Showing papers by "Blaise Ravelo published in 2013"

Analysis of multi‐gigabits signal integrity through clock H‐tree

Abstract: The H-tree interconnect network is frequently used for the clock signal sharing in the microelectronic systems. Due to the increase of complexity and operating processing data speed, these interconnect effects can bottleneck the technological advancement. Hence, more accurate interconnect modelling methods are necessary for electronic designers. For this reason, a simple and accurate ultra-wide band (UWB) model of multilevel distributed interconnection clock trees as a single input multiple outputs (SIMO) system is developed in this article. Very accurate single input single output (SISO) model transfer functions are derived. This method allows the signal integrity prediction regarding the distributed H-tree characteristics including the source and load impedances. In order to demonstrate the relevance of model developed, analyses of two- and three-level tree networks were performed. Distributed H-tree realistic devices formed by sub-millimetre physical length lines for applications for standardised Printed Circuit Board (PCB) interconnections were experimented numerically. The piece of lines constituting the trees is modelled by UWB RLCG network from DC to 8 GHz which takes into account the frequency dispersions and dielectric loss effects. Thus, excellent correlations between simulations and the results from the models proposed were observed both in frequency and time domains regarding 2.5 Gbits/s clock input. Copyright © 2012 John Wiley & Sons, Ltd.

New Behavioral Modeling of EMI for DC Motors Applied to EMC Characterization

Abstract: This paper is dealing with the characterization of the electromagnetic compatibility of the direct current (dc) motors. It acts as the complements of the works achieved recently for the modeling of dc motor impedances. The contact mechanisms between the brushes and the collector blades which cause the electromagnetic interferences (EMIs) are explained and modeled. Knowing the operating conditions of the current intensity, voltage, and speed, EMIs are measured and analyzed in radio frequencies from 100 kHz to 108 MHz. The behavioral model proposed is based on Norton's equivalent circuit where the motor is assumed as a current generator representing the EMI source, associated in parallel with its impedance model. Specific identification methods are used to quantify the EMI model parameters. It is shown that the model is in good correlation with the measurement. The model was applied for estimating the conducted EMI generated by a dc motor with its filters, and then, validations with different dc motors were performed.

Neutralization of LC- and RC-Disturbances with Left-Handed and NGD Effects

Abstract: This paper focus is on the neutralization technique of the unwanted physical disturbances in the radio frequencies (RF) and digital electronic structures. Most of parasitic effects induced in these systems can be modeled by RC- and LC- passive networks. For canceling these disturbing effects, we can proceed with the transfer function neutralization in the considered operating frequency bands. This neutralization concept is developed by using first, a left-handed (LH) and negative group delay (NGD) circuits inspired from metamaterials. The fundamental theoretical approach illustrating the RC- and LC-effects transfer function neutralization is described. Synthesis relations enabling to determine the elements of the LH and NGD circuit correctors in function of the perturbation parameters are established. Numerical and experimental demonstrators are presented to validate the technique proposed. This later is particularly useful for the improvement of the analogue and digital signal integrity degraded by electromagnetic interferences.

Methodology of elementary negative group delay active topologies identification

Abstract: This work introduces a fundamental methodology enabling to identify the elementary negative group delay (NGD) topologies using transistors. These circuits are particularly beneficial compared to the other existing NGD topologies, with its flexibility to operate in ultra wideband (UWB), to compensate losses and potentially integrable. The basic families of NGD topologies obtained from the association of passive and active four-port networks are presented. The NGD existence condition is given. Based on this condition, the simplest NGD active cells are identified. After the analysis of passive networks formed by R, L and C components, first-order transfer functions of innovative elementary NGD cells are established. Then, similar to the classical circuits as the filters and amplifiers, synthesis relations for the design of integrable NGD topology with no self-element are introduced. To illustrate the relevance of the theoretic concept, a proof of concept was proposed. Finally, discussions on the applications of NGD circuits are offered in the conclusion.

