Design and fabrication of A Ku-band low noise amplifier using FR-4 substrate

The low noise amplifier (LNA) plays an important role in many communication systems, especially at the receiver’s front-ends. In modern RF designs, The LNA is usually fabricated on a microstrip printed circuit board (PCB) due to its simplicity and ability of integrating flexibly with other components in a receiving circuitry unit. At frequencies lower than 6 GHz, the most prevalent substrate material for a microstrip LNA is FR-4 while at higher frequencies of over 10 GHz, it is challenging to design the LNA using this material without causing considerable losses to the RF signal. There are many works related to design microstrip LNA at high frequencies, however, the dielectric substrates used in most of them were high-cost materials for low dielectric loss. This paper introduces an LNA topology using the common, low-cost FR-4 substrate which can be operated in Ku-band for applications such as small satellites’ receivers, with the expected noise figure of lower than 1 dB, gain of around 10 dB and the return loss of around -10 dB. The stepped impedance matching technique has been used for transmission line optimization. The simulated and measured results are presented

Research, design and fabrication of a microwave active filter for nanosatellite’s receiver front-ends at s-band

In satellite technology, the communication between space segment and ground segment plays a vital role in the success of the mission. This paper is targeted at study, design and fabrication of a microwave active filter for the receiver front-ends using coupled line filter structure, which can be applied to the nanosatellite’s communication subsystem. The whole active filter module is a combination of a microstrip bandpass filter and a preceding two-stage wideband low noise amplifier using FET devices. The proposed module operates in the frequency range of 2-2.4 GHz, which can be divided to 10 frequency slots of about 40 MHz for each. These frequency slots will be used for the S-band multi-frequency receiving function of the ground station, as well as the nanosatellite. The simulated and measured results of this active filter configuration are presented

A microwave active filter for nanosatellite’s receiver front-ends at s-bands

In satellite technology, the communication between space segment and ground segment plays a vital role in the success of the mission. This paper is targeted at study, design and fabrication of a microwave active filter for the receiver front-ends using coupled line filter structure, which can be applied to the nanosatellite’s communication subsystem. The whole active filter module is a combination of a microstrip bandpass filter and a preceding two-stage wideband low noise amplifier using FET devices. The proposed module operates in the frequency range of 2 - 2.4 GHz, which can be divided to 10 frequency slots of about 40 MHz for each. These frequency slots will be used for the S-band multi-frequency receiving function of the ground station, as well as the nanosatellite. The simulated and measured results of this active filter configuration are presented

Rhizosphere microbial community in intercropped durum wheat and faba bean as affected by phosphorus fertilizer history

The experiment was conducted in the long term P fertilizer trial of INRA research centre at Auzeville(43.5oN, 1.43oE) in south western France. The three P regimes corresponded to fertilizer levels applied since1968: P0 (no fertilization), P1 (fertilization rate to balance the mean annual P removal by crops) and P4(fertilization rate representing three-­‐ to four-­‐fold that of P1). Durum wheat and faba bean were grown aloneor as durum wheat/faba bean intercrops in this field trial. Their rhizospheres were collected at the faba beanflowering stage, as well as the corresponding bulk soils. Soil DNA and RNA were extracted in these varioussamples and qPCR was used to assess the number of gene copies of fungi, bacteria, as well as several bacterialphyla (Actinobacteria, α-­‐Proteobacteria and Firmicutes (strongly dominated with P-­‐cycling taxa)) and betapropeller phytase (BPP)

Wideband tunable microwave signal generation in a silicon-based optoelectronic oscillator

Si photonics has an immense potential for the development of compact and low-loss opto-electronic oscillators (OEO), with applications in radar and wireless communications. However, current Si OEO have shown a limited performance. Si OEO relying on direct conversion of intensity modulated signals into the microwave domain yield a limited tunability. Wider tunability has been shown by indirect phase-modulation to intensity-modulation conversion, requiring precise control of the phase-modulation. Here, we propose a new approach enabling Si OEOs with wide tunability and direct intensity-modulation to microwave conversion. The microwave signal is created by the beating between an optical source and single sideband modulation signal, selected by an add-drop ring resonator working as an optical bandpass filter. The tunability is achieved by changing the wavelength spacing between the optical source and resonance peak of the resonator. Based on this concept, we experimentally demonstrate microwave signal generation between 6 GHz and 18 GHz, the widest range for a Si-based OEO. Moreover, preliminary results indicate that the proposed Si OEO provides precise refractive index monitoring, with a sensitivity of 94350 GHz RIU and a potential limit of detection of only 10-8 RIU, opening a new route for the implementation of high-performance Si photonic sensors

