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Showing papers by "Blaise Ravelo published in 2016"


Journal ArticleDOI
TL;DR: In this article, a fundamental theory of coupled line coupler-based negative group delay (NGD) topology is established, which consists of the isolated-and coupled-accesses connected in a feedback loop through a lossy interconnect line.
Abstract: A fundamental theory of coupled line coupler-based negative group delay (NGD) topology is established in this paper. The microwave circuit under study consists of the isolated-and coupled-accesses connected in a feedback loop through a lossy interconnect line. The NGD topology is built with fully distributed elements. The S-parameter model is formulated in order to derive the NGD optimal values, cutoff frequencies, and bandwidth. Thus, the NGD existence condition as a function of the coupling coefficient and the feedback interconnection attenuation is demonstrated and examined. Hence, the fundamental characteristics of the coupler-based NGD topology are described. In order to verify the feasibility of the theory, NGD prototypes were designed, fabricated, and measured. The implemented one- and two-stage microstrip circuits have NGDs of about −2.3 and −4 ns, respectively, at 1.26 GHz. The reflection coefficients are better than 10 dB and the insertion losses are, respectively, about 2.4 and 4.3 dB. The developed NGD topology, fully constructed with distributed elements without any lumped components, is particularly beneficial in terms of design simplicity. The proposed NGD circuit might find potential application in microwave signal delay correction.

68 citations


Journal ArticleDOI
TL;DR: In this paper, the authors proposed a correction technique based on the use of the negative group delay (NGD) circuits, which can compensate the signal delay in baseband frequency up to hundreds MHz with low-pass NGD circuit and 2.45 GHz modulated microwave signals with band-pass ND circuit.
Abstract: With the increase of the electrical interconnect network complexity, the signal integrity (SI) analysis becomes crucial for the electronic RF and mixed circuit designer. Approximated and optimized models of printed circuit boards (PCBs) electrical interconnect network were developed. However, interconnect effect correction techniques are still needed. The present paper addresses an example of correction technique of electrical interconnect for the PCBs. The feasibility of the concept is verified by considering a distributed transmission line (TL) latency and delay correction. The proposed correction technique is based on the use of the negative group delay (NGD) circuits. The theoretical approach including the NGD cell synthesis relations are established. The innovative low- and band-pass NGD topologies are suggested respectively for the baseband and modulated signal delay reduction. The fundamental characteristics of the low- and band-pass NGD cells are examined. The proposed technique is applied to the compensation of the microstrip interconnect line delay. It was found that the NGD effects enable to compensate the signal delay in baseband frequency up to hundreds MHz with low-pass NGD circuit and 2.45 GHz modulated microwave signals with band-pass NGD circuit. In both cases, the possibilities to reduce the latency and delay of some nanoseconds (ns) are performed.

39 citations


Journal ArticleDOI
08 Dec 2016-Sensors
TL;DR: 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 are presented.
Abstract: 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.

37 citations


Journal ArticleDOI
TL;DR: In this paper, indium doped nano sized nickel zinc cobalt based ferrite ceramics with composition Ni 0.5 Zn 0.3 Co 0.4 Fe 1.6 O 4 were synthesized by a co-precipitation technique.

29 citations


Journal ArticleDOI
TL;DR: In this paper, an original theory on negative group-delay (NGD) topology of parallel interconnect line (PIL) was described, which consists of a fully distributed circuit without lossy lumped components.
Abstract: This paper describes an original theory on negative group-delay (NGD) topology of parallel interconnect line (PIL). The proposed topology consists of a fully distributed circuit without lossy lumped components. The PIL voltage transfer function (VTF) is derived from the equivalent transfer matrix. Then, the frequency-dependent expressions of the PIL VTF gain and group delay are extracted. It is shown that the NGD phenomenon can be generated when the PIL is lossy and presenting different electrical lengths. The fundamental NGD properties versus the PIL parameters are established. This NGD concept was validated with implemented two microstrip PIL circuits. The theoretical and measured group-delay behaviors are well correlated. As expected theoretically, the demonstrator with identical 50-Ω characteristic impedance enables to generate NGD of about −4 ns at 1.75 GHz under −5-dB attenuation. Similarly, an −2.1-ns NGD level at 1.99 GHz was occurred with the other 50 Ω/117 Ω characteristic impedances NGD circuit under only −2.5-dB attenuation loss. The NGD function can be potentially used for the microwave signal integrity improvement.

