Blaise Ravelo

Active Microwave Circuit With Negative Group Delay

In this letter, we report on the design, simulation and implementation of an active negative group delay circuit that operates at 1 GHz with a group delay and a gain, respectively, around 2 ns and 2 dB. Analytical formulas are proposed to demonstrate that the adopted topology is able to simultaneously achieve negative group delay (NGD) and gain while fulfilling active device constraints. The theoretical and simulated results are both validated by frequency measurements of a two-stage active microwave circuit.

Transient Response Characterization of the High-Speed Interconnection Rlcg-Model for the Signal Integrity Analysis

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 considering a pulse signal with a half-height full-width of 10 ns, which modulates a sine carrier with a frequency of 622 MHz. The negative group delay topology presented is potentially useful for the compensation of radio frequency/microwave signal delays.

Broadband balun using active negative group delay circuit

In this paper, a broadband balun using an active circuit with negative group delay (NGD) is proposed. The unit cell of the active NGD circuit is based on a Field Effect Transistor (FET) in cascade with an RLC series network. First, a comparison between measurements of a two-stage prototype of this active topology and simulations validate the synthesis method of this innovative device. Then, thanks to the NGD circuit, a constant phase can be generated if this circuit is associated with a classical transmission line. By implementing such phase shifters into the two branches of a resistive splitter, we obtain a new balun topology. The NGD balun simulation results show a rather constant differential output phase (180degplusmn9deg), insertion losses above -2.4 dB and an excellent isolation below -59 dB for all three ports, for a bandwidth from 3.5 GHz to 5.5 GHz.

E-Field Extraction from h-Near-Field in Time-Domain by Using Pws Method

A novel technique of the electric- or E-fleld extraction from the magnetic- or H-near-fleld in time-domain is reported. This technique is based on the use of the Maxwell-Ampere relation associated to the plane wave spectrum (PWS) transform. It is useful for the E-near-fleld computations and measurements which are practically complicated in time-domain in particular, for the EMC applications. The considered EM-fleld radiation is generated by a set of electric dipoles excited by an ultra-short duration current having frequency bandwidth of about 10-GHz. The presented EM- fleld calculation technique is carried out by taking into account the evanescent wave efiects. In the flrst step, the time-dependent H-fleld data mapped in 2-D plan placed at the height z0 above the radiating devices are transposed in frequency-dependent data through the fast Fourier transform. In order to respect the near-fleld approach, the arbitrary distance z0 between the EM-fleld mapping plan and radiating source plan should be below one-sixth of the excitation signal minimal wavelength. In the second step, one applies the PWS transform to the obtained frequency-data. Then, through the Maxwell-Ampere relation, one can extract the E-fleld from the calculated PWS of the H-fleld. In the last step, the inverse fast Fourier transform of the obtained E- fleld gives the expected time-dependent results. The relevance of the proposed technique was conflrmed by considering a set of flve dipole sources placed arbitrarily in the horizontal plan equated by z = 0 and excited by a pulse current having amplitude of 50mA and half-width of about 0.6ns. As expected, by using the Hx, Hy and Hz 2-D data calculated with Matlab in the rectangular plan placed at z0 = 3mm and z0 = 5mm above the radiating source, it was demonstrated that

Similitude between the NGD function and filter gain behaviours

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

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

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.

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

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

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

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 Nortons 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.

An Open Platform for Seamless Sensor Support in Healthcare for the Internet of Things

Population aging and increasing pressure on health systems are two issues that demand solutions. Involving and empowering citizens as active managers of their health represents a desirable shift from the current culture mainly focused on treatment of disease, to one also focused on continuous health management and well-being. Current developments in technological areas such as the Internet of Things (IoT), lead to new technological solutions that can aid this shift in the healthcare sector. This study presents the design, development, implementation and evaluation of a platform called Common Recognition and Identification Platform (CRIP), a part of the CareStore project, which aims at supporting caregivers and citizens to manage health routines in a seamless way. Specifically, the CRIP offers sensor-based support for seamless identification of users and health devices. A set of initial requirements was defined with a focus on usability limitations and current sensor technologies. The CRIP was designed and implemented using several technologies that enable seamless integration and interaction of sensors and people, namely Near Field Communication and fingerprint biometrics for identification and authentication, Bluetooth for communication with health devices and web services for wider integration with other platforms. Two CRIP prototypes were implemented and evaluated in laboratory during a period of eight months. The evaluations consisted of identifying users and devices, as well as seamlessly configure and acquire vital data from the last. Also, the entire Carestore platform was deployed in a nursing home where its usability was evaluated with caregivers. The evaluations helped assess that seamless identification of users and seamless configuration and communication with health devices is feasible and can help enable the IoT on healthcare applications. Therefore, the CRIP and similar platforms could be transformed into a valuable enabling technology for secure and reliable IoT deployments on the healthcare sector.