Oscillateur commandé en tension

Résumé

L’oscillateur commandé en tension ou VCO (pour Voltage Controlled Oscillator) est un oscillateur électronique qui émet un signal périodique dont la fréquence se stabilise en fonction de la tension d'entrée. Applications C'est un montage typiquement utilisé dans les boucles à verrouillage de phase. Il permet ainsi de gérer la fréquence de sortie de la boucle de verrouillage, asservie avec la fréquence d'entrée. On retrouve également l'oscillateur commandé en tension en un ou plusieurs exemplaires dans les synthétiseurs analogiques. Pour cette application, la tension qui le commande dépend de la touche appuyée du clavier : la fréquence de l'oscillateur varie donc afin de générer les différentes hauteurs des notes de la gamme musicale. Différents types de VCO Il existe différents types d'oscillateurs commandés en tension, notamment :

les oscillateurs RC ;
l'oscillateur LC avec diode à capacité variable ;
l'oscillateur à YIG (Yttrium Iron Garnet); *Les osci

Source officielle

https://fr.wikipedia.org/wiki/Oscillateur_command%C3%A9_en_tension

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A GSM-GPRS/UMTS FDD-TDD/WLAN 802.11a-b-g multi-standard carrier generation system

Michel Declercq, Adil Koukab, Yu Lei

A compact carrier generation system enabling proper interoperability among quad-band GSM, WCDMA (FDD and TDD), and WLAN (802.11a/b/g) standards is developed. The implementation is achieved in 0.25-mum BiCMOS-SiGe process. The measured tuning range is higher that 1 GHz (3.05 to 4.1 GHz) exceeding the specifications by 25%. The voltage-controlled oscillator (VCO) exhibits a phase noise of -118 and -125 dBc/Hz measured, respectively, at 400 kHz and 1 MHz offsets while drawing 2.5 mA from 2.5 V supply. The measured phase noise at 400 kHz offset of the PCS/DCS output local-oscillator (LO) signal and the GSM output LO signal is, respectively, -124 dBc/Hz and -130 dBc/Hz

2006

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Computing the Impact of White and Flicker Noise in Continuous-Time Integrator-Based ADCs

Paul Stanislas Gosselin, Maher Kayal, Adil Koukab

From first-order incremental Sigma Delta converters to controlled-oscillator-based converters, many ADC architectures are based on the continuous-time integration of the input signal. However, the accuracy of such converters cannot be properly estimated without establishing the impact of noise. In fact, noise is also integrated, resulting in a random error that is added to the measured value. Since drifting phenomena may make simulations and practical measurements unable to ensure long-term reliability of the converters, a theoretical tool is required. This paper presents a solution to compute the standard deviation of the noise-generated error in continuous-time integrator-based ADCs, under the assumption that a previous measure is used to calibrate the system. In addition to produce a realistic case, this assumption allows to handle a theoretical issue that made the problem not properly solvable. The theory is developed, the equations are solved in the cases of pure white noise and pure flicker noise, and the implementation issues implied by the provided formula are addressed.

Ieee2016

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Model-less Measurement-based Computation of Voltage Sensitivities in Unbalanced Electrical Distribution Networks

Mauro Carpita, Konstantina Christakou, Carl Emile Mugnier, Mario Paolone

Within the context of microgrids optimal voltage control, most schemes proposed in the literature either rely on (i) droop-control methods or (ii) methods involving the computation of explicit nodal power set-points as a solution to a given optimization problem. The first category of approaches is in general suboptimal as it relies on locally sensed measurements. The second category guarantees some level of optimality but requires an accurate and up-to-date model of the network that is, in general, not always available in low voltage grids. To overcome the aforementioned limitations, in this work we propose a methodology suitable for voltage control in generic low voltage 3-phase unbalanced grids. It can be used for the computation of either explicit power set-points or to define the droops of local voltage regulators. Its main characteristic is that it does not rely on the knowledge of the system model and its state. In particular, the goal is to compute linearized dependencies between voltage magnitude and nodal power injections, i.e., voltage sensitivity coefficients. The proposed method assumes availability of a monitoring infrastructure and the computation of the desired sensitivities involves the solution of an over-determined system of linear equations constructed solely using available measurements of nodal power injections and voltage magnitudes. The proposed method is also capable to account for the measurement errors and their time correlation. The performance evaluation of the proposed method is carried out using real measurements coming from a real low voltage feeder located in Switzerland equipped with an appropriate metering infrastructure.

Università degli Studi di Genova, Italy2016

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