26 citations


Journal ArticleDOI
TL;DR: The theoretical formulation proves that the distributed passive circuit is capable of generating the negative group delay (NGD) phenomenon and can be integrated and is useful for the microwave signal delay improvements.
Abstract: The signal delay is one of the main issues encountered during the design and fabrication of the RF/microwave electronic circuits and systems. Therefore, the correction process is constantly needed for the signal delay cancelation. This brief introduces an innovative theory of a microwave circuit topology delay suppressor. The original circuit was originally built with a passive power combiner (PWC) in feedback with an interconnect transmission line (TL) without the use of lossy lumped elements. The theoretical formulation proves that the distributed passive circuit is capable of generating the negative group delay (NGD) phenomenon. The synthesis relations enabling us to determine the circuit parameters in function of the desired NGD value are established. The innovative NGD circuit properties are elaborated. The NGD concept validation was verified with the design of fully distributed passive NGD cell built with a Wilkinson PWC in feedback with a lossy transmission line. The influence of the feedback line attenuation on the NGD function and S-parameters is discussed. A multiband NGD of about -0.7 ns was exhibited over the frequency band of about 0.12 GHz. This distributed NGD topology can be integrated and is useful for the microwave signal delay improvements.

20 citations


Journal ArticleDOI
TL;DR: In this paper, a flexible microstrip antenna 1:2 array with T-power divider (T-PWD) was designed to operate at about 58 GHz and the feasibility of the flexible antenna passive system was investigated with the proof-of-concept (POC) designed on Kapton substrate.
Abstract: Recently, the RF/microwave electronic technology evolved with the consideration of plastic and organic substrates Such a technology offers two-folded benefits: in one side for lowering the fabrication cost and in another side for the possibility to bend electronic devices Such a technology is particularly interesting for the implementation of antenna system This paper is dealing with the design of flexible microstrip antenna 1:2 array Theoretical approach on the typically symmetrical antenna 1:2 array is proposed The design methodology of microstrip antenna combined with 1:2 T-power divider (T-PWD) is described Based on the transmission line theory, the S-parameter model of the antenna system with non-standard reference load is established Then, the microstrip antenna passive system is theoretical analysed in function of the physical dimensions of the designed structure The feasibility of the flexible antenna passive system is investigated with the proof-of-concept (POC) designed on Kapton substrate The POC prototype consisted of microstrip antenna 1:2 array is designed to operate at about 58 GHz Comparisons between the full wave simulated and measured return losses were performed Then, simulated radiation pattern highlights the efficiency of the fabricated prototype of passive antenna array

19 citations


Journal ArticleDOI
TL;DR: A magnetic dipole array based time-domain modeling of electromagnetic near-field (NF) radiated by printed circuit boards (PCB) is introduced, showing the advantage of the latter.
Abstract: A magnetic dipole array based time-domain (TD) modeling of electromagnetic near-field (NF) radiated by printed circuit boards (PCB) is introduced. The behavioral equivalent model of radiated emission using elementary magnetic dipoles compliments the previously described TD model using electric dipoles. The equivalent dipole model parameters are determined by the matrix inversion method from the time-dependent magnetic NF data. The proposed modeling approach was implemented in MATLAB. As a proof of concept, the TD magnetic NF radiated by a passive microstrip test PCB exited by a nanosecond-duration signal was considered. The modeled-magnetic NF maps were compared with the reference data in the observation planes situated at some centimeters above the tested PCB, showing good agreement. The comparison between magnetic and electric dipole models was performed, showing the advantage of the latter.

17 citations


Journal ArticleDOI
TL;DR: The analytical Z -matrix equivalent to the assumed multi-port system is fundamentally established from the transmission line Kron–Branin topology, and the equivalent S-parameters of the two-level Y-tree system are established.
Abstract: This research work presents an innovative tensorial analysis of network (TAN) model of asymmetrical 1:2 Y-tree interconnects. The modelling methodology is built with Kron–Branin formalism. The analytical Z -matrix equivalent to the assumed multi-port system is fundamentally established from the transmission line Kron–Branin topology. Then, the equivalent S-parameters of the two-level Y-tree system are established. The developed model is validated with S-parameter simulations of microstrip Y-tree interconnects structure from DC to 8 GHz.

