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Efficient level crossing sampling for high-fidelity, alias-free analogue-to-digital conversion
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Riazifar, Negar (2022) Efficient level crossing sampling for high-fidelity, alias-free analogue-to-digital conversion. PhD thesis, University of Warwick.
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Official URL: http://webcat.warwick.ac.uk/record=b3815658
Abstract
This thesis proposes strategies in level crossing (LC) sampling and reconstruction that provide high fidelity signal reconstruction for speech signals; these strategies circumvent the problem of exponentially increasing number of samples as the bit-depth is increased and hence are highly efficient. Specifically, the results indicate that the distribution of the intervals between samples is one of the key factors in the quality of signal reconstruction; including samples with short intervals do not improve the accuracy of the signal reconstruction, whilst samples with large intervals lead to numerical instability.
The proposed sampling method, termed reduced level crossing (RLC) sampling, exploits redundancy between samples to improve the efficiency of the sampling without compromising performance. The RLC sampling improves the efficiency of the sampling by excluding samples that occur within a specified interval of the previous sample.
A reconstruction technique is also proposed that enhances the numerical stability through linear interpolation of samples separated by large intervals. Interpolation is demonstrated to improve the accuracy of the signal reconstruction in addition to the numerical stability. It is further demonstrated that the RLC and interpolation methods can give useful levels of signal recovery even if the average sampling rate is less than the Nyquist rate.
The results also indicate that the distribution of the intervals between samples highly affects aliasing; introducing randomness into the time intervals between samples leads to alias-free behaviour. The alias-free property enables a significant reduction in the number of samples whilst maintaining functionally useful signal quality. Moreover, the hardware of the electronics can be simplified because expensive anti-aliasing filters are not required.
The proposed methods could have a potential advantage for reducing data storage or transmission requirements as well as reducing the power of down-stream processing and computational complexity. The criteria for reducing sample density and interpolation would be relatively straightforward to implement in hardware and hence these techniques could lead to practical methodologies.
Item Type: | Thesis (PhD) | ||||
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Subjects: | T Technology > TK Electrical engineering. Electronics Nuclear engineering | ||||
Library of Congress Subject Headings (LCSH): | Speech processing systems, Signal processing -- Digital techniques, Analog-to-digital converters | ||||
Official Date: | January 2022 | ||||
Dates: |
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Institution: | University of Warwick | ||||
Theses Department: | School of Engineering | ||||
Thesis Type: | PhD | ||||
Publication Status: | Unpublished | ||||
Supervisor(s)/Advisor: | Stocks, Nigel G. | ||||
Format of File: | |||||
Extent: | xvii, 175 leaves : illustrations | ||||
Language: | eng |
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