Systèmes de numérisation hautes performances à base de modulateurs sigma delta passe-bande

Abstract : Mobile Communication systems tend to integrate more and more applications (GSM, radio, TV, GPS, etc.) and different standards (GSM, UMTS, WIMAX,..). This evolution requires a flexible receiver able, with a single channel, to deal with each different standard and application. The principle of such a receiver is based on the concept of the Software Radio. The basic idea of the software radio is to integrate the analog-to-digital converter in the channel receiver directly after the antenna. This allows the receiver to adapt itself to different standards by reprogramming the functionality of all digital components in the channel receiver. However, the current standard communications require high flow, so the useful signal frequency bands must be extended (up to several hundred megahertz). Therefor, the A/D bandwidth must be expanded. One way to meet these requirements is the use of analog-to-digital converters based on parallel sigma-delta modulators. Three architectures were proposed on the state of the art based on this principle : Time Interleaved Sigma-Delta, Parallel Sigma-Delta based on Hadamard modulation and Frequency Band Decomposition (FBD). These architectures convert the entire frequency band. However, for multistandard applications, a useful signal has a limited bandwidth and thus the conversion of the entire frequency band is not optimal. This thesis proposes a new architecture for bandpass A/D converter using parallel band pass sigma-delta modulator based on the principle of the frequency band decomposition. We have used continuous time modulators to reach the high operating frequency. Moreover, a digital reconstruction system was proposed to reconstruct the digital input signal using all modulators output. Technological dispersions on analog components decrease considerably the expected resolution of the converter. Actually, they shift resonator central frequencies of the modulator from their nominal value. This leads to mismatch the digital reconstruction system already calibrated to work with nominal values. In order to overcome this problem, the idea is to extend the usual FBD architecture by adding two additional modulators (EFBD Extended Frequency Band Decomposition). The EFBD architecture allows a 5% relative error on central frequencies without a large degradation of the resolution. Moreover, three calibration algorithms were developed to achieve the expected resolution and correct mistakes on the amplitude and the phase with the new configuration (EFBD) Finally, the digital reconstruction system was implemented in 0.12 µm CMOS technology in order to evaluate their performances in term of area and maximum operating frequency.
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  • HAL Id : tel-00292340, version 2



Ali Beydoun. Systèmes de numérisation hautes performances à base de modulateurs sigma delta passe-bande. Traitement du signal et de l'image. Université Paris Sud - Paris XI, 2008. Français. ⟨tel-00292340v2⟩



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