Mustapha Hamad

An RFID attendance and monitoring system for university applications

The main objective of this paper is to enhance the universitys monitoring system taking into account factors such as reliability, time saving, and easy control. The proposed system consists of a mobile RFID solution in a logical context. The system prototype and its small scale application was a complete success. However, the more practical phase will not be immediately ready because a large setup is required and a part of the existing system has to be completely disabled. Some software modifications in the RFID system can be easily done in order for the system to be ready for a new application. In this paper, advantages and disadvantages of the proposed RFID system will be presented.

An Educational Board for Teaching Microcontroller System Design Laboratory

Teaching undergraduate electrical and computer engineering students microcontroller/microprocessor design concepts is essential in today’s highly advanced technological environment. Furthermore, we believe that all engineering students should take an introductory course in this area. With this objective in mind, we have developed an educational board to teach microcontroller circuit design laboratory. The development board is based on PIC16F877A microcontroller from Microchip. In addition, essential software routines, and a laboratory manual that contains a list of design-applications experiments are part of this lab.

FPGA implementation of a three-way asynchronous DDR2 memory controller

This paper describes the implementation of a three-way asynchronous Double Data Rate (DDR2) memory controller using a Field-Programmable Gate Array (FPGA). The objective is to replace the memory buffer in a PC-based oscilloscope, where a First-In First-Out (FIFO) stack was used. The digital oscilloscope is used for measuring and reconstructing eye diagrams for high speed signals, such as Ethernet (1.25, 10.3125 Gbps), PCI-Express (2.5, 5.0, 6.125 Gbps), SATA (1.5, 3.0 Gbps), etc... Replacing the stack with DDR2, improves the quality of the eye diagram, which describes parameters of the input signal, for the DDR2 higher data transfer speed and larger memory size.

A PIC-Based Microcontroller Design Laboratory

Teaching undergraduate electrical and computer engineering students microcontroller/microprocessor design concepts is essential in todays highly advanced technological environment. Furthermore, the authors believe that all engineering students should take an introductory course in this area. With this objective in mind, a PIC-based microcontroller design laboratory was developed. This Laboratory consists of a development board based on PIC16F877A microcontroller from microchip, essential software routines, and a laboratory manual that contains a list of design-applications experiments

Equivalent circuit modeling of the dynamic operation of ultra-high speed multi-mode VCSELs

Vertical-cavity surface-emitting lasers (VCSELs) have emerged as a pioneering solution for many high-speed data communication challenges. Compared to large-signal analyses, the small-signal modulation response of a VCSEL can be isolated from the entire system, thus providing accurate information on the intrinsic laser dynamics. An alternative approach to that of using the rate equations is to transform theses rate equations to an equivalent circuit model. The dynamic operation characteristics including the device-circuit interaction can then be modeled and optimized using a circuit simulation software. Until now, it was assumed that the dynamic behavior of oxide-confined multi-mode VCSELs can be modeled using the single-mode rate equations developed for edge-emitters, even though the deviation between the single-mode based model and the measured data is substantially large. Furthermore, equivalent electrical circuit modeling of the VCSELs’ intrinsic dynamics was only done by modeling derived from the single-mode rate equations. Therefore, a new electrical circuit model, that can accurately describe the dynamic behavior of these VCSELs, is needed. In this work, electrical circuit modeling of the dynamic performance of multi-mode VCSELs, for the case where lasing modes do not share a common carrier reservoir, is presented. The electrical circuit model is derived from innovative advanced multi-mode rate equations that take into account the effect of spatial hole burning, gain compression, and inhomogeneity in the carrier distribution. The validity of the model is affirmed through experimental data fittings and plots of their modulation response are presented.

De-embedding device parasitics of ultra-high speed VCSELs

To establish highly performing vertical cavity surface-emitting lasers (VCSELs), it is essential to have an adequate understanding of the intrinsic laser dynamics of these devices. However, this is done while bearing in mind that extrinsic parasitic elements in VCSELs play an important role in limiting the intrinsic modulation bandwidth. In this work, we analyse different electrical parasitic equivalent circuit models in the aim of comparing them and selecting the one that can best describe and represent the physical properties of our high-performance VCSELs. Through measuring the microwave reflection coefficient S11(f), then fitting it with the calculated one from the equivalent circuit impedance model, the parasitic components of the equivalent circuit model can be extracted. The S11(f) data was collected over different ranges of operating bias currents and using a 7 μm oxide aperture diameter VCSEL. This allows us to observe the variations of these circuit elements with respect to the current and compute the transfer function and the resulting parasitic cut-off frequencies (bandwidth limitation) for each model. After plotting and comparing the transfer functions of the different models together, under the same driving current, it was found that the discrepancy between the two curves, in a specific frequency range, is rather small over the VCSEL bandwidth of interest, hence allowing us to use the first-order low pass filter to de-embed the parasitic contributions and separate them from the device intrinsic response. However, over higher frequency ranges, the deviation is found to be substantial and the extract parasitic transfer function should be taken into consideration. Another issue to be addressed is the reliability of the simple circuit models to extract accurate circuit component values, especially when the deviation between the measured microwave reflection coefficient S11(f) and the fitted model is substantially large. This discrepancy is due to the oversimplification imposed on the equivalent circuit model, leading to a high level of uncertainty in the extracted circuit component values. Thus, sufficient modelling and accurate fitting strategies are needed for a reliable parasitic de-embedding approach.