Synthesis of RF Circuits with Negative Time Delay by Using LNA

Abstract: A demonstration of the negative time-delay by using active circuit topologies with negative group delay (NGD) is described in this paper. This negative time delay is realized with two different topologies operating in base band and modulated frequencies. The first NGD topology is composed of an RL-network in feedback with an RF/microwave amplifier. Knowing the characteristics of the amplifier, a synthesis method of this circuit in function of the desired NGD values and the expected time advance is established. The feasibility of this extraordinary physical effect is illustrated with frequency- and time-domain analyses. It is shown in this paper that by considering an arbitrary waveform signal, output in advance of about 7 ns is observed compared to the corresponding input. It is stated that such an effect is not in contradiction with the causality. The other NGD topology is comprised of a microwave amplifier associated with an RLC-series resonant. The theoretical approach illustrating the functioning of this NGD circuit is established by considering the amplifier S-parameters. Then, synthesis relations enabling to choose the NGD device parameters according to the desired NGD and gain values are also established. To demonstrate the relevance of the theoretic concept, a microwave device exhibiting NGD function of about -1.5 ns at around 1.19 GHz was designed and analyzed. The NGD device investigated in this paper presents advantages on its faculty to exhibit positive transmission gain, the implementation of the bias network and matching in the considered NGD frequency band.

Assessment of 50%-Propagation-Delay for Cascaded PCB Non-Linear Interconnect Lines for the High-Rate Signal Integrity Analysis

Abstract: This paper presents an enlarged study about the 50-% propagation-time assessment of cascaded transmission lines (TLs). First and foremost, the accurate modeling and measurement technique of signal integrity (SI) for high-rate microelectronic interconnection is recalled. This model is based on the reduced transfer function extracted from the electromagnetic (EM) behavior of the interconnect line RLCG-parameters. So, the transfer function established takes into account both the frequency dispersion effects and the different propagation modes. In addition, the transfer function includes also the load and source impedance effects. Then, the SI analysis is proposed for high-speed digital signals through the developed model. To validate the model understudy, a prototype of microstrip interconnection with w = 500 µm and length d = 33 mm was designed, simulated, fabricated and tested. Then, comparisons between the frequency and time domain results from the model and from measurements are performed. As expected, good agreement between the S-parameters form measurements and the model proposed is obtained from DC to 8 GHz. Furthermore, a de-embedding method enabling to cancel out the connectors and the probe effects are also presented. In addition, an innovative time-domain characterization is proposed in order to validate the concept with a 2.38 Gbit/s-input data signal. Afterwards, the 50-% propagation-time assessment problem is clearly exposed. Consequently an extracting theory of this propagation-time with first order RC-circuits is presented. Finally, to show the relevance of this calculation, propagation-time simulations and an application to signal integrity issues are offered.

Near-field coupling model between PCB and grounded transmission line based on plane wave spectrum

Abstract: This article presents an explicit model of electromagnetic (EM) coupling between electronic circuits and metallic wire placed above the ground plane. The model is based on the interaction between the EM near-field (NF) that has been treated with plane wave spectrum (PWS) and the Taylor model. The routine process illustrating the methodology is addressed is this article. The practicability of the model developed was upheld with different analytical and real demonstrators. First, the NF coupling between a straight transmission line (TL) and 1 GHz Wilkinson power divider (PWD) designed and implemented in planar technology was provided. Subsequently, simulations with a powerful commercial tool and measurements from 0.2 GHz to 2 GHz revealed a good agreement between the coupling voltages from the proposed model. As a second proof of concept, a printed circuit board incorporating a 40 MHz RF oscillator was placed 5 mm above the grounded TL. Once again, coupling voltages matched measurements were observed with magnitude relative difference lower than 5 dB. The hereby model presents huge benefits not only in terms of flexibility in the design process but it can also be run with very less computation time compared to the existing standard simulators. The model can be potentially a good candidate for investigating complex systems EMC engineering.

