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.

Frequency-independent active phase shifters for UWB applications

Abstract: This paper describes an active phase shifter, which exhibits a frequency-independent phase shift over the ultra-wideband (UWB) frequency range. The design of this pure phase shifter relies on the use of a negative group delay (NGD) circuit. The topology of the active NGD cell is based on a Field Effect Transistor in cascade with a series resonant network. A 90°±5° phase shifter with a single NGD stage was designed, at first, and implemented in hybrid microstrip technology; its measurements showed a 75% relative bandwidth and validated the proposed approach. Then, a compact pure phase shifter with a multi-stage NGD cell was designed. It was aimed at meeting specifications in the UWB frequency range, i.e. 3.1–10.6 GHz (110% relative band). Over this band, the corresponding simulation results showed a constant transmission phase of −45°±3°, an insertion gain from 2 to 5.5 dB and insertion losses better than 9 dB.

Low-Pass NGD Voice Signal Sensoring With Passive Circuit

Abstract: Nowadays, the speech signal processing is still challenging with the multimedia ubiquity. Classical signal processing techniques as filtering were developed for the speech enhancement to overcome unintentional effects as the propagation channel. However, the delay effect remains an open challenge for audio signal processing engineers. A voice/song signal (VSS) prediction is investigated theoretically and experimentally in this paper. This VSS engineering allows to predict an arbitrary waveform signal by using a lowpass negative group delay (NGD) function. This outstanding function presents the VSS advance properties when its parameters are matched with the operated signals. This NGD engineering analytical approach is described with the audio signal processing. The low-pass NGD analysis and property are deeply investigated with two NGD RC-and RL-passive cells. NGD transient study is performed with parametric analytical signals presenting raised cosine waveform. The introduced VSS NGD sensoring is verified with experimental real-time tests of microphone VSS generator. VSS time-advance of approximately 50 μs was observed with a good agreement between simulations and measurements.

X-band negative group-delay lossy stub line

Abstract: This study investigates the negative group delay (NGD) passive circuit constituted by a fully distributed parallel stub line. The proposed S-parameter modelling is developed. The transmission parameter band-pass NGD function identification is described. The NGD characterisation is established by determination of the NGD level and bandwidth in function of the stub line parameters. It was analytically found that with a basic cell consisted of single stub line, the insertion loss is usually degraded to reach significant figure-of-merit which is obtained with the NGD level-bandwidth product. As a solution, it is shown that this insertion loss can be improved with the consideration of matching network. As proof-of-concept (POC), microstrip distributed circuits printed on the flexible Kapton substrate without lumped element were synthesised, designed and fabricated. The theoretical, simulated and measured results are in good correlation. As expected, band-pass NGD behaviours centred beyond 10 GHz were observed. The POC generates NGD level of about -1.5 ns over the NGD bandwidth 0.65 GHz. In the future, thanks to the theoretical approach simplicity and the topology integrability, the NGD principle can be potentially useful for the improvement of RF/microwave circuits.

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.