Étude et réalisation d'un système instrumental de stabilisation d'un modulateur électrooptique (application à l'amélioration du comportement d'un oscillateur optoélectronique)

Les modulateurs electro-optiques (EOM) sont des composants importants dans les systemes de telecommunication. Malheureusement, ils ne sont pas parfaitement stables dans Ie temps et leur fonction de transfert (TF) a tendance a se decaler durant Ie temps d'operation. La derive de la TF d'un EOM peut etre expliquee par des effets differents tels que les changements de la temperature ambiante, de la polarisation ou de l'efficacite de couplage optique. La these presente une methode de me sure de la derive de la TF de I'EOM (a grace d'estimation du comportement non-linearite du modulateur, NLl), et propose deux systemes instrumentaux pour ameliorer son fonctionnement: Ie premier pour contraler la temperature de l'EOM, il est possible de forcement reduire cette derive, Ie deuxieme pour compenser la derive (la stabilisation du point de fonctionnement autour du point quadrature est obtenue jusqu'au 0,22% ou la fluctuation de phase est de 0,44). Ces techniques ont ete aussi appliquees pour ameliorer Ie comportement d'un oscillateur optoelectronique haute frequence. Nous avons realise les experiences par asservissement de temperature, par compensation de la derive. Pour une stabilite de I'OEO a court terme, la stabilisation de la frequence est amelioree jusqu'a 28% en utilisant un contrale de temperature seule etjusqu'a 71 % avec les deux processus. Pour une stabilite de l'OEO a long terme, en deux cas sans contra Ie, I'OEO fonctionne pendant 3 heures et pendant 1,6 heure (puis I'OEO ne marche plus). En utilisant une compensation de la derive de la TF de I'EOM, l'OEO fonctionne bien meme apres 7 heures et 8 heures.Electro-optic modulators (EOM) are important components in telecommunication systems. Unfortunately, there are some physical effects like ambient temperature variations, polarization and inherent photorefractive coefficient which are due to the drift of EOM transfer function (TF). The thesis presents a method for measuring the drift of the TF of EOM (based on a nonlinearity behavior of modulator - NLl), and propose two instrumentation systems to improve their operations: one to control the temperature of EOM, it is possible to significantly reduce the drift, the second to compensate the drift (the bias point stabilization around the quadrature point is obtained up to 0.22% or the phase fluctuation is 0.44). These techniques have been applied to improve the behavior of an optoelectronic oscillator high frequency. Four experiments are carried out by controlling the EOM temperature and by compensating the EOM drift. For a short-term stability of OEO, the stabilization of the frequency is obtained with 28% with using a temperature control, up to 71 % with the two techniques. For a long-term stability of OEO, in cases without any control, the OEO has worked for 3 hours and for 1.6 hours (then, the OEO does not work anymore). By using the drift compensation of the EOM FT, the OEO has correctly worked even more than 7 hours and 8 hours.CACHAN-ENS (940162301) / SudocSudocFranceF

Improving the Behavior of an Electro-Optic Modulator by Controlling Its Temperature

The purpose of this paper is to present the improvement of the stability of an electro-optic modulator obtained from its temperature control. A digital system based on PSOC microcontroller and a small power amplifier has been developed. The behavior of the modulator can be observed by the way of its nonlinear properties. Thanks to the improved thermal stability, it is possible to reduce significantly the drift of the electro-optic modulator

Totémisme

Un siècle de suspicion n’a pas réussi à faire disparaître le mot « totémisme » du vocabulaire des anthropologues. Il ne suffit pas d’éliminer un mot pour se débarrasser d’un problème, même si ce mot n’est plus à la mode et s’il n’est autre chose, à l’origine, qu’un malencontreux contresens fait lors de la traduction de l’expression ojibwa ototeman. Au demeurant, l’expérience historique de l’anthropologie ne manque pas d’exemples de ces rejets qui sont parfois suivis de surprenants retours. Aujourd’hui le vieux débat sur le totémisme ne saurait avoir les mêmes enjeux qu’au début du siècle, quand l’anthropologie cherchait ce qu’il y a de plus primitif dans l’organisation des sociétés comme dans leurs systèmes de croyances