Téléphonie par satellite

Résumé

thumb|Trois modèles de téléphones par satellite, de marques Iridium et Thuraya. La téléphonie par satellite est une forme de téléphonie mobile qui relie les utilisateurs entre eux par l’intermédiaire de satellites de télécommunications au lieu d'antennes-relais terrestres. Ce type de télécommunications est utilisé dans des régions où la densité des relais terrestres est insuffisante (régions faiblement peuplées ou inhabitables) ou à bord de bateaux naviguant au large des côtes, hors de portée des antennes relais. Plusieurs techniques peuvent être utilisées pour réaliser un réseau de téléphonie par satellite : celui-ci peut notamment reposer soit sur une constellation de satellites en orbite terrestre basse, moyenne ou en orbite géostationnaire. La téléphonie par satellite apparait à la fin des années 1980 grâce aux progrès de la technologie spatiale et des télécommunications. De nombreux projets de réseau favorisés par la bulle internet sont nés au cours de la deuxième moitié des ann

Source officielle

https://fr.wikipedia.org/wiki/T%C3%A9l%C3%A9phonie_par_satellite

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The main objective of the course is to introduce the concept of space system design and engineering. The course will describe the various subsystems involved in the design of a satellite. It will also describe the techniques of systems engineering that are used to obtain a coherent satellite design.

Bases des références géodésiques, principe de mesure utilisé en localisation par satellites et de l'estimation de la qualité de positions GNSS (Global Navigation Satellites Systems).

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CMOS ASIC Design of Multi-frequency Multi-constellation GNSS Front-ends

Saeed Ghamari

With the emergence of the new global navigation satellite systems (GNSSs) such as Galileo, COMPASS and GLONASS, the US Global Positioning System (GPS) has new competitors. This multiplicity of constellations will offer new services and a much better satellite coverage. Public regulated service (PRS) is one of these new services that Galileo, the first global positioning service under civilian control, will offers. The PRS is a proprietary encrypted navigation designed to be more reliable and robust against jamming and provides premium quality in terms of position and timing and continuity of service, but it requires the use of FEs with extended capabilities. The project that this thesis starts from, aims to develop a dual frequency (E1 and E6) PRS receiver with a focus on a solution for professional applications that combines affordability and robustness. To limit the production cost, the choice of a monolithic design in a multi-purpose 0.18 µm complementary metal-oxide-semiconductor (CMOS) technology have been selected, and to reduce the susceptibility to interference, the targeted receiver is composed of two independent FEs. The first ASIC described here is such FEs bundle. Each FE is composed of a radio frequency (RF) chain that includes a low-noise amplifier (LNA), a quadrature mixer, a frequency synthesizer (FS), two intermediate frequency (IF) filters, two variable-gain amplifiers (VGAs) and two 6-bit flash analog-to-digital converters (ADCs). Each have an IF bandwidth of 50 MHz to accommodate the wide-band PRS signals. The FE achieves a 30 dB of dynamic gain control at each channel. The complete receivers occupies a die area of 11.5 mm2 while consuming 115 mW from a supply of a 1.8 V. The second ASIC that targets civilian applications, is a reconfigurable single-channel FE that permits to exploit the interoperability among GNSSs. The FE can operate in two modes: a ¿narrow-band mode¿, dedicated to Beidou-B1 with an IF bandwidth of 8 MHz, and a ¿wide-band mode¿ with an IF bandwidth of 23 MHz, which can accommodate simultaneous reception of Beidou-B1/GPS-L1/Galileo-E1. These two modes consumes respectively 22.85 mA and 28.45 mA from a 1.8 V supply. Developed with the best linearity in mind, the FE shows very good linearity with an input-referred 1 dB compression point (IP1dB) of better than -27.6 dBm. The FE gain is stepwise flexible from 39 dB and to a maximum of 58 dB. The complete FE occupies a die area of only 2.6 mm2 in a 0.18 µm CMOS. To also accommodate the wide-band PRS signals in the IF section of the FE, a highly selective wide-tuning-range 4th-order Gm-C elliptic low-pass filter is used. It features an innovative continuous tuning circuit that adjusts the bias current of the Gm cell¿s input stage to control the cutoff frequency. With this circuit, the power consumption is proportional to the cutoff frequency thus the power efficiency is achieved while keeping the linearity near constant. Thanks to a Gm switching technique, which permit to keep the signal path switchless, the filter shows an extended tuning of the cutoff frequency that covers continuously a range from 7.4 MHz to 27.4 MHz. Moreover the abrupt roll-off of up to 66 dB/octave, can mitigate out-of-band interference. The filter consumes 2.1 mA and 7.5 mA at its lowest and highest cutoff frequencies respectively, and its active area occupies, 0.23 mm2. It achieves a high input-referred third-order intercept point (IIP3) of up to -1.3 dBVRMS.

EPFL2016

Chargement

In this paper, we analyze Orthogonal Frequency-Division Multiple Access and Single-Carrier Frequency Division Multiple Access as alternative physical layer schemes for the up-link of a satellite network. Both orthogonal frequency-division multiple access and single-carrier frequency division multiple access are orthogonal multicarrier modulations (MCMs). They provide a higher spectral efficiency than the single-carrier modulations employed today in satellite networks. Unfortunately, MCMs are also more vulnerable to nonlinear distortion, phase noise, and synchronization errors. This has prevented, so far, the use of MCMs in satellite uplinks, where these impairments are very critical. In our analysis, we show that a well-design MCM system can effectively provide reliable communications in satellite uplinks, even in the presence of nonlinear distortion, phase noise, and synchronization errors. Copyright (C) 2014 John Wiley & Sons, Ltd.

Wiley-Blackwell2014

Chargement

CMOS ASIC Design of Multi-frequency Multi-constellation GNSS Front-ends

Saeed Ghamari

EPFL2016