Blaise Ravelo

Bio: Blaise Ravelo is an academic researcher from Nanjing University of Information Science and Technology. The author has contributed to research in topics: Group delay and phase delay & Microstrip. The author has an hindex of 21, co-authored 196 publications receiving 1727 citations. Previous affiliations of Blaise Ravelo include École Supérieure d'Ingénieurs en Génie Électrique & Nanjing University.

Study and Application of Microwave Active Circuits with Negative Group Delay

Abstract: A simple topology of an NGD active circuit consisting of a FET terminated by a shunt RLC-resonant network and dedicated to the microwave signals was proposed and extensively studied. To our knowledge, in this chapter, the first experimental time-domain demonstration of a circuit able to exhibit simultaneously gain and NGD in microwave domain is proposed. By injecting in the NGD circuit a sufficiently smoothed input short-pulse modulating a sine carrier, one gets an output having an envelop peak in advance compared with the input one. Of course, this phenomenon does not contradict the causality principle. It is also worth emphasizing that the tested circuit respects all required criteria of classical active microwave devices such as gain, matching and stability. As predicted in theory (Ravelo et al., 2007a, 2007b, 2007c and 2008a), for a prototype implemented in planar technology, we have measured in time-domain a pulse peak advance of about -2 ns or 24% of the 1/e-input pulse half-width without attenuation. It is also interesting to note that through this experimentation, the input noise contribution did not destroy the occurrence of time-domain advance induced by the NGD active circuit. Moreover, in this chapter, thanks to the S21-magnitude form, the understudied NGD circuit is able to exhibit a pulse compression phenomenon with a possibility of amplification. Then, it should be worth using the presented NGD active topology to compensate for dispersion effects and especially to reduce the intersymbol interference in certain telecommunication channels. As a potential application of this NGD circuit, a new principle of frequency independent phase shifter is proposed. By cascading a classical transmission line with this NGD circuit, a constant phase value is obtained. The efficiency of this principle was demonstrated by measurement. Indeed, a constant phase value of 90°±5° was obtained within a 76% relative frequency band centred at about 1.5 GHz. The impacts of the PS parameter variations and sensitivity analysis are stated. The main benefits of this NGD active PS concerns its compactness and also the facility to generate very low group delay, and the broad band characteristics. Besides, a two-stage NGD PS was also designed; the simulation results showed a bandwidth enhancement of the constant phase up to 125%. Some fields of applications such as the design of broadband active balun for RF front end architectures are discussed. As ongoing research, design of reconfigurable devices dedicated to telecommunication applications is envisaged. Future investigations will be devoted to the design of NGD devices able to operate at higher frequencies through the use of distributed elements. In this optic, the implementation of MMIC devices based on distributed elements is envisaged.

Theory on negative time-delay looped system

Abstract: An innovative theory on the looped system generating negative time delay is presented. Both the direct and delayed feedback loop topologies of this system essentially consist of an independent-frequency gain and time-delay block. It is shown theoretically that for suitable parameters the system can generate a negative time delay by virtue of a negative group delay (NGD). Analytical expressions reveal that the system presents an unconditional low-pass NGD behaviour. The NGD properties as a function of the system parameters are derived. To demonstrate the feasibility of the developed NGD system concept, frequency- and time-domain analyses are performed with Matlab, resulting in a very good agreement between the simulations and theory. Furthermore, as illustrated by computational results, negative time-delay signal propagation (signal advance) is obtained. The proposed NGD system can potentially be useful for time-delay compensation in engineering systems.

Multilayer power delivery network modeling with modified Kron's method (MKM)

Abstract: An efficient and unconventional modelling approach is established for the investigation of power delivery network (PDN) constituted by a multilayer printed circuit board (PCB) structure. The proposed model is applied to the power integrity (PI) analysis through a PDN structure with power/ground planes, vias and decoupling capacitors. The modelling methodology is based on the tensorial analysis of network (TAN) by using the modified Kron's method (MKM). The model computational algorithm is implemented as a Python program. First, the frequency dependent input impedance of the proposed multilayer PDN computed from the MKM is compared with 3D electromagnetic full wave simulations from DC to 2-GHz. Then, the instantaneous and spectrum of the distributed powers through the PDN are compared by considering a switched unit step input feeding voltage. As expected, a good prediction of the input impedance and power distribution is obtained. The proposed MKM numerical computation is beneficial compared to the 3D full wave simulation in terms of processing time and memory.

