Showing papers by "Blaise Ravelo published in 2011"

Transient response characterization of the high-speed interconnection rlcg-model for the signal integrity analysis

Abstract: This paper is devoted on the characterization method of RF/digital PCB interconnections for the prediction of the high- speed signal transient responses. The introduced method is based on the use of the interconnection line RLCG-model. Theoretical formulae enabling the extraction of the electrical per-unit length parameters R, L, C and G in function of the interconnection line physical characteristics (width, length, metal conductivity, dielectric permittivity ...) are established. Then, by considering the second order approximation of the interconnection RLCG-model transfer matrix, the calculation process of the transient responses from the interconnection system transfer function is originally established. To demonstrate the relevance of the proposed model, microwave- digital interconnection structure comprised of millimetre microstrip line driven and loaded by logic gates which are respectively modelled by their input and output impedances was considered. Then, comparisons between the SPICE-computation results and those obtained from the proposed analytical model implemented in Matlab were made. As results, by considering a periodical square microwave-digital excitation signal with 2Gbits/s rate, transient responses which are very well- correlated to the SPICE-results and showing the degradation of the tested signal fldelity are observed. The numerical computations conflrm that the proposed modelling method enables also to evaluate accurately the transient signal parameters as the rise-/fall-times and the 50% propagation delay in very less computation time. For this reason, this analytical-numerical modelling method is potentially interesting for the analysis of the signal integrity which propagates

Investigation on Microwave Negative Group Delay Circuit

Abstract: In this article, a fundamental analytical approach and experimental verification of a radio frequency active circuit capable of exhibiting negative group delay at microwave wavelengths are presented. By using the S-parameter theory, basic properties and characteristics of the negative group delay circuit under study are established. To highlight the functionality principle of this innovative circuit, time-domain investigations based on ultra-wide-band pulse signal tests are performed. Then, the mechanism of propagating output signal envelopes in time advance compared to the input is demonstrated. To validate this concept, a prototype of a negative group delay device was designed, fabricated, and tested. Experimental results in good agreement with theory and simulation were obtained. In the frequency domain, a negative group delay of about −2.5 ns with amplification of 2 dB was measured at around 622 MHz. Due to this negative group delay effect, envelope advance of about −1.5 ns was observed by co...

Cancellation of Delays in the High-Rate Interconnects with UWB NGD Active Cells

Abstract: This paper is devoted to the extension of the interconnect effect equalization concept with NGD circuits for UWB applications. First, RC interconnect effects are considered. It was found that by cascading with the NGD structure, the propagation delay of the considered rate 4 Gbps signal was compensated for about 98-%. Then, the feasibility of the technique by taking into account the interconnection inductive effect with RLC-model is also investigated. It was demonstrated that the technique proposed brings opportunities to compensate for simultaneously the propagation delay and distortions. Then, the application of the proposed technique for the optical interconnect correction is discussed.

Baseband NGD circuit with RF amplifier

Abstract: This presented report deals with the synthesis of baseband negative group delay (NGD) RF circuits. A theoretical approach based on the S-parameter analysis is presented. The NGD circuit synthesis formulae according to the desired gain value, NGD level and bandwidth are established. To validate the theoretical approach, a two-stage NGD device employing LNAs was investigated. Baseband NGD with minimal value below −1 ns with 400 MHz frequency bandwidth was found. The synthesised circuit presents a gain higher than 5 dB. To highlight the functionality of the NGD effect, time-domain analysis was performed. The NGD circuit allows the reduction of signal pure delays caused by telecom devices and is useful for the correction of interleaved symbols in RF/digital numerical systems.

An FET-based microwave active circuit with dual-band negative group delay

Abstract: Recent studies proved that certain electronic active circuits are capable to exhibit simultaneously a negative group delay (NGD) and amplification in microwave frequency bands. One of the simplest topologies generating this counterintuitive NGD function effect is formed by a series RLC-network in cascade with a transistor. By using this cell, similar to the classical electronic functions, dual-band NGD microwave devices with loss compensation possibility can be designed. Theoretic demonstrations concerning the theory of the NGD circuit considered are presented. The dual-band NGD concept feasibility is concretely illustrated by an example of EM/circuit co-simulations. So, in frequency domain, dual-band NGD with minimal values of about -1 ns was observed simultaneously within two frequency bands centered at about 1.05 GHz and 2.05 GHz. To highlight the functioning of the hybrid device considered, time-domain analysis showing the RF/microwave signal advancement is performed. As application, the concept investigated can be envisaged for data synchronization in multi-channel wireless communication systems eventually degraded by undesired EMI effects.