15 citations


Journal ArticleDOI
TL;DR: In this article, a flexible switching 1 × 2 antenna array with a key element RF switch terminated by two identical patch antennas associated to half-wave elementary transmission lines (TLs) is described.
Abstract: Flexible front- and back-end RF/analogue system antennas were recently emerged. However, little flexible antenna system design is available so far, in planar hybrid technology with surface mounted components. This paper describes the design feasibility of flexible switching 1 × 2 antenna array system. It acts as a switching antenna implemented in hexapole configuration. The system is comprised of a key element RF switch terminated by two identical patch antennas associated to half-wave elementary transmission lines (TLs). A detailed theory illustrating the global S-parameter model determination in function of the given RF-switch return and insertion losses is established. In difference to the conventional microwave circuit theory, the proposed equivalent S-parameter model is originally built with the non-standard optimized antenna load. Thus, the synthesis method of the terminal antenna input impedance and the output access line characteristic impedance is formulated in function of the specified return and optimal transmission losses. The design method and theoretical approach feasibility is verified with the demonstrator of flexible switching 1 × 2 antenna array printed on Kapton substrate. The circuit prototype is implemented in hybrid planar technology integrating patch antenna operating at about 6 GHz and a packaged GaAs RF switch associated to the RF/DC signal decoupling accessory mounted surface components. Simulations of the designed circuit transmission and isolation losses from 5.5 GHz to 7 GHz were carried out by using the commercial RF switch S-parameter touchstone model provided by the manufacturer. The simulated and measured return losses are compared and discussed. Then, the measured radiation patterns confirm the proposed switched antenna concept feasibility.

9 citations


Journal ArticleDOI
01 Mar 2016
TL;DR: A signal integrity analysis of high voltage rectangular short pulses for the atom-probe system is explored in this article, where the operated RF transient pulse is considered for exciting on material sample inside an ultra high vacuum (UHV) cryogenic chamber.
Abstract: A signal integrity (SI) analysis of high voltage rectangular short pulses for the atom- probe system is explored in this paper. The operated RF transient pulse is considered for exciting on material sample inside an ultra-high vacuum (UHV) cryogenic chamber. The ns- duration pulse signal is injected into the cryogenic analysis chamber through the transmitting system mainly constituted by a microstrip interconnect line ended by optical controlled nonlinear load. The whole system frequency characterization is performed based on the S- parameter measurements. As expected, a challenging ultra-short rectangular shape pulse is exhibited by the pulser. Promising experimental results with the improvement of ion mass spectrum is demonstrated with the designed RF pulser.

Proceedings ArticleDOI
24 May 2016
TL;DR: In this article, the effective relative permittivity and effective relative permeability of magneto-dielectric materials when used as substrate for microstrip antenna is analyzed through simulation and verified by synthesizing nano composite ferrite.
Abstract: The effective relative permittivity and effective relative permeability of magneto-dielectric materials when used as substrate for microstrip antenna shows interdependency. This dependency was analyzed through simulation and verified by synthesizing nano composite ferrite. The 40nm nano crystallite size particles were synthesized using a co- precipitation method. Matching values of complex permittivity (e* = 4.2-0.1j) and complex permeability (μ* = 4.3-0.2j) at 1 GHz were obtained from the electromagnetic characterization. The microstrip antenna with coaxial feed was fabricated and the interdependence of relative permittivity and relative permeability was verified. An error of 7% in the drawn length was observed for er and μr of the order of 4. The magneto-dielectric material with composition Mn0.5Zn0.3Co0.2Fe2O4+BaFe12O19 proposed in this paper definitely can be proposed as a substrate material for miniaturized antenna. The antenna with desired resonant frequency can be fabricated by calculating the effe...


Journal ArticleDOI
01 Mar 2016
TL;DR: In this article, the synthesis and sensitivity analysis of an active power splitter (PWS) is proposed based on the active cell composed of a Field Effect Transistor in cascade with shunted resistor at the input and the output (resistive amplifier topology).
Abstract: In this paper, the synthesis and sensitivity analysis of an active power splitter (PWS) is proposed. It is based on the active cell composed of a Field Effect Transistor in cascade with shunted resistor at the input and the output (resistive amplifier topology). The PWS uncertainty versus resistance tolerances is suggested by using stochastic method. Furthermore, with the proposed topology, we can control easily the device gain while varying a resistance. This provides useful tool to analyse the statistical sensitivity of the system in uncertain environment.

Proceedings ArticleDOI
01 Aug 2016
TL;DR: In this article, an empirical analysis of the thermal influence on the electrical behavior of a flexible passive patch antenna which is printed on a Kapton-based substrate is presented, and the experimental setup for measuring the input reflection coefficient with temperature variation ranging from 25°C to 150°C is described.
Abstract: This paper proposes an empirical analysis of the thermal influence on the electrical behavior of a flexible passive patch antenna which is printed on a Kapton-based substrate. The measurement protocol along with the use of the thermal chamber enabling the temperature control is presented. The experimental setup for measuring the input reflection coefficient with temperature variation ranging from 25°C to 150°C is described. Then, the input impedance of the tested microstrip circuit is analyzed given the quality factor and the antenna bandwidth. It is seen that, increasing the temperature decreases the quality factor of the antenna which is also noticeable through the matching level of the reflection coefficient. This is mainly explained by the drop of the conductivity of the top conductor made by silver ink-jet printing.