Mehdi Terosiet

FPGA implementation of reconfigurable ADPLL network for distributed clock generation

This paper presents an FPGA platform for the design and study of network of coupled All-Digital Phase Locked Loops (ADPLLs), destined for clock generation in large synchronous System on Chip (SoC). An implementation of a programmable and reconfigurable 4×4 ADPLL network is described. The paper emphasizes the difference between the FPGA and ASIC-based implementation of such a system, in particular, implementation of digitally controlled oscillators and phase-frequency detector. The FPGA-implemented network allows studying complex phenomena related to coupled ADPLL operation and exploiting stability issues and nonlinear behavior. A dynamic setup mechanism has been proposed for the network, allowing selecting the desirable synchronized state. Experimental results demonstrate the global synchronization of network and performance of the network for different configurations.

A self-sufficient digitally controlled ring oscillator compensated for supply voltage variation

A self-sufficient Giga-Hertz digitally controlled ring oscillator for clock distribution network is presented in this paper. It features a high supply insensitivity in order to mitigate the additional jitter due to supply noise. This is achieved by inducing a mutual compensation between the oscillation frequency parameters that are affected by the supply voltage variations. The proposed method can be easily implemented and takes advantage of the deep sub-micrometer effects peculiar to topical CMOS technologies. We demonstrate by simulations that this approach remains efficient over process variations despite the reliability issue of short channel MOS transistors.

Prototype of a multispectral and multiwavelength pulse oximeter based on a BQJ sensor

Pulse oximetry is one of the most commonly employed monitoring modalities in critical care setting. Conventional pulse oximeters, use two leds and a photodiode to estimate the percentage of oxyhemoglobin and deoxyhemoglobin, assuming that those are the only light absorbers in the blood. Nevertheless, the presence of other types of dyshemoglobin may invalidate their calibration. In this study, we employed a Buried Quad Junction photodetector in order to estimate the oxygen saturation using simultaneously lit leds. More precisely, a proof-of-principle was shown for developing an oximeter capable of estimating up to four types of hemoglobin simultaneously with a single led. Results from in vivo measurements obtained with this setup show that we successfully isolated the information of our interest for oxygen saturation estimation. These results were compared with a commercial device yielding acceptable estimations with a mean error of 1.3% of the oxygen saturation estimation.

Hardware Platforms Benchmark For Real-Time Polyp Detection

In this article, our concern is the early diagnosis of colorectal cancer from a computeraided detection point of view in order to help physicians in their diagnosis during the gold standard examination: optical video colonoscopy. Since many years, some methods and materials have been developed to reduce the polyp miss rate and to improve detection capabilities. Nevertheless, the real challenge lies in the real-time use of these methods. In this context, more precisely, we focus our attention on the hardware implementation of a previous method we recently introduced in the literature for real-time detection of colorectal polyps, lesions that may degenerate into cancer. This implementation is subject to three performance criteria: real-time processing capabilities, detection rate and necessary computational resources. Six different platforms were tested and compared. If we noticed that only workstation computers are able to perform the detection with a good tradeoff between the three aforementioned criteria, possibilities of architecture optimizations are also identified and discussed in order to achieve real-time performance on platforms with low available computational resources like Raspberry Pi for instance. This latter issue is of major importance for possible integration of the detection algorithm inside smallconnected object like videocapsule, a promising alternative to standard colonoscopy.

Wireless and Portable System for the Study of in-vitro Cell Culture Impedance Spectrum by Electrical Impedance Spectroscopy

A wireless and portable system, consisting in an electronic board and a computer software graphical interface, is presented in this article as a feasible way to do in-vitro electric bioimpedance spectroscopy of cells. It is designed to work inside a culture chamber performing impedance measurement in the frequency range of 64Hz to 200KHz. The board is equipped with a Bluetooth Low Energy (BLE) module allowing it to be wirelessly controlled. The software interface (also called ISMI) is coded with all required functionalities to manage the parameters of the board such as start frequency and sweep, measuring intervals, data acquisition and visualization and also a function to perform automatic measuring between desired time intervals during whole day for many days. In addition, the electrodes used for the measurements of cells are characterized giving an impedance magnitude between 103 to 105 ohms in a frequency range of 300Hz to 100KHz and a maximum voltage without considerable electrode deterioration of 120mVpeak. This information is used in the calibration of the ISMI system giving a measurement accuracy above 98% when compared with simulation results and with a reference instrument. The proposed system is an introductory step in the study of cells related to fibrous tissue induced by implants showing to be a viable and reproducibility-improving approach for such analysis. This first prototype provides information regarding the requirements for the design of an integrated version for embedded applications.

Improvement of a FPGA-based Detection of QRS Complexes in ECG Signal using an Adaptive Windowing Strategy

This paper presents an FPGA-based algorithm for automatic detection of QRS complexes in ECG signals, first step for the estimation of cardiac intervals. The proposed algorithm is divided into 3 parts : Filtering, Contrast Enhancement, and finally a Detection block based on an adaptive windowing and a thresholding of the enhanced data. The entire detection scheme was developed in accordance with embedding constraints and in the perspective of a real-time use. We evaluated the algorithm on manually annotated databases, such MIT-BIH Arrythmia and QT databases. The FPGA-based algorithm correctly detects 91,85 % percent of the QRS complexes, with a very limited ratio of false detection (only 5%) on standard databases, while for realtime records obtained from young subjects between 20 and 25 years, the sensitivity reaches 93,77 % with a false detection ratio of only 4 %. These results are in accordance with the most recent state-of-the-art off-line algorithms on the same database, and improves significantly FPGA-based ones that were tested on a limited number of ECG extracted from the MIT-BIH set of data only.

In vivo NIRS monitoring in pig Spinal Cord tissues

Little is known about the processes occurring after Spinal Cord damage. Whether permanent or recoverable, those processes have not been precisely characterized because their mechanism is complex and information on the functioning of this organ are partial. This study demonstrates the feasibility of Spinal Cord activity monitoring using Near Infra-Red Spectroscopy in a pig animal model. This animal has been chosen because of its comparable size and its similarities with humans. In the first step, optical characterization of the Spinal Cord tissues was performed in different conditions using a spectrophotometer. Optical Density was evaluated between 3.5 and 6.5 in the [500; 950] nm range. Secondly, adapted light sources with custom probes were used to observe autonomic functions in the spine. Results on the measured haemodynamics at rest and under stimulation show in real time the impact of a global stimulus on a local section of the Spinal Cord. The photoplethysmogram signal of the Spinal Cord showed low AC-to-DC ratio (below to 1 %).

An analytical model of the oscillation period for tri-state inverter based DCO

Tri-state inverter based DCO are emerging as an attractive circuit for the implementation of fully digital PLL. In this paper, we first introduce an analytical expression of the tuned period as a function of design and technology parameters. Then, we propose a sizing methodology for the CMOS implementation of a tri-state inverter based DCO. Finally, we applied this methodology to the design of such a DCO. We achieved an average error of 5.4% for our analytical expression compared to simulation results. In conclusion, we showed that our analytical expression and sizing methodology are directly applicable to the design of tri-state inverter based DCO.