Demonstration of negative signal delay with short-duration transient pulse

Abstract: This paper introduces theoretic and experimental analyses of short-duration pulse propagation through a negative group delay (NGD) circuit. The basic analysis method of this electronic circuit operating in baseband and microwave frequencies is investigated. Then, its electrical fundamental characteristics vis-a-vis transient signals are developed. To validate the theoretic concept, planar hybrid devices with one- and two-stage NGD cells were designed, simulated, fabricated and tested. Transient analyses with ultra-wide band (UWB) pulse signals with different widths are realized. Then, experimental results in good agreement with the theoretical predictions were observed. Consequently, group delay going down under −2.5 ns is evidenced in baseband frequency up to 63 MHz with one-stage NGD cell. In time-domain, a Gaussian pulse in advance of about t 0 = −1.5 ns or 20% of its half-height time-width was measured. This corresponds to a negative group velocity of about v g = L / t 0 = −0.13 c ( L is the physical length of the tested device and c is light speed in the vacuum). More significant NGD value over 100-MHz bandwidth is stated with two-stage NGD cells. This results in a Gaussian pulse peak advance of about −5 ns (raising a group velocity of about v g = −0.12 c ) or 31% of its half-height time-width. Finally, some potential applications based on the NGD function are discussed.

Synthesis of frequency-independent phase shifters using negative group delay active circuit

Abstract: This article describes a synthesis method dedicated to the design of frequency-independent phase shifters (PSs). This innovative PS structure consists in a transmission line cascaded with a negative group delay (NGD) active circuit so that the absolute constant group delays generated by both of them are identical but of opposite signs. So, in principle, it exhibits a constant overall phase and a group delay close to zero. Broadband linear positive phase slopes are obtained through use of an NGD active circuit whose characteristics are recalled prior to the extraction of the PS synthesis relations. The design and simulations of a PS of compact size are reported. The experimental results confirm the expected frequency-independent transmission-phase value of 145° ± 10° with an insertion gain of 2 ± 2 dB over a 160% relative frequency band. At last, future prospects allowed by the specific properties of this PS are presented. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE , 2010. © 2011 Wiley Periodicals, Inc.

Study of high-frequency electromagnetic transients radiated by electric dipoles in near-field

Abstract: The study investigates transient electromagnetic (EM) radiation in the near-field zone of a system of electric dipoles and the usage of the plane wave spectrum (PWS) concept for extraction of a 3-D field from 2-D measurements. Both aspects are important in the modelling and characterisation of radiated emissions in electromagnetic compatibility applications, which are extended here to time domain. Analytical expressions for a set of dipoles excited by short-duration Gaussian pulses, which in the author's approach are used to model EM radiation, are presented and implemented into a Matlab program to calculate the time-dependent distributions of the three electric field components Ex(t), Ey(t), Ez(t). These results are then used to verify the new technique of extraction of the time-domain component Ez(t) of the electric field from measurements of the two other components, Ex(t) and Ey(t). The details of the technique, based on PWS method applied to the time domain, are presented. Very good agreement between the extracted and analytically calculated fields has been achieved. Further verification and comparison has been done by the simulation in the time domain of the system of dipoles using commercial 3-D EM software.

Time-domain near-field/near-field transform with PWS operations

Abstract: This article deals with the development of computation method dedicated to the extraction of the transient EM-near-field at certain distance from the given 2D data for the baseband application up to GHz As described in the methodological analysis, it is based on the use of fft combined with the plane wave spectrum (PWS) operation In order to verify the efficiency of the introduced method, a radiating source formed by the combination of electric dipoles excited by a short duration transient pulse current with a spectrum bandwidth of about 5 GHz is considered It was shown that compared to the direct calculation, one gets the same behaviors of magnetic near-field components H x , H y and H z with the presented extraction method, in the planes placed at {3 mm, 8 mm, 13 mm} of the initial reference plane To confirm the relevance of the proposed transform, validation with a standard commercial tool was performed In future, we envisage to exploit the proposed computation method to predict the transient electromagnetic (EM) field emissions notably in the microwave electronic devices for the EMC applications

Investigation on the microwave pulse signal compression with ngd circuit

Abstract: This paper demonstrates the exhibition of pulse compres- sion from an electronic circuit with negative group delay (NGD). This circuit consists of a fleld efiect transistor (FET) cascaded with shunt RLC network. Theoretic and experimental investigations have proved that, at its resonance frequency, the group delay of this circuit is al- ways negative. The present study shows that around this resonance, it presents a gain form enabling to generate pulse compression. To validate this concept, as proof-of-principle, devices with one- and two- stages FET were implemented and tested. Measurements of the one- stage test device evidenced an NGD of about i2:5ns and simulta- neously with 2dB ampliflcation operating at 622MHz resonance fre- quency. In the frequency domain, in the case of a Gaussian input pulse with 40MHz frequency standard deviation, this resulted in 125% ex- pansion of pulse width compared to the input one. In time domain, simulations showed that the compression was about 80% in the case of an input Gaussian pulse with 4ns standard deviation. With the other prototype comprised of two-stage NGD cell, the use of a sine carrier of about 1.03GHz allowed to achieve 87% pulse width compression.

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.

