aux antennes que l'on trouve actuellement dans le commerce pour les applications GNSS. L'antenne réalisée est une antenne mono-bande en polarisation rectiligne ; ce qui n'est pas en accord avec les spécifications de l'application envisagée. Pour compléter cette première étude et satisfaire les exigences d'applications GNSS multi-bandes, nous nous orientons vers une autre technologie qui est exposé dans le second axe. Dans le second axe, nous associons une antenne électrique et un plan ré ecteur particulier : une Surface Haute Impédance. L'association de ces deux éléments permet en théorie de réduire l'épaisseur qu'aurait un dispositif classique composé d'une antenne électrique et d'un plan réflecteur métallique. Nous commençons donc par étudier la particularité du plan réflecteur choisi, c'est-à-dire la Surface Haute Impédance. Cette surface étant composé de motifs périodiques nous étudierons le motif qui permet d'obtenir les caractéristiques les plus proches de celles de l'application visée. Nous débutons par une étude en monobande suivi de l'étude d 'un motif bi-bande. Le motif mono-bande conçu en simulation présente une très bonne bande-passante (13%) au vue de sa taille minimale (2,5mm). Le motif bi-bande réalisé par imbrication de motifs mono-bande permet d'obtenir en simulation des performances conformes aux attentes dans deux bandes GNSS choisies. L'étude de cette surface se poursuit par une phase de mesure. Le but de l'étude étant de pouvoir placer une antenne au-dessus de la surface fabriquée, une collection d'antennes sera développée afin de régler la surface haute impédance et dans le même temps de tester le dispositif complet. Ainsi dans un premier temps, nous utiliserons des dipôles pour tester et régler la Surface Haute Impédance. Dans cette partie le couplage entre l'antenne et la surface haute impédance placée en-dessous sera notamment étudié. Dans un deuxième temps, afin d'obtenir une polarisation circulaire nous utiliserons d'autres antennes supportant cette polarisation (dipôle croisé et spirale). Dans chaque phase de mesure, le réglage antenne et Surface Haute Impédance sera optimisé et divers paramètres de réglage seront identifiés. Pour les deux axes de recherche, ce sont non seulement le rayonnement que nous cherchons à maîtriser mais aussi la taille de la structure. Ainsi les structures réalisées sont les plus compactes possibles surtout en terme de finesse. Nous concluons sur les performances des antennes réalisées par rapport au cahier des charges et aux autres antennes existantes et exposons les perspectives du travail réalisé.

International audience; A low profile and dual-band High Inpedance Surface to be used as a Artificial Magnetic Conductor for a GPS antenna is presented here. The two bands designed compelete in simulation and in measure the GNSS characteristics.

International audience; A spiral antenna is a broadband element exhibiting circular polarization: right-hand circularly polarized (RHCP) or left hand circularly polarized (LHCP) depending on its winding. An array of spirals with dual polarization must therefore have spirals winding both right and left. A simple configuration alternates every other RHCP element with a LHCP element. In that case, the spacing is such that the frequency at which the grating lobes appear (so the maximum frequency of the array) is lower than the minimum frequency of the spiral (and, so, of the array, with a return loss less than −10dB).

International audience; Spiral antennas are usually fed in the center by a balanced signal. However, in some configurations, it is not always possible to feed the antenna in the center. In this paper, an externally-fed spiral antenna is studied. The antenna exhibits characteristics similar to that of the center-fed spiral antenna with an improvement in terms of polarization.

