A non-invasive method for detecting the Heart Rate (HR) and the variation in the HR that aids in providing continuous, safe and effective monitoring of drowsiness of an automotive driver or a power tool operator is presented in this paper. HR is detected using an appropriately located photoplethysmograph (PPG) sensor. A simple but reliable detection scheme is developed to accurately measure HR from the PPG signal. The scheme produces a quasi-digital signal, enabling easy interface to a digital system. This signal is independent of base-line and peak-to-peak variations that are present in consecutive cycles of a PPG signal. A prototype sensor and detection circuit has been built and tested. A suitable virtual instrument has been developed, which acquires and process the signals from the detection unit to obtain the HR and its variability. Tests have been conducted on volunteers to observe HR variation between awake and drowsy conditions. A consistent trend of reduction in HR was observed as the subject changes the state from awake to sleep, which may be used as one of the parameters to monitor drowsiness. Tests were also performed, using suitably developed sensors, to check the reliability of the scheme while driving a vehicle. It recorded the HR data accurately while driving.

This paper presents the design, modelling and analysis of novel multi-path time-interleaved analog and digital sigma-delta modulators that can operate at any arbitrary centre-frequency from DC to Nyquist. Dual- and quadruple-path fourth-order Butterworth, Chebyshev, inverse Chebyshev and elliptical based sigma-delta modulators are designed, which offer designers the flexibility of specifying the centre-frequency, pass-band/stop-band attenuation as well as the signal bandwidth. These topologies are compared in terms of their signal-to-noise ratios, hardware complexity, stability, tonality and sensitivity to non-idealities. In addition, this paper presents the mathematical modelling and evaluation of tones caused by the finite wordlengths of these digital multi-path sigma-delta modulators when excited by sinusoidal input signals.

Fault-tolerant converters have been widely investigated for years and nowadays an extensive technical literature on this field exists. This paper presents a novel fault detection algorithm based on a simple geometrical approach. In the algorithm analysis both the case of faults in single device and the loss of an entire inverter leg have been considered. The proposed methodology is characterized by simplicity, low computational and implementation effort with a consequent fast execution and easy control integration. The suggested algorithm is verified by means of experimental tests and reveals a valid and suitable alternative to the existing state of the art in the field of inverter fault detection.

This paper presents the study of a novel parallel architecture of analog-to-digital converters (ADCs) based on sigma delta (ΣΔ) modulators using frequency band decomposition (FBD). This architecture is intended for wideband applications with a fractional bandwidth equal to 40% and composed of four channels of 6^th order band-pass discrete time (DT) ΣΔ modulators with single-bit quantization. The simulation results prove that this architecture is able to provide a signal-to-noise ratio (SNR) over 50 dB. These results satisfy the wideband standard requirements. However, parallel architectures are sensitive to channel mismatches. In this paper, we are interested in studying the robustness of our FBD architecture to clock skew mismatch errors. It is shown that the clock skew causes the SNR to decrease by at most 6 dB.

This paper describes a freely available, open source, user-friendly data evaluation program developed for ADC testing with a sine wave. This tool performs multiple kinds of mathematical methods (nonlinear least squares and maximum likelihood) to extract the information from the recorded data. It has been created in the form of a Matlab toolbox for users who have some knowledge in ADC testing, and would like to perform the mathematical computations in an efficient way – especially those that require complex numerical methods Error! Reference source not found.. As it is equipped with a graphical user interface, its usage does not require any programming knowledge, nevertheless one can even get familiar with the framework of the software, as the program files contain the source code that runs using the Matlab interpreter. A further important goal of this software is to create the possibility of publishing reproducible ADC test evaluation results. Statements of related papers can be verified easily: if the raw data are shared, the computations can be repeatedly executed using this software tool.