Oversampled delta-sigma modulation is one of the widely used A/D conversion
techniques for narrow bandwidth signals. In this study several new lowpass and
bandpass delta-sigma modulator architectures as well as novel pseudo-N-path integrators
that can be used in implementing these architectures are proposed.
By using multiplexing techniques the new lowpass delta-sigma modulator
architectures exchange higher clock rates with hardware complexity. For a given
oversampling ratio (OSR), the multiplexed first-order delta-sigma modulator achieves a
higher resolution. Guaranteed stability is a very desirable feature of these structures.
The multi-loop delta-sigma modulator architecture similarly reduces the number of
integrators needed to achieve high-resolution conversion for a given OSR. To ensure
stability a quantizer with (N+1) bits must be used, where N is the number of loops, or in
other words, the order of the delta-sigma modulator. Digital correction or randomizing
techniques can be used to eliminate the performance reduction due to digital-to-analog-
(D/A) converter nonlinearity error [59], [64].
Bandpass delta-sigma modulators are useful for applications such as AM radio
receivers, spectrum analyzers, and digital wireless systems. Using z --> -z[superscript N] or z --> z[superscript N] mapping, a low pass delta-sigma modulator can be transformed to a bandpass one. One
of the methods to implement the loop filters in bandpass delta-sigma modulators is to use Pseudo-N-Path (PNP) switched-capacitor (SC) integrators. The advantage is that the center frequency occurs exactly at an integer division of the sampling frequency because of the number of physical paths. To achieve maximum resolution, integrators that do not suffer from clock feedthrough peaks are needed. The proposed differential and single-ended novel PNP integrators address this problem [76]. To keep the opamp specifications less stringent while achieving high resolution, these PNP integrators have been further improved with gain compensation techniques [53]. / Graduation date: 1997
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/34330 |
| Date | 14 March 1997 |
| Creators | Yesilyurt, Ayse Gul |
| Contributors | Ternes, Gabor C., Kenney, John G. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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