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Limoges, France

Demenitroux W.,AMCAD Engineering | Maziere C.,AMCAD Engineering | Gatard E.,AMCAD Engineering | Dellier S.,AMCAD Engineering | And 2 more authors.
IEEE Transactions on Microwave Theory and Techniques

This paper presents a complete validation of the new behavioral model called the multiharmonic Volterra (MHV) model for designing wideband and highly efficient power amplifiers with packaged transistors in computer-aided design (CAD) software. The proposed model topology is based on the principle of the harmonic superposition introduced by the Agilent X-parameters, which is combined with the dynamic Volterra theory to give an MHV model that can handle short-term memory effects. The MHV models of 10-and 100-W packaged GaN transistors have been extracted from time-domain load-pull measurements under continuous wave and pulsed modes, respectively. Both MHV models have been implemented into CAD software to design 10-and 85-W power amplifiers in L-and S-bands. Finally, the first power amplifier exhibited mean measured values of 10-W output power and 65% power-added efficiency over 36% bandwidth centered at 2.2 GHz, while the second one exhibited 85-W output power and 65% drain efficiency over 50% bandwidth centered at 1.6 GHz. © 2012 IEEE. Source

Andrieu G.,Xlim Laboratory | Panh J.,French National Center for Space Studies | Reineix A.,Xlim Laboratory | Pelissou P.,Airbus | And 3 more authors.
IEEE Transactions on Electromagnetic Compatibility

A simple method permitting to obtain a homogeneous panel from a strongly inhomogeneous panel is presented. The method consists of determining the characteristics of a panel having an equivalent conductivity obtained from a near-field magnetic shielding effectiveness measurement. Thus, the method suitable for frequencies lower than 1MHz does not require the knowledge of the detailed internal geometry of the sample. After the validation of the measurement setup on a copper plate of known conductivity, two space composite panels are characterized and homogenized. © 2012 IEEE. Source

Moustafa L.,Xlim Laboratory | Jecko B.,Xlim Laboratory
IEEE Antennas and Wireless Propagation Letters

We have shown in previous works that the use of double-layer frequency selective surface (FSS) in the superstrate of an electromagnetic band-gap (EBG) antenna provides a radiation bandwidth improvement. Nevertheless, such an antenna is still not directive enough for some applications. To increase its gain, the antenna will be fed using the multisource feeding technique. This principle is applied to design a wideband highly directive antenna operating in the Ku-band. When the radiation bandwidth corresponding to the realized gain is equal to 14% for a maximal gain of 22.5 dB, 17% of radiation bandwidth is obtained for a maximal directivity of 23 dB. © 2006 IEEE. Source

Grigoriev Y.G.,Federal Medical Biophysical Center | Grigoriev O.A.,Federal Medical Biophysical Center | Ivanov A.A.,Federal Medical Biophysical Center | Lyaginskaya A.M.,Federal Medical Biophysical Center | And 7 more authors.

This paper presents the results of a replication study performed to investigate earlier Soviet studies conducted between 1974 and 1991 that showed immunological and reproductive effects of long-term low-level exposure of rats to radiofrequency (RF) electromagnetic fields. The early studies were used, in part, for developing exposure standards for the USSR population and thus it was necessary to confirm the Russian findings. In the present study, the conditions of RF exposure were made as similar as possible to those in the earlier experiments: Wistar rats were exposed in the far field to 2450 MHz continuous wave RF fields with an incident power density in the cages of 5 W/m2 for 7 h/day, 5 days/week for a total of 30 days, resulting in a whole-body SAR of 0.16 W/kg. Effects of the exposure on immunological parameters in the brain and liver of rats were evaluated using the complement fixation test (CFT), as in the original studies, and an additional test, the more modern ELISA test. Our results, using CFT and ELISA, partly confirmed the findings of the early studies and indicated possible effects from non-thermal RF exposure on autoimmune processes. The RF exposure resulted in minor increases in formation of antibodies in brain tissue extract and the exposure did not appear to be pathological. In addition, a study was conducted to replicate a previous Soviet study on effects from the injection of blood serum from RF-exposed rats on pregnancy and foetal and offspring development of rats, using a similar animal model and protocol. Our results showed the same general trends as the earlier study, suggesting possible adverse effects of the blood serum from exposed rats on pregnancy and foetal development of intact rats, however, application of these results in developing exposure standards is limited. Copyright © 2010 Wiley-Liss, Inc. Source

Adardour A.,Xlim Laboratory | Andrieu G.,Xlim Laboratory | Reineix A.,Xlim Laboratory
IEEE Transactions on Electromagnetic Compatibility

An original method allowing to define a particular frequency called 'quasi-ideal reverberation chamber (RC) minimum frequency' is presented. This frequency corresponds to the frequency where an RC is considered as working in a 'quasi-ideal regime.' According to the definition of an ideal RC, the method is based on the assessment 1) of the electromagnetic (EM) field distributions obtained in the working volume (in comparison with the distributions obtained in the ideal model defined by Hill [D. A. Hill, 'Plane wave integral representation for fields in reverberation chambers,' IEEE Trans. Electromagn. Compat., vol. 40, no. 3, pp. 209 -217, Aug. 1998.]) and 2) of the number of uncorrelated samples obtained over one mode stirrer revolution. The method is considered as helpful in order to optimize the functioning of an RC at low frequencies for broadband EM compatibility immunity and emission tests. Indeed, it is shown from experimental and numerical results that the insertion of an optimal loading in the chamber allows to decrease the frequency where the chamber works quasi-ideally. The influence of complexifying the mode stirrer geometry is also discussed. © 1964-2012 IEEE. Source

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