| dc.description |
High performance multi-cell delta-sigma modulators are a preferred choice in applications which require programmability. Multi-cell delta-sigma modulators with M unit cells provide 10log10(M) SQNR improvement for the same thermal noise and bias power due to the uncorrelated quantization noises of the M unit ADCs. This concept is used in this thesis to illustrate novel third-order and fourth-order noise shaping structures using split ADC of second order, and hence providing higher-order noise shaping with the same thermal noise and bias power as that of a conventional second-order structure. The additional SQNR improvement due to split ADC can be traded off with power. Switched capacitor implementations are also proposed to confirm that both third-order and fourth-order noise shaping structures require only two opamps by using self-enhancement technique in a second-order single stage. The novel third-order structure discussed in this thesis is compared to a conventional second-order, a single-stage third-order and a 2+1 MASH in terms of performance, stability and sensitivity to opamp non-idealities. Similar comparisons are done for the proposed fourth-order structure with a conventional second-order, a single-stage fourth-order and a 2+2 MASH ADC. Simulation results show that the novel noise shaping structures for third and fourth order are highly robust, and show performance similar to other existing structures for the same order of noise shaping. |
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