Small-signal analysis of ultra-high-speed 30 GHz VCSELs using an advanced multi-mode approach

Vertical-cavity surface-emitting lasers (VCSELs) have emerged as a pioneering solution for many high-speed data communication challenges. Therefore, higher bandwidth optical interconnects with data rates in the range of 100 Gbit/s require directly modulated VCSELs with ultimate speed ratings. The small-signal modulation response of a VCSEL can be isolated from the entire system, thus providing accurate information on the intrinsic laser dynamics. Until now, it is assumed that the dynamic behavior of oxide-confined multi-mode VCSELs can be fully modeled using the single-mode rate equations developed for edge-emitters, even though the deviation between the single-mode based model and the measured data is substantially large. Using an advanced theoretical approach, rate equations for multi-mode VCSELs were developed and the small-signal modulation response of ultra-high speed devices with split carrier reservoirs corresponding with the resonating modes were analyzed. Based on this theoretical work, and including gain compression in the model, the analyzed VCSELs showed modulation bandwidth around and exceeding 30 GHz. The common set of figures of merit is extended consistently to explain dynamic properties caused by the coupling of the different reservoirs. Furthermore, beside damping and relaxation oscillation frequency, the advanced model, with gain compression included, can reveal information on the photon lifetime and highlights high-speed effects such as reduced damping in VCSELs due to a negative gain compression factor.

A smart device for the detection of heart abnormality using R-R interval

Heart disease is the number one cause of death for both men and women worldwide. Heart attacks represent 30% of global fatalities and are classified as high medical emergencies. Unfortunately, almost half of mortal sudden cardiac arrest occurs outside a hospital. In an attempt to decrease this rate and thus, be able to save lives, it is decisive to anticipate a heart attack by early detection of concomitant signs. Furthermore, if associated symptoms of heart abnormalities such as arrhythmias could be foreseen, unaware patients could be alerted beforehand thus, granting them precious time to seek effective medical assistance. Finally, patients with heart conditions are at high risk of running irreversible incidents when left alone at home without close surveillance or monitoring. The objective of this paper is to present a comprehensive platform with a threefold objective aiming at contributing towards a vital solution to the aforementioned unfortunate encounters. The platform consists of an electronic device interfaced with a smart phone that will acquire electrocardiogram (ECG) signals around the clock, and using inter-beat (R-R) interval analysis, alert the patient at once, and instantly contact a preprogrammed emergency service number when a risk threshold is gauged.

Semiconductor optical amplifier-based all-optical modified signed-digit adder

In this paper, we present an all-optical implementation high-speed arithmetic using the carry-free property of the modified signed-digit (MSD) number representation. The implementation is based on semiconductor optical amplifier (SOA) and Mach-Zehnder interferometer (MZI) switches, which represent the most promising solution due to their compact size, thermal stability and low power operation. The all-optical implementation uses two-valued logic encoding: (a) ¿sign¿ and ¿value¿ encoding <s,v> and (b) negative¿ and ¿positive¿ flags encoding <n,p> whereby the MSD digits -1, 0, and 1 digits are represented by {(1,1), (0,0), (0,1)} and {(1,0), (0,0), (0,1)}, respectively.

TOWARD A MINIATURIZED GENERATION OF ULTRASONIC-BASED DEVICES

This paper concerns the design method and implementation of main modules, dedicated to miniaturized digital ultrasonic devices, using advanced System-on-Chip technique. It is intended to diagnostic imaging applications such as echography. The proposed implementation allows the integration of all acquisition front end as well as signal and video processing on only one single chip. It will make possible to visualize the ultrasound images in real time. It requires high resolution and real-time image processing. The proposed design, which integrates the B-mode processing modules, includes digital beamforming, quadrature demodulation of RF signals, digital filtering, envelope detection, and video processing of the received signals. This system handles 128 scan lines and 6400 samples per scan line with a 90° angle of view span. The design uses a minimum size look-up memory to store the initial scan information. Rapid prototyping based on ARM/FPGA platform combination is used to validate the operation of the described system. This system offers significant advantages of portability and a rapid time to market.