NUMÉRO SPÉCIAL ANR; International audience; The CIMPA Project (2007-2008), led under the ANR-TECSAN Call, was coordinated by SENSeOR, in partnership with the LEAT and the FEMTO. The aim of the project was to develop a surface acoustic wave sensor demonstrator, passive implantable to monitoring the blood pressure and the temperature. This sensor uses the surface acoustic wave technology (SAW) and is composed of three resonators using quartz as piezoelectric substrate. One resonator for temperature measurement (T), a second resonator for the blood pressure measurement (P) and a third resonator, which is used as reference (R). This sensor is compatible with size requirements inherent to an implantation in an artery, since the size of the resonator with its antennas in its most compact configuration is of the order of 5.2mm×3.7mm×0.85mm. It requires no embarked sources of energy and being able to be interrogated by a radiofréquence (RF) connection thanks to a transceiver, which emits a signal in the band industrial, scientific and medical (ISM). The sensor (connected to an integrated antenna on quartz of very small dimension) requested by the signal of interrogation emits in its turn a signal, which carries information of pressure and temperature. The transceiver then collects apart from its transmitting phase the signal emitted by the sensor and extracts by an appropriate signal processing method information of pressure and temperature. The targeted range for pressure measurement extends from 1bar to 1.35bar with an accuracy of about 2% FS.; Le projet CIMPA (2007–2008), réalisé dans le cadre de l’appel ANR-TECSAN, a été coordonné par SENSeOR, en partenariat avec le LEAT et le FEMTO. Son objectif était la mise au point d’un démonstrateur de capteur surface acoustic waves (SAW) passif, implantable, permettant de mesurer la pression artérielle ainsi que la température. Ce capteur utilise la technologie des ondes acoustiques de surface (SAW) et est composé de trois résonateurs sur quartz. Un premier résonateur pour la mesure de température (T), un second résonateur pour la mesure de la pression sanguine (P) et un troisième résonateur qui sert de référence (R). Ce capteur est compatible des exigences d’encombrement inhérentes à une implantation dans une artère puisque la taille du résonateur avec ses antennes, dans sa configuration la plus compacte, est de l’ordre 5,2 mm × 3,7 mm × 0,85 mm. Il ne nécessite aucune source d’énergie embarquée et peut être interrogé via une liaison radiofréquence (RF) grâce à un interrogateur qui émet un signal dans la bande industriel, scientifique et médical (ISM). Le capteur sollicité par le signal d’interrogation, via son antenne intégrée de très petite dimension, émet à son tour un signal qui porte les informations de pression et de température vues par ce dernier. L’interrogateur capte alors le signal émis par le capteur et en extrait, via un traitement du signal adapté, les informations de pression et de température. La gamme de mesure de pression s’étend de 1 bar à 1,35 bar avec une précision de l’ordre de 2 %.

International audience; A technique to design dual polarization spiral antenna phased arrays using mono polarization spirals is presented. The proposed technique consists of two interleaved subarrays, one for each polarization. The position of every spiral antenna is optimized through a genetic algorithm so that each array is nearly the size of the platform while having low sidelobes. Both resulting arrays have the same properties and are steerable. This method also helps to increase the bandwidth. An 80-element spiral array (spiral of width 0.25 m) with dual polarization is demonstrated, its beam can be steered ±30°, over almost one octave (1.97:1). The physical rejection of the sidelobes (i.e., without weighting) is about - 10 dB.

International audience; In this paper, we presented a new technique to optimize a human implanted spiral antenna for a 2.45GHz wireless temperature and pressure SAW sensor system. The antenna was designed to especially operate when closely implanted to a human heart. In a homogenous phantom, we have shown that it was possible to simply link the two arms of a traditional dipole to achieve better matching and reduced antenna’s dimensions.

International audience; The performance of a dual-arm millimeter wave Archimedean spiral antenna integrated on SOI is described. The impact of the feeding structure on the return loss and the axial ratio is displayed. A good return loss with 35 GHz -10 dB bandwidth and good circular polarization over 120° elevation angle independent on the azimuth angle (less than -5 dB axial ratio) are obtained. The simulated efficiency is 80 % with a gain of 4.3 dBi.

International audience; A new way to design dual polarization wideband spiral antenna array is presented. The proposed technique consists of two interleaved arrays, one for each polarization. The position of every spiral antenna is optimized through a genetic algorithm so that each array is nearly the size of the platform while having low sidelobes. Both resulting arrays have the same properties and are steerable. This method also helps to increase the bandwidth. A 200-elements spiral array (spiral of width 0.25m) with dual polarization is shown, its beam can be steered ±30°, over more than two octaves (2.36:1). The physical rejection of the sidelobes (i.e. without weighting) is about -10 dB. The planar extension is also introduced.

International audience; This paper describes the performance of a coherent homodyne spectrometer to preserve phase information of the THz electric field. Thereby, optical constants of a high resistive silicon sample are presented between 200 GHz and 1.2 THz. The phase shift introduced by such a thick sample is much greater than 2π, and the manner of solving the ambiguity of the modulo 2π is discussed and can be used to surround the refractive index mainly at high frequency where the signal to noise ratio decreases. The analysis of the coherent homodyne signal as a function as the frequency at a fixed delay line permits deduction of sample thickness or measurement of distance without any mechanical displacement, and so facilitates potential ranging and tomography studies.

We demonstrate a high-spectral-purity continuous-wave terahertz source, using a diode pumped Yb3+:CaF2 dual frequency laser. THz radiation is generated by photomixing the two frequencies in a low-temperature grown In. 23Ga. 77As photoconductor, doped with Be, and loading a spiral antenna. The frequency difference between the two optical modes is tuneable by step from d. c. to 2 THz. A maximum laser power of 215 mW CW has been obtained with a beatnote-linewidth narrower than 30 kHz. Measurements show a tuneable THz emission with a maximum output power in the order of few tens nW.