Zonal Thermal Room Original Model With Kron’s Method

Abstract: An original thermal model of a single room structure is developed by using the tensorial network-based Kron’s method. The modelling principle is using the equivalent RC-network of wall, door and air constituting the house. For a better understanding, the temperature propagation was assumed only in a 1-D horizontal direction. The problem geometrization is defined in function of rectangular approximation meshing. After the determination of the equivalent thermal resistor and thermal capacitor, the innovative thermal circuit representing the room is elaborated. The methodology of the Kron’s formalism, implicitly described with the different action steps is introduced. The thermal room Kron’s method is implemented from the branch to mesh spaces before the expression of the problem metric. The thermal transfer functions (TTFs) at three cases of indoor points, situated near, middle and far of the door are established from the Kron’s problem metric. The feasibility of the room thermal Kron’s TTF model is validated with SPICE TTF simulations in both frequency and time domains. The thermal cut-off frequencies are verified with very good correlation between the established TTF model and simulation. An excellent prediction of transient responses with unit-step and arbitrary waveform temperature signals with a minimal and maximal amplitude of about 20°C and 40°C is proposed.

Radiated EMC immunity investigation of common recognition identification platform for medical applications

Abstract: An innovative e-healthcare platform named common recognition and identification platform (CRIP) was developed and tested as part of the CareStore project. CareStore and CRIP aims at delivering accurate and safe disease management by minimising human operator errors in hospitals and care facilities. To support this, the CRIP platform features fingerprint biometrics and near field communication (NFC) for user identification; and Bluetooth communication support for a range of telemedicine medical devices adhering to the IEEE 11073 standard. The aim of this study was to evaluate the electromagnetic compatibility (EMC) immunity of the CRIP platform in order to validate it for medical application use. The first prototype of CRIP was demonstrated to operate as expected by showing the user identification function feasibility, both via NFC and biometric, and by detection of Bluetooth devices via radio frequency (RF) scanning. The NFC module works in the 13.56 MHz band and the Bluetooth module work in the 2.4 GHz band, according to the IEEE 802.15.1 standard. The standard test qualification of the CRIP was performed based on the radiated EMC immunity with respect to the EN 61000-4-3 standard. The immunity tests were conducted under industrial EMC compliance with electric field aggression, with levels up to 10 V/m in both horizontal and vertical polarisations when the test antenna and the CRIP were placed at a distance of 3 m. It was found that the CRIP device complies with the European electromagnetic (EM) radiation immunity requirements.

Similarity and Dimensional Methods in Mechanics

Abstract: By L I Sedov London: Cleaver-Hume Press Ltd Pp xvi + 363 Price 105s This is really two separate books within the same pair of covers First of all Chapters 1-3, some 145 pages, are devoted to the discussion of similarity and dimensional, methods and their application to a variety of problems in mechanics and fluid mechanics

Lectures on Theoretical Physics

Abstract: Vorlesungen uber theoretische Physik Von Prof. Arnold Sommerfeld. Band 1: Mechanik. Vierte, neubearbeitete Auflage. Pp. xii + 276. 18 D. marks. Band 2: Mechanik der deformierbaren Medien. Pp. xv + 376 + 4 plates. 18 D. marks. Band 3: Elektrodynamik. Pp. xvi + 368. 18 D. marks. Band 6: Partielle Differentialgleichungen der Physik. Pp. xiii + 332. 18 D. marks. (Wiesbaden: Dieterich'sche Verlagsbuchhandlung, 1947–1949.)

Harvesting Water Drop Energy by a Sequential Contact-Electrification and Electrostatic-Induction Process

Abstract: A new prototype triboelectric nanogenerator with superhydrophobic and self-cleaning features is invented to harvest water drop energy based on a sequential contact electrification and electrostatic induction process. Because of the easy-fabrication, cost-effectiveness, and robust properties, the developed triboelectric nanogenerator expands the potential applications to harvesting energy from household wastewater and raindrops.