Institute for Systems Research Technical Reports

Permanent URI for this collectionhttp://hdl.handle.net/1903/4376

This archive contains a collection of reports generated by the faculty and students of the Institute for Systems Research (ISR), a permanent, interdisciplinary research unit in the A. James Clark School of Engineering at the University of Maryland. ISR-based projects are conducted through partnerships with industry and government, bringing together faculty and students from multiple academic departments and colleges across the university.

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Author: search.filters.author.Shamma, S.Subject: search.filters.subject.Communication

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    Classification of the Transient Signals via Auditory Representations
    (1991) Teolis, A.; Shamma, S.; ISR
    We use a model of processing in the human auditory system to develop robust representations of signals. These reduced representations are then presented to a neural network for training and classification.

    Empirical studies demonstrate that auditory representations compare favorably to direct frequency (magnitude spectrum) representations with respect to classification performance (i.e. probabilities of detection and false alarm). For this comparison the Receiver Operating Characteristic (ROC) curves are generated from signals derived from the standard transient data set (STDS) distributed by DARPA/ONR.

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    Cochlear Filters Design Using a Parallel Dilating-Biquad Switched-Capacitor Filter Bank
    (1991) Lin, Jyhfong; Ki, Wing-Hung; Thompson, K.E.; Shamma, S.; ISR
    A parallel filter bank is proposed to implement cochlear filters using very large time-constant (VLT) switched-capacitor (SC) filters. Significant hardware reduction is achieved in three ways. First, VLT SC biquads are used where the capacitor spread ratio of each biquad is about inversely proportional to the square root of wT, w is the center frequency of the filter and T is the inverse of the sampling frequency of the biquad. Second, the number of biquads is reduced by biquad sharing where n-biquad per channel cochlear filters are realized with only one additional biquad per channel after the first channel. Finally, LPN-type filter is used to avoid the very small capacitor in the forward path of each biquad. Furthermore, this filter bank s not only parasitics-insensitive but also gain-and-offset compensated using biphase clocking.
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    Realization of Cochlear Model by VLT Switched-Capacitor Filter Biquads
    (1991) Lin, Jyhfong; Ki, Wing-Hung; Thompson, K.E.; Shamma, S.; ISR
    We describe here the realization of a cochlear model using switched capacitor filters (SCF). This approach is made possible by a new design technique, called charge differencing (CD), which reduces by up to 50% the silicon area required to implement very large time-constant (VLT) filter biquads. In this technique, filter time constants are controlled by ratios of capacitor differences making the capacitor spread ratio very small. The new SCF's are also parasitics-free and are stabilized against op-amp inaccuracies, such as input offsets and finite gains, using a two-phase gain-offset-compensation method.