Selim S. Awad

Determining ADC effective number of bits via histogram testing

A new application for one of the widely known A/D converter (ADC) dynamic testing methods, namely the histogram method, is discussed. After computing the transition voltages of the ADC transfer characteristics, the effective number of bits is computed. Simulation shows that this method more accurately characterizes the ADC used for arbitrary input signals, compared to the fast Fourier transform (FFT) and sine-fit methods which characterize the ADC in the light of an input sinusoid. The technique outperforms sinewave fitting as it gives more accurate results, while avoiding convergence problems of the iterative curve fitting algorithm. The FFT method was verified to be the least accurate. Simulation indications that the histogram method is better than the sine-fit method are presented. >

Analysis of accumulated timing jitter in the time domain

This paper deals with the effects of accumulated timing-jitter on the signal-to-noise ratio (SNR) of real sine waves. Such a problem was recently investigated by the author, using the discrete-Fourier method. However, the frequency-domain analysis has some limitations due to the fact that some of the accumulated timing-jitter noise power, found at the fundamental frequency component, would be added to the power of the input signal itself. Thus, in this paper, the analysis is performed in the time-domain and is restricted to the SNR measurement. An expression for the SNR in terms of timing-jitter distribution parameters, and the number of samples of the input signal, is developed. Computer simulations are presented, which showed excellent agreement with the developed expression. Also, a comparison between the results obtained from the time-domain analysis and the frequency-domain, is presented.

Advanced Driver Assistance Systems - Past, present and future

Every year, automobile manufactures spend millions in funding development of cutting edge technologies to keep drivers safe and accident free while operating their vehicles. These technologies are known in the industry as Advanced Driver Assistance Systems and each one is controlled by complex real-time embedded systems. This paper will present the state of the art for Advanced Driver Assistance Systems and will give detailed overviews of past, present and future designs of each variant. Each overview will focus on the design of the actual real-time embedded system involved.

Capacitance measurement based on an operational amplifier circuit: error determination and reduction

Errors introduced in an operational-amplifier-based sine-wave oscillator applied in capacitance measurement are considered. The errors due to the nonideal characteristics of the operational amplifier are addressed. The oscillator circuit was simulated using the SPICE program, and gives the opportunity to study the behavior of the circuit under nonideal conditions, and to estimate the errors introduced in the measured capacitance and the frequency of oscillation. It is shown that major sources of error are the gain-bandwidth product and the output resistance of the operational amplifier. Compensation techniques to reduce errors related to the gain-bandwidth product are presented. Experimental results confirming the error reduction are included. >

Analysis, design, and implementation of an AC bridge for impedance measurements

The paper reviews the digital AC bridge. A more accurate and thorough analysis of the bridge is presented. Based on the analysis a simple adaptive algorithm is proposed in order to ensure fast conversion. In addition, a new design of the bridge, based on the TMS 320C25, is given. The system is implemented with the Dalanco Spry model 25 DSP board, on a software system designed whereby an IBM PC host computer provides control of the bridge. Experimental results are presented. >

More on jitter effects on sinewave measurements

The measurement of signal-to-noise ratio (SNR) based on uniform sampling is investigated and compared with the results of Y. Jenq (see ibid., vol.37, p.245-251, June 1988) based on non-uniform sampling. Simulation results are provided to confirm the theoretical work. The authors then investigate amplitude and phase measurements and present new formulae for its statistics, which are more accurate than in their previous work (see ibid., vol.39, p.86-89, Feb. 1990). The approach followed in this study is also suitable for investigating signal measurements in the presence of other noise forms, e.g. quantization. >

A simple method to estimate the ratio of the second pole to the gain-bandwidth product of matched operational amplifiers

A simple method is proposed for estimating the ratio of the second pole to the gain-bandwidth product of matched operational amplifiers (OAs). This ratio is an important parameter in deciding the stability of composite OA-based circuits. The theoretical analysis of the method is presented, and experimental results are given. >

Extending the frequency range of a Wien-bridge oscillator using composite operational amplifiers

The author describes the use of composite operational amplifiers to extend the useful operating frequency range of an operational amplifier-based Wien-bridge oscillator. The effect of the finite gain-bandwidth product (GB) of the operational amplifier (OA) is analyzed. This analysis shows that for a certain GB the frequency of oscillation is less than the theoretical value and that the error increases with frequency. A composite OA is then used to decrease the errors due to GB. This is verified theoretically and experimentally. Although the composite OA improves the frequency performance of the oscillator, the amplitude of the output decreases with frequency. An automatic-gain control circuit is incorporated to keep an output amplitude constant over the useful frequency range. Distortion measurements are presented. >

An undergraduate digital signal processing lab as an example of integrated teaching

This paper describes the development of the undergraduate digital signal processing curriculum at the University of Michigan-Dearborn, Electrical and Computer Engineering Department. A real-time digital signal processing laboratory is setup to enhance digital signal, processing courses and to conduct senior capstone design projects. This effort has been supported by an NSF grant and by the University of Michigan-Dearborn.

The Electromagnetic Environment of an Automobile Electronic System

The objective of this paper is to report measured results of electric fields investigated inside the automobile. This investigation is important to the electronic design engineer before he starts the design of the different electronic systems needed to operate the automobile. By knowing the electromagnetic environment inside the automobile, the electronic engineer is given the opportunity to estimate and predict the various effects of electromagnetic disturbances on the automotive electronic systems. In our experiments, the work performed to study the electromagnetic environmental conditions was carried out on a typical midsize automobile with a high-power frequency-modulation (FM) transmitter installed inside the vehicle. Different antenna locations were used to radiate the electromagnetic waves that were studied. Data obtained from the experimental results are presented and discussed.