Computational method of extraction of the 3D E-field from the 2D H-near-field using PWS transform

Abstract: The paper introduces a computational method of 3D electric field extraction (E-field) from the 2D magnetic field components H x and H y measured in near zone. The method is based on the exploitation of the Maxwell-Ampere relation combined with the plane wave spectrum (PWS) approach. The proposed technique is validated on the example of an electromagnetic (EM) field radiated by a set of magnetic dipoles placed in the horizontal plane, as used in some modeling approaches of radiated EMC emissions. The proposed technique is therefore useful in EMC applications, simplifying the measurement process.

E-field extraction from Hx- and Hy- near field values by using plane wave spectrum method

Abstract: This paper deals with a technique for calculating the 3D E -field components knowing only the two components ( H x and H y ) of the H -field in near-zone. The originality of the under study technique lies on the possibility to take into account the evanescent wave influences. The presented E -field extraction process is based on the exploitation of the Maxwell-Ampere relation combined with the plane wave spectrum (PWS) method. The efficiency of the proposed technique is evidenced by comparing the E -field deduced from H -field and the own E -field radiated by the association of electrical- and also magnetic- elementary dipoles in different configurations by using Matlab text programming environment. In addition, as a concrete demonstrator, the concept was also validated with the computation of EM-wave radiated by an open-end microstrip transmission line. As result of comparison, very good agreement between the exact E -field and that one extracted from the H -field was realized by considering the near-field scanned at the height, z = 5 mm and 8 mm above the under test structure at the operating frequency, f = 1 GHz. The presented technique can simplify the difficulties about the E -near-field measurement in EMC applications.

Experimental investigation on the power electronic transistor parameters influence to the near-field radiation for the emc applications

Abstract: With the increases of the module integration density and complexity in electrical and power electronic systems, serious problems related to electromagnetic interference (EMI) and electromagnetic compatibility (EMC) can occur. For the safety, these disturbing efiects must be considered during the electronic equipment design process. One of the concerns on EMC problems is induced by unintentional near-fleld (NF) radiations. The modeling and measurement of EM NF radiations is one of the bottlenecks which must be overcome by electronic engineers. To predict the unwanted difierent misbehaviors caused by the EM radiation, NF test benches for the reconstitution of scanning maps at some millimeters of electrical/electronic circuits under test were developed at the IRSEEM laboratory. Due to the di-culty of the design with commercial simulators, the prediction of EM NF emitted by active electronic systems which are usually based on the use of transistors necessitates more relevant and reliable analysis techniques. For this reason, the main focus of this article is on the experimental analysis of EM NF radiated by an MOSFET transistor with changing electrical parameters. Descriptions of the experimental test bench for the EM map scan of transistors radiation are provided. This experimental setup allows not only to detect the EM NF emission but also to analyze the in∞uence of the excitation signal parameters

Investigation of reduced models of capacitive loaded interconnects for the high-speed SI applications

Abstract: The paper presents a reduced modeling method of a microstrip interconnect for the signal integrity (SI) applications. First- and second- order polynomial models of interconnects based on distributed RLCG model of a transmission line are investigated. Model accuracies are compared with exact circuit/EM co-simulations for a typical high-speed 20 µm-wide microstrip interconnect on Alumina substrate for varying interconnect lengths between 1 and 10 mm and for signal data rates between 1 and 10 Gbit/s. It is shown that the second-order model has a relative amplitude and phase errors lower than 1% from DC to 40 GHz. Also, the second-order model predicts very well the time-domain response to a pulse signal, making it suitable for the accurate prediction of the degradation of RF/digital signals in the high-speed integrated systems.

Analogue Behavioral Modeling of GTO

Abstract: An analog behavioral model of high power gate turn-off thyristor (GTO) is developed in this paper. The fundamental methodology for the modeling of this power electronic circuit is based on the use of the realistic diode consideration of non-linear junctions. This modeling technique enables to perform different simulations taking into account the turn-on and turn-off transient behaviors in real-time. The equivalent circuits were simulated with analog software developed in our laboratory. It was shown that the tested simple and compact model allows the generation of accurate physical characteristics of power thyristors under dynamic conditions. The model understudy was validated with analog simulations based on operational amplifier devices.

Déphaseur "pur" UWB

Abstract: Dans cet article, une methode de synthese de dephaseur pur actif utilisant un circuit a temps de propagation de groupe (TPG) negatif est presentee. Une phase en transmission independante de la frequence (dephaseur pur) sur de larges bandes de frequence est obtenue grâce au circuit a TPG negatif et a sa pente de phase positive. En effet, ce circuit est associe ici a une simple ligne de transmission dont la pente de phase est identique mais de signe oppose pour obtenir au final une phase constante. Les mesures d'un dephaseur realise par cette methode confirment une phase constante de 145°±10 ainsi qu'un gain de 2dB±2 sur une bande relative de 160%. Son comportement non-lineaire est egalement etudie. Ce nouveau principe a permis de concevoir un dephaseur UWB multi-etages dont la phase est constante a -45° de 3.1 a 10.6 GHz. Les limites et avantages de ces dephaseurs sont finalement analyses ainsi que les applications associees.