Nicolas Ribière-Tharaud

Study of the radiated polarization of an antenna array with circular geometry

This paper deals with an investigation on the polarization of an antenna array with a circular geometry. The theory shows that the polarization of a circular array exhibits a circular polarization independent of the antenna elements. Circular polarization is then achieved whatever the polarization of the elements of the array. Moreover, due to the circular geometry of the array, the entire far field pattern of the array can be obtained with the measurement or the simulation of only one antenna inside the array. The influence of the array radius on the polarization performances has been investigated. An antenna array has been built, and measurements have been performed in order to corroborate the theoretical results.

Multiarms Multiports Externally Fed Spiral Antenna

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.

Design of a spiral antenna with coplanar feeding solution

A new design of spiral antenna is presented in this paper. The shape of the antenna is similar to that of the traditional Archimedean spiral antenna. However, this design allows to feed the antenna on the same plane, which is useful to conform the antenna on various surfaces. Two sources feed the structure. Loads placed along the arms and in the center of the antenna are used to decrease reflections at the end of the arms. Antenna behavior is studied using the software FEKO which is based on method of moments (MoM). This antenna shows the same characteristics as a traditional spiral antenna while being fed outside with coplanar feeding solution. The antenna is studied without a ground plane.

A cavity-backed dual polarized array of connected spiral antennas

A connected array of spiral antennas with dual polarization and backed by a cavity is presented. A 5-elements array is measured using a simple, yet efficient, feeding technique. A low profile cavity is used to make the radiation unidirectional. First measurements show a good agreement between simulations and measurements.

Development of pulsed antennas measurement facility: Near field antennas measurement in time domain

This paper focuses in the construction of a new near-field antenna measurement facility in Electromagnetic Research Department of Supelec dedicated to pulsed antennas characterization. The planar near-field measurement data are exploited through near-field to near-field or near-field to far-field transformation algorithms to determine the antenna radiation pattern in the different spatial areas. The measurement system is described and the results of the experimental validation of the developed algorithms are depicted.

Modeling Broadband Antennas for Hot Electron Bolometers at Terahertz Frequencies

There is a strong need for wideband and sensitive receivers for radio astronomy and remote sensing applications in the terahertz (THz) region. Superconducting hot electron bolometer (HEB) mixers are a competitive alternative to conventional mixer technologies in the THz range. The aim of this chapter is to model antennas coupled to HEBs belonging to an array working in the 1–7 THz range, typically. Several broadband antenna types were investigated before selecting the log-periodic structure. In order to perform experiments in microwave-devoted anechoic chambers, the antenna working frequency band has been scaled down to the 2.25–17.5 GHz range. We have so measured a front-to-side gain ratio of 18 dB at center frequency, which is quite satisfactory for HEB THz imaging arrays. Experimental results performed with scaled models, as compared with simulations performed with a commercially available finite element software, exhibited on the whole good matching within a 2–3 octave bandwidth.

A New Criterion to Jointly Design the Antenna and Optimize the Communication Capacity in IR-UWB

This paper presents the impact of antenna design over the capacity of a IR-UWB system in a Multi-User Interference environment. A new antenna design is proposed and it is showed using a new performance criterion that for this design, the communication capacity given by the Sholtzs pulse might be outperformed by using some other types of pulses. More than that, the proposed criterion might be used in IR-UWB not only to compare the performance of different antennas but also to compare the performance of different pulse shapes from the communication capacity point of view.

Coplanar feeding solution for spiral antenna

A new externally-fed spiral antenna is presented in this paper. This antenna consists of two double arms and two sources in phase opposition are used to feed the device. This new design exhibits characteristics similar to that of the classical two arms center-fed spiral antenna. This is useful to conform the antenna on various platforms that do not allow access to the center of the spiral. The far field pattern is constant and symmetric about the antenna plane over the frequency range. Moreover, when use in an array, the bandwidth of the 2×2 arms spiral antenna is 37.5% larger than to that of the center-fed antenna.

A wideband antenna for P-band airborne SAR applications

A new wideband antenna for airborne SAR applications has been presented. It is based on a geometry that gives a stable phase center. It allows to have a rejection of the ground response ambiguity of more than 34 dB. Its bandwidth (defined for a S11 les -8 dB, with a gain ges 5 dB) is 245-390 MHz (45%). Further works will include the improvement of the S11, along with a size reduction of the LPDA to improve the front to back ratio. Finally, a prototype has to be built.

Front end accordability for cognitive multi-radio, using a class E HPA and a multi-band antenna

In this paper, it has been demonstrated the possibility of frequency discrete shifting with a class E high efficiency PA, simulated with a realistic E-PHEMT model and co-simulated with antenna measures for the load. Antennas loads influence the PA performances because of their wideband characteristic and not only their adaptation at the carrier frequency. This implies a very precise measurement of antenna reflection coefficient for PA co-design. At these frequencies, the transistor packaging can destroy the Class E performance before the loading. Switched PA will show closer performance between simulations and measures if the design is first integrated (longer and costly design). That is why the front end measures are not available yet. Results enable to go further in the methodology of joint-conception between an antenna and a PA for multi-radio. This type of co-design topic demonstrated that in wideband systems, multi-disciplinarity is essential for accurate behaviour of the front-end and performances can target a high efficiency (more than 70 % for the moment) front end in the multi-radio considered bandwidth.