Fast estimation of high-speed signal integrity for coupled PCB interconnects

Abstract: A predictive signal integrity (SI) model of coupled PCB interconnects for high-speed application is stated. It is derived from the analytical modeling of coupling matrices between neighboring transmission lines (TLs). The overall ABCD matrix is regenerated and manipulated by using the modal approach. Afterwards, the S-parameters of the structure are substantially extracted for forecasting the behavior SI propagating along the underlying interconnections. In order to reveal the effectiveness of the fast model developed, EM/circuit co-simulations with commercial tool were performed both in the frequency- and time-domains with 1Gbps-rate-mixed signals. Different configurations were undertaken. The validity of the centimeter length coupling model hereby with respect to the geometrical parameters of the interconnect structures is also investigated. Finally, potential applications for high-speed systems are discussed, especially for non-symmetrical coupled lines and microelectronic interconnects.

Electrical performance modeling of unbalanced comb tree networks on advanced PCB interconnects for high-rate clock signal distribution

Abstract: Usually, the routing process is made by non-specialists in electrical simulation that only meet the requirement of the standards. The aim of this work is to supply a new tool dedicated to assess the quality of the tree network routing. An innovative modeling method of advanced unbalanced interconnections called “comb tree” for distributing high speed clock signals is featured. The flow work summarizing the routine process of new design rule is established to enhance the performance of advanced packages for high speed circuits. The analytical approach for extracting the voltage transfer function corresponding to the electrical signal paths in function of tree branch parameters is fundamentally inspired from SIMO/SISO electrical circuit analogy. Doing so, the wideband characteristic impedances and propagation constants of elementary lines constituting the tree are extracted from geometrical and physical properties. A PCB prototype of unbalanced comb tree network over FR-4 substrate has been designed and manufactured for the experimental verification. Then, frequency analyses of different VTFs have been carried out. Less than 1dB of error has been found within the DC-3GHz bandwidth and less than 4 dB within 3-10GHz. In addition, time-domain analyses with 2 Gbps input signal has been realized. Excellent agreements between transient simulations and the proposed model have been established. The model developed is potentially useful for predicting the signal integrity and optimization process of unbalanced advanced PCB and on-chip tree interconnects.

Distributed model of two-level asymmetrical PCB interconnect tree

Abstract: A distributed behavioral model of two-level 1:n (1-input and n-outputs) asymmetrical interconnect tree network is explored Based on circuit approach, theoretic analysis illustrating the mechanism of the underlying model extraction is described The asymmetrical tree model is yielded from an innovative single input multiple output/single input single output (SIMO/SISO) transform For predicting the signal responses each outbranch of the tree, the voltage transfer function (VTF) corresponding to any electrical path from the input to the output node under interest is mathematically expressed To verify the relevance of the behavioral method proposed, 1:3 asymmetrical two-level distributed tree network was designed in microstrip planar circuit Then, numerical validations were performed both in the frequency- and time-domains It was pointed out that good accordance between the VTF frequency responses of tested tree signal paths from DC to 4GHz was confirmed The behavioral two-level model developed is benefited not only in term of simplicity and computation speed but also to its flexibility to complex shape of asymmetrical interconnect trees The model could be useful for the high-speed electronic circuit manufacturers for predicting the signal integrity through interconnect PCB trees

Numerical modeling of high-speed microelectronic interconnects for the signal integrity analysis

Abstract: Facing to the incessant increase of data processing speed, the microelectronic interconnections play an important role during the design of the integrated system. As the interconnection signal delays dominate widely gate delays, accurate interconnection model is needed. Indeed, direct mathematical calculation of distributed interconnection transient responses is generally very complicated. For this reason, one proposes to develop a numerical modeling method of prediction of the signal integrity (SI) propagating though the distributed interconnection lines. For that, the microelectronic interconnect lines are assumed as comprised of periodical lumped L-cells cascaded. Via L-cell transfer matrix analysis, it is established how to determine the equivalent global transfer function versus the lumped cell element number n. To verify the relevance of developed model, RC-line with mm-length excited by square-wave-pulse with 10 Gbits/s rate was investigated in function of n and the interconnect line per unit length parameters. As results, transient responses perfectly well-correlated to the SPICE-computations were found with relative errors lower than 5% for n higher than 20. In addition, values of propagation delays and signal attenuations closed to SPICE-models were evidenced for various interconnection network parameters. The computation-time for the execution of the proposed method algorithm was only of tens µs.