39 research outputs found
Multi-stage noise shaping (MASH) delta-sigma modulators for wideband and multi-standard applications
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Multibit delta sigma modulator with noise shaping dynamic element matching
Ph.DDOCTOR OF PHILOSOPH
Rapid Prototyping of Third-Order Sigma-Delta A/D Converters
Prototyping of third-order sigma-delta analog to digital converters (Æ©ÎADCs) has been presented in the paper. The method is based on implementation of field programmable analog arrays (FPAA) to configure and reconfigure proposed circuits. Three third-order Æ©Î ADC structures have been considered. The circuit characteristics have been measured and then the structure of the converters have been reconfigured to satisfy input specifications
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Analysis and design of bandpass delta-sigma A/D converters
A new approach to oversampled delta-sigma A/D converters ( AZ modulators ) is introduced, where a differential pseudo-Npath filter stage is used as a basic cell. In this band-pass application, the z to -zN transformation is employed to realize a
RAM-type pseudo-2-path lossless integrator. The bandpass second-order and 4th-order delta-sigma A/D converters are implemented by
switched-capacitor ( SC ) circuits using this kind of integrator. The effects of components inaccuracy, finite op-amp gain, as well as
clock feed-through noise are studied in simulations. The results verify that such A/D converters possess a remarkable insensitivity
to imperfect components and a high signal-to-noise ratio (SNR). A 6th-order dual-quantizer delta-sigma A/D converter with a digital canceller is then designed, which achieves 86 dB (>14 bit) conversion accuracy and 95 dB (>15 bit) dynamic range for a low
oversampling ratio (OSR=32) even with low-accuracy analog components (4-bit internal D/A with 6-bit linearity)
Contribution to the design of continuous -time Sigma - Delta Modulators based on time delay elements
The research carried out in this thesis is focused in the development of a new class of data converters for digital radio. There are two main architectures for communication receivers which perform a digital demodulation. One of them is based on analog demodulation to the base band and digitization of the I/Q components. Another option is to digitize the band pass signal at the output of the IF stage using a bandpass Sigma-Delta modulator. Bandpass Sigma- Delta modulators can be implemented with discrete-time circuits, using switched capacitors or continuous-time circuits. The main innovation introduced in this work is the use of passive transmission lines in the loop filter of a bandpass continuous-time Sigma-Delta modulator instead of the conventional solution with gm-C or LC resonators. As long as transmission lines are used as replacement of a LC resonator in RF technology, it seems compelling that transmission lines could improve bandpass continuous-time Sigma-Delta modulators. The analysis of a Sigma- Delta modulator using distributed resonators has led to a completely new family of Sigma- Delta modulators which possess properties inherited both from continuous-time and discretetime Sigma-Delta modulators. In this thesis we present the basic theory and the practical design trade-offs of this new family of Sigma-Delta modulators. Three demonstration chips have been implemented to validate the theoretical developments. The first two are a proof of concept of the application of transmission lines to build lowpass and bandpass modulators. The third chip summarizes all the contributions of the thesis. It consists of a transmission line Sigma-Delta modulator which combines subsampling techniques, a mismatch insensitive circuitry and a quadrature architecture to implement the IF to digital stage of a receiver