Nouvelle topologie de déphaseurs analogiques agiles large bande

National audienceUn nouveau type de déphaseur analogique à variation continue de phase est présenté. Il est basé sur l'association du déphaseur de Schiffman et de varicaps assurant l'agilité en phase. Cette topologie assure un nouveau compromis particulièrement intéressant en terme de bande passante, de plage de variation de phase, de pertes d'insertion, de compacité et de coût. L'application principale visée est le réseau d'antennes à balayage. Un prototype à une seule cellule a été conçue sur la bande 4-7 GHz. La validation expérimentale montre un très bon accord avec la simulation avec une agilité en phase de plus de 180° et permet d'envisager les 360° avec seulement deux cellules, tout en assurant un niveau de pertes d'insertion très raisonnable pour un déphaseur analogique

An All-Pass Topology to Design a 0-360° Continuous Phase Shifter with Low Insertion Loss and Constant Differential Phase Shift

International audienceIn this paper, an analog phase shifter is designed by using a novel all-pass topology. The phase shift can be continuously adjusted from 0 up to 380° by biasing varactor-diodes while maintaining the differential phase shift constant across the 6.7 GHz - 7.7 GHz band. This two-stage circuit is simple and compact with respectively insertion losses of 2.9 dB +- 1.3 dB, return losses better than 9.4 dB and a differential phase shift flatness of +- 11° in the worst case. With a 90.5°/dB Figure-of-Merit, this topology presents an interesting trade-off between low-cost, low loss, large phase-shift range, phase flatness and bandwidth. Measurements are discussed and carefully compared to current competing topologies

Nouveau déphaseur variable analogique large-bande

National audienceDans cet article, une nouvelle topologie de déphaseur analogique variable est proposée. Elle est obtenue en inter-combinant un déphaseur de Schiffman et un déphaseur passe-tout mixte distribué/localisé. Ce déphaseur compact présente l'avantage d'une forte agilité en phase pour une variation limitée de la capacité de la varicap. Les mesures du dispositif réalisé en technologie hybride microruban confirme une variation continue du déphasage jusqu'à 180° pour un circuit à une seule cellule. Sur l'ensemble de la bande considérée, i.e. 4-7 GHz, les pertes d'insertion sont à 1,8 dB+- 1 dB. Cette topologie présente un compromis entre plage de variation, compacité, pertes, platitude de phase particulièrement intéressant

Simple and accurate quantification of BTEX in ambient air by SPME and GC–MS

Benzene, toluene, ethylbenzene and xylenes (BTEX) comprise one of the most ubiquitous and hazardous groups of ambient air pollutants of concern. Application of standard analytical methods for quantification of BTEX is limited by the complexity of sampling and sample preparation equipment, and budget requirements. Methods based on SPME represent simpler alternative, but still require complex calibration procedures. The objective of this research was to develop a simpler, low-budget, and accurate method for quantification of BTEX in ambient air based on SPME and GC–MS. Standard 20-mL headspace vials were used for field air sampling and calibration. To avoid challenges with obtaining and working with ‘zero’ air, slope factors of external standard calibration were determined using standard addition and inherently polluted lab air. For polydimethylsiloxane (PDMS) fiber, differences between the slope factors of calibration plots obtained using lab and outdoor air were below 14%. PDMS fiber provided higher precision during calibration while the use of Carboxen/PDMS fiber resulted in lower detection limits for benzene and toluene. To provide sufficient accuracy, the use of 20 mL vials requires triplicate sampling and analysis. The method was successfully applied for analysis of 108 ambient air samples from Almaty, Kazakhstan. Average concentrations of benzene, toluene, ethylbenzene and o-xylene were 53, 57, 11 and 14 µg m−3, respectively. The developed method can be modified for further quantification of a wider range of volatile organic compounds in air. In addition, the new method is amenable to automation

Monitoring of Ionosphere Propagation Conditions using Opportunistic HF Signals

International audienceThe ionosphere refers to the upper regions of the atmosphere (90 to 1000 km). This region is highly ionized, that is, it has a high density of free electrons (negative charges) and positively charged ions. It has practical importance because, among other functions, it enables HF radio propagation to distant places on the earth. The ionization of neutral atoms is mainly due to the extreme ultraviolet light radiation from the sun. Consequently, the ionosphere exhibits diurnal changes (day / night), seasonal changes (summer / winter) and is strongly affected by solar activity (11-year cycle, solar flares, ...). Knowledge of the characteristics of the ionosphere is required to establish radio communication links over large distances around the globe. We present in this paper the use of opportunistic HF waves in order to obtain information on the state and variation of the ionosphere. Once HF signals are identified, the knowledge of their characteristic (power, signal path, …) will allow us to study the state and the behavior of the ionosphere. The work of this paper is a first step in a research project that aims for environmental monitoring for ionospheric propagation

Utilisation de la méthode des plans d'expériences pour l'optimisation d'un résonateur microruban

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Déphaseur 360 ° compact large-bande

National audienceCet article présente un déphaseur analogique 0-360 ° à variation continue de phase dans la bande 6,7 GHz - 7,7 GHz. La variation en phase est assurée par des varactors. La topologie de la cellule élémentaire est particulièrement simple et compacte. Les 360 ° sont atteints avec seulement deux cellules avec un minimum de composants pour assurer la polarisation. Le démonstrateur hybride présente des pertes d'insertion de 2,9 dB +- 1,3 dB, une adaptation meilleure que 9,4 dB, un déphasage différentiel de platitude +- 11 ° et un Facteur de Mérite de 90,5 °/ dB

Tunable Channelized Bandstop Passive Filter Using Reconfigurable Phase Shifter

International audienceA novel tunable channelized two-branches passive bandstop filter using a reconfigurable parallel-coupled-line-based Phase Shifter (PS) is presented. The filter topology uses the signal destructive principle and aims to protect the receiver against an unwanted interference signal received by the antenna. The global filter topology contains two branches, each of which has a different function. The bandpass tunable branch selects the frequency to be rejected while the reconfigurable PS plays the signal invertor role. The simultaneous tunability of both bandpass and PS branches is ensured by using identical varactor diodes and features 550-700 MHz tuning range. In addition of having a constant and relatively high rejection level over all the tuning range and low insertion loss in the passband area, the filter guaranties ultra-low power consumption. Moreover, synthesis equations are proposed and used to illustrate the operating principle, and finally validated by comparing simulations results to measurements

Nanomedicine Strategies for Management of Drug Resistance in Lung Cancer

Lung cancer (LC) is one of the leading causes of cancer occurrence and mortality worldwide. Treatment of patients with advanced and metastatic LC presents a significant challenge, as malignant cells use different mechanisms to resist chemotherapy. Drug resistance (DR) is a complex process that occurs due to a variety of genetic and acquired factors. Identifying the mechanisms underlying DR in LC patients and possible therapeutic alternatives for more efficient therapy is a central goal of LC research. Advances in nanotechnology resulted in the development of targeted and multifunctional nanoscale drug constructs. The possible modulation of the components of nanomedicine, their surface functionalization, and the encapsulation of various active therapeutics provide promising tools to bypass crucial biological barriers. These attributes enhance the delivery of multiple therapeutic agents directly to the tumor microenvironment (TME), resulting in reversal of LC resistance to anticancer treatment. This review provides a broad framework for understanding the different molecular mechanisms of DR in lung cancer, presents novel nanomedicine therapeutics aimed at improving the efficacy of treatment of various forms of resistant LC; outlines current challenges in using nanotechnology for reversing DR; and discusses the future directions for the clinical application of nanomedicine in the management of LC resistance

A Shape optimization library for the design of microwave components

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