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.

Calculation of the time domain z-component of the EM-near-field from the x- and y-components

Abstract: This paper presents a time-frequency computation method for extracting the vertical component of magnetic near-field H z (t) from the horizontal components H x, y (t) by using the Plane Wave Spectrum (PWS) method. As PWS applies to frequency-domain quantities, a Fourier transform is used to convert between time- and frequency-domain fields. The method is validated on the example derived from the time-domain EMC radiated emission modeling, in which a set of electric dipoles is excited by current pulses of ultra-short duration. A good agreement has been found between magnetic near-field H z (t) extracted by the proposed method and that directly calculated from analytical formulae.

Negative Group Delay Theory of a Four-Port RC-Network Feedback Operational Amplifier

Abstract: An innovative negative group delay (NGD) theory based on a unity direct chain feedback (UDCF) circuit topology is developed in this paper. This NGD circuit is an active cell constituted by an operational amplifier in feedback with a four-port RC-network. This NGD circuit theory is developed based on the S-parameter model analytically established from the equivalent impedance matrix. The UDCF group delay frequency response is expressed as a function of the feedback RC-cell and the operational amplifier parameters. The NGD analysis of the developed UDCF cell is introduced. According to theoretical analysis, under a certain condition, the UDCF topology is susceptible to behave as a low-pass NGD function. The UDCF cell NGD characteristics are defined theoretically. The theoretical prediction is verified numerically and experimentally in both the frequency- and time-domain by designing and fabricating an active PCB prototype. The simulations and experimentations show that the UDCF circuit exhibits an NGD of approximately -38 ns with NGD cut-off frequency of about 5.5 MHz. More importantly, it is demonstrated in the time-domain that the low-pass NGD effect enables the UDCF cell to generate advanced output with sinc waveform input voltages.

Diakoptics Modelling Applied to Flying Bird-Shape NGD Microstrip Circuit

Abstract: This brief develops a diakoptics modelling of a flying bird topology constituted by interconnected piece-wises of admittance or Y-matrices. The diakoptics principle is established with passive system teared into several simplex elements as transmission and coupled lines (TLs and CLs). After introduction of subsystem Y-matrix, the global system Y- and S-matrices are established. To verify the model effectiveness, parametric analyses enabling to understand bandpass negative group delay (NGD) behavior of the flying bird topology. Furthermore, a microstrip circuit is designed, fabricated and tested. The modeled, simulated and measured NGD circuit responses are in excellent agreement. NGD value about −2.2 ns under transmission and reflection coefficients better than −2 dB and −13 dB is measured around 1.15 GHz.

Negative Group Delay Theory on Li Topology

Abstract: This paper investigates an innovative negative group delay (NGD) theory of “li” geometrical shape topology. The li-topology is an outstandingly simple and fully distributed circuit comprised of a coupled line (CL). The li S-parameter model taking into account the CL coupling coefficient, delay and attenuation is established. The NGD analysis showing the possibility to generate NGD condition with respect to the li topology parameters is developed. The NGD characteristics as NGD value, center frequency, bandwidth, transmission and reflection coefficient are expressed. The li-NGD theory is validated with two proofs-of-concept implemented in microstrip technology. Calculated models, simulations and measurements are in good correlation. As expected, bandpass NGD presenting center frequency at approximately 2.56 GHz and 0.92 GHz with NGD level of approximately −0.9 ns and −3.7 ns were realized with the small and large li prototypes. Outstanding time-domain analyses explaining the bandpass NGD meaning, with innovatively low attenuation output, were also presented. The time-domain results highlight li-output pulse signal envelopes in time advance without violating the causality.

Modeling of Magnetic Near-Field Radiated by Electronic Devices Disturbed by Transient Signals with Complex Form

Abstract: For the safety and reliability of modern hybrid electronic systems in function of the increase of complexity and density integration, relevant modeling methods of near-field (NF) radiation are necessary. This article develops a time-frequency modeling method of electromagnetic (EM) NF emitted by electronic devices excited by transient pulse current. The modeling method is originally flexible to fast switching disturbances propagating in the mixed-systems. The model is based-on the ultra wide band (UWB) model of EM NF maps using a set of elementary EM dipoles. An innovative algorithm for generating a simple reduced model is established. Then, by considering the convolution between the signals exciting the circuit and the UWB model introduced, transient radiation models are realized. The method developed was validated with the magnetic NF radiated at some mm above the microstrip planar DUT. The UWB model effectiveness was verified in RF baseband from DC to 100 MHz. Then, NF map time-dependent model emitted by the circuit excited by a microwave signal modulating 0.9 GHz carrier with 0.6 GHz - 1.2 GHz frequency band is also validated. As expected, good agreements between simulations, measurements and the models investigated are observed for any form of excitation current.

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.