Showing papers by "Blaise Ravelo published in 2014"

Similitude between the NGD function and filter gain behaviours

Abstract: This paper deals with the similitude between the behaviours of linear filter gain and negative group delay NGD function. The transposition method of low-pass/high-pass, low-pass/band-pass and low-pass/band-stop NGD circuits is established. To the best of the author knowledge, it acts as the first paper devoted on the NGD function generalized theory. The introduced transform relationships simplify the synthesis of any NGD circuits from simple elementary low-pass NGD topologies. Families of innovative NGD topologies are identified. To verify the relevance of the concept proposed, frequency- and time-domain analysis results from realistic proofs of concept demonstrating the feasibility of developed NGD transforms were performed. Thanks to the NGD phenomenon, the possibility of the ultra-wideband pulse signals propagating in time-advance is verified. Finally, potential applications of NGD circuits are discussed. Copyright © 2013 John Wiley & Sons, Ltd.

Distributed NGD active circuit for RF-microwave communication

Abstract: This paper is aimed to the investigation on innovative distributed negative group delay (DNGD) circuits for RF communication. Thanks to the analogy between the lumped and distributed circuits, NGD circuit topologies were identified. By using the S -parameter theory, analysis and synthesis methods of these topologies are proposed. The DNGD circuits developed are mainly comprised of a transistor combined with a series resistance ended by a stub. Then, synthesis relations enabling to determine the NGD circuit parameters from the desired NGD and gain values are established. As application, an active phase shifter (PS) operating independently with the frequency based on the cascade of PGD and NGD devices was synthesized. First, an NGD PS with transmission phase of (135 ± 5)° around 2.56 GHz over the bandwidth of about 1.02 GHz was obtained. Then, a two-stage DNGD PS exhibiting 90° with ±10° flatness from 4.1 GHz to 6.8 GHz was designed. The DNGD circuit presented can be used in various telecommunication areas notably for correcting RF/numerical signal delays in the RF-microwave analogue-digital devices.

Fully Time-Domain Scanning of EM Near-Field Radiated by RF Circuits

Abstract: This paper deals with planar scanning technique of electromagnetic (EM) near-fleld (NF) emitted by electronic printed circuit boards (PCBs) fully in the time-domain (TD). The proposed EM scanning metrology is essentially based on the NF test bench available at the IRSEEM laboratory. It comprises motorized mechanical structures for moving the probe interconnected to electronic measurement instruments and controlled by a driver PC. The synoptic of the test bench is presented and technically examined. The characteristics of difierent elements constituting the measurement chain of the TD test bench understudy are described. The NF metrology developed is originally focused on the measurement of time-dependent magnetic fleld H(t) dedicated to the radiated emission electromagnetic compatibility (EMC) applications. An innovative calibration technique of the loop probe for detecting H(t) is established in order to ensure the post processing and extraction of the measured NF data. Then, validations were carried out via comparison with difierent simulations run with standard commercial tools. Mathematical analyses were also conducted for the improvement of the measurement post processing. To realize the mapping of time-dependent EM fleld components, a software interface edited with the graphical language LabVIEW was emulated to synchronize the probe displacement and the data acquisition. An UWB amplifler with average gain about 30dB from DC to 300MHz was designed and fabricated in order to decrease the measurement noise and to improve the quality of measured signals. As results of the study, TD NF mapping is demonstrated successfully by measuring the EM radiation emitted by electronic planar circuits. The technique developed is extremely useful in the fleld of EMC engineering for predicting the transient perturbations susceptible to degrade electronic functions in complex systems encountered usually for the automotive and aeronautic applications.

Asymmetrical PCB Interconnect Tree Modelling with Coupling Effect

Abstract: The paper describes integrity analysis of the signal propagating on asymmetrical tree with coupling from neighboring lines. Theoretical principle illustrating the modelling methodology and the developed routine algorithm is mathematically established. The developed model was applied to 2:1 asymmetrical microstrip tree with neighboring single lines at 10-to-100µm distance. Frequency- and time-domain analyses were conducted to check the coupling influence onto the signal distribution tree due to the substrate dielectric dispersion using broadband model. Examples of applications from DC to 10GHz were investigated to evaluate the influence of the coupling on the asymmetrical tree responses. It was shown that ringing effects and distorted signals were occurring from the two tree branch outputs. Furthermore, time-domain analyses were performed with 8-bits high speed input signal data with 0.5 Gbps rate. It was found that the signal quality was degraded and the amplitude of the shared signals was slightly affected by the coupling.

Analysis of Excitation Pulsed Signal Propagation for Atom Probe Tomography System

Abstract: The purpose of this paper is on the behavioral modelling of surge voltage pulses used in Atom Probe Tomography. After brief description of the atom probe functioning principle, we examine the excitation electrical pulse signal integrity along the electric pulser (E-pulser) feeding line modelling with respect to the IEC1733/04 standard. This feeding electric line is ended by cylindrical via ground to control the ion emission. By using the transmission line (TL) ultra-broadband RLCG model, the propagating pulsed signals degradation is predicted. The signal propagation was analysed in both frequency and time domains by taking into account the substrate dispersion. The wideband frequency behaviours of the surge signal along the feeding line were examined from DC-to-2GHz. In addition, by considering pulse surge signals with pulse-width and rise-/fall-time parameters (T1 = 9ns, tr1 = tf1 = 1:6ns) and (T2 = 30ns, tr2 = 4ns/tf2 = 18ns), the transient responses from 5cm-to- 20cm length TL are characterized. It was shown that the excitation pulse was signiflcantly distorted. It was emphasized that the operated signal delay varies from 0.3ns-to-1.5ns in function of the via capacitor value. The time-dependent radiated E-fleld on the performance of the atom probe system which enables to characterize the nature of tested materials (ions or atoms) is discussed. The presented analysis approach is particularly useful for E-pulser integrated in measurement scientiflc instruments as Atom Probe Tomography time of ∞ight optimisation, a nano-analysing technique that uses ultra-sharp high vacuum pulse to induce controlled erosion of samples. In this application, the excitation voltage pulse integrity during the propagation is required in order to improve the measurement instrument performances.

Analysis of complex environment effect on near-field emission

Abstract: The article is dealing with uncertainty analyses of radiofrequency circuits electromagnetic compatibility emission based on the near-field/near-field (NF/NF) transform combined with stochastic approach. By using 2D data corresponding to electromagnetic (EM) field (X=E or H) scanned in the observation plane placed at the position z0 above the circuit under test (CUT), the X field map was extracted. Then, uncertainty analyses were assessed via the statistical moments from X component. In addition, stochastic collocation based was considered and calculations were applied to planar EM NF radiated by the CUTs as Wilkinson power divider and a microstrip line operating at GHz levels. After Matlab implementation, the mean and standard deviation were assessed. The present study illustrates how the variations of environmental parameters may impact EM fields. The NF uncertainty methodology can be applied to any physical parameter effects in complex environment and useful for printed circuit board (PCBs) design guideline.