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Contribution à la conception d'un modulateur sigma-delta passe-bande à temps continu pour la conversion directe de signaux radiofréquences

Abstract : The continuous-time bandpass delta-sigma analog-to-digital conversion is an interesting approach for direct conversion of radiofrequencies signals. To go towards fast and reconfigurable conversion systems, the feasibility of a delta-sigma band-pass converter with a tunable central frequency on a limited bandwidth is studied through the design of an integrated circuit in a GaAs P-HEMT technology.
The modulator architecture includes a loop filter, which has a parallel structure to ensure the stability as well as the precision of the device, an adder and a comparator. The loop filter is composed of several Q-enhanced Gm-LC resonators. The optimal delay for this architecture (1:25Te, with Te the sampling period) is approximately reached through a latched comparator (1,12 Te). The adjustment of the central frequency is carried out through one tunable capacity on the front-end resonator.
The transistor level simulation in the nominal case shows a resolution of 10 bits in a useful bandwidth of 4 MHz, for a central frequency of 750 MHz and a 3 GHz sampling frequency. The central frequency of the modulator can be adjusted at 730 MHz where the resolution reaches 9 bits. Consumption is estimated to be 5,7 W. The layout of the chip occupies 12 mm2.
This work presents a design methodology based on multi-level simulations (transistor, functional).
This approach makes it possible to isolate the impact from circuit level non-idealities on the general behaviour of the modulator. Solutions are proposed to correct these drawbacks. The circuit sensitivity was also studied in terms of technological dispersions and parasitic elements introduced by the layout.
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Submitted on : Friday, July 11, 2008 - 11:42:42 AM
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  • HAL Id : tel-00290176, version 2

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Emilie Avignon. Contribution à la conception d'un modulateur sigma-delta passe-bande à temps continu pour la conversion directe de signaux radiofréquences. Micro et nanotechnologies/Microélectronique. Université Pierre et Marie Curie - Paris VI, 2007. Français. ⟨tel-00290176v2⟩

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