Louiza Sellami

Linear bilateral CMOS resistor for neural-type circuits

A previous CMOS bilateral linear resistor is analyzed and shown to be reducible from four to two transistors with improved linearity. This is developed for neural-type circuits to allow its use in emulating both excitatory and inhibitory voltage variable synapses. Simulation results using parameters of MOSIS transistors are presented to verify the theory.

A digital scattering model of the cochlea

A cascade digital scattering linear model of the cochlea, suitable for Kemp echo cochlea characterization, is developed. This model stems from a unidimensional transmission line model in which nonuniform and loss properties are included. Its lattice structure is obtained by rephrasing the model equations in terms of incident and reflected scattering waves. A characterization of the cochlea, through the estimation of the width, the stiffness, and the damping of the basilar membrane, is made with the model and the results compared to data available in the literature.

Synthesis of ARMA filters by real lossless digital lattices

A new method is presented to obtain degree-one or real degree-two transfer scattering matrices of two-port lossless lattice filters through the use of complex Richards function extractions for the minimum degree cascade synthesis of real, stable, single-input, single-output ARMA (n, m) filters from the transfer function or the input reflection coefficient. The method relies on a four-step Richards function extraction where two steps are used for reducing the degree of the transfer function and two for obtaining real lattices. We treat the cases where the zeros of transmission are inside and outside the unit circle but not on the unit circle.

A CMOS PWL fuzzy membership function

The membership function, classically constructed from piecewise linear (PWL) functions, is one of the most important components in fuzzy neural systems. Here we give an improved current mode CMOS circuit suitable for design of fuzzy membership PWL functions. The circuit with bi-directional input is based upon an improved current mirror and is suitable for VLSI fabrication via the MOSIS CMOS process.

Current mode realization of ear-type multisensors

We present a MEMS, switched current mode circuit that realizes a multi-ear type system. A novel sensor, acts as a pressure transduction mechanism for input to cochlear-type processing. Z-transform computation of fluid motion in the tubules of the cochlea is realized with a switched current lattice cascade. We also describe how an array of MEMS-SI circuits can be placed for use as a multisensor, intended for sound-beam forming, accomplished with n-aural hearing.

Speech coding and phoneme classification using MATLAB and NeuralWorks

Applications involving speech coding and phonetic classification are introduced as educational tools for reinforcing signal processing concepts learned in senior level communication classes at the US Naval Academy. These applications utilize the software packages MATLAB and NeuralWorks and are used to explore the concepts of impulse sampling, Fourier transforms, data windowing, and homomorphic filtering.

A MOSFET bridge fluid biosensor

This paper presents a MOSFET based biosensor circuit for the monitoring of such things as creatinine in patients with renal failure. Its VLSI layout is presented for 1.2 /spl mu/ or for 2.0 /spl mu/ MOSIS CMOS processes. The proposed biosensor circuit is a capacitive gap sensor where the device consists of a bridge made of three standard PMOS devices connected either as resistors or capacitors and forming three arms of the bridge. The fourth arm is a similar PMOS transistor but with a gap between the channel and a raised poly layer in which a fluid, such as creatinine, or a gas, can be placed. PSpice simulations and Spice extractions from the layout are included to demonstrate the operation of the circuit.

A switched current mode real ear-type lattice

Switched current circuits are used here to design real degree-one discrete time lattices for use in modeling the inner ear portion of ear-type networks. This lattice is characterized as an electrical two port system and is, therefore, described by a transfer scattering matrix relating input and output signals. This matrix is degree-one and requires only one delay function, which we realize with a switched current circuit containing only one delay. This circuit uses a new sampling switch that substantially reduces the distortion occurring due to the clock feed through in conventional MOS based switches. Spice simulation results are included to support the theory.

Lossy synthesis of digital lattice filters

A new method fur converting a lossless cascade lattice realization of a real, stable, single-input, single-output (ARMAn, n) filter, with a lossy constant terminating one-port section, to a lossy realization is proposed. The conversion process is carried out through the factorization of the transfer scattering matrix of a two-port equivalent of the terminating section and the distribution of the loss term, embedded in this matrix, among the lossless lattice sections according to some desirable pattern. The cascade is then made computable through the extraction of right-matched I-unitary normalization sections. The technique applies to both degree-one and degree-two lattice sections, and is rendered systematic owing to the particular lossless lattice structure used. The motivation for this work lies in the synthesis of a pipeline of digital cochlea lattices with loss suitable for hearing impairment diagnosis via Kemp echoes.

Computable real lattice structures for cochlea-like digital filters

A synthesis algorithm for a pipelined lattice implementation of cochlea-like digital filters is presented, based upon the properties of real, lossless lattice synthesis of ARMA filters. The algorithm operates on a simplified characterization of elementary lattice sections of degree one or degree two. This leads to a structure that is recursively designed and for which each lattice is precisely implemented by a pair of complex conjugate transmission zeros via Richards function extractions. Except for zeros of transmission on the unit circle, all other types and multiplicities are allowed. Necessary and sufficient conditions are derived for the degree-two lattices to guarantee computability, i.e., realizability with no delay-free loops. In addition to being suitable for VLSI realization, the structure enables a systematic cochlea assessment from the scattering ear parameters.