Showing papers by "Blaise Ravelo published in 2018"

The Design Method of the Active Negative Group Delay Circuits Based on a Microwave Amplifier and an RL-Series Network

Abstract: This paper addresses a circuit theory regarding the negative group delay (NGD) principle. The methodology for characterizing this unfamiliar NGD function is described. The basic NGD topology under study is typically an active cell composed of an RF low-noise amplifier (LNA) and an RL-series passive network. It acts as a low-pass NGD topology. The family of the bandpass NGD cell is identified from the low-pass to the bandpass transform. The NGD circuit theory under study is essentially built with the S-parameter approach. The main characteristics of the proposed NGD topology and properties of the NGD level, cut-off frequencies or bandwidth, central frequency, and figure-of-merit are established. The NGD cell is synthesized using the LNA S-parameter model. A method for designing the low- and bandpass NGD cells as a function of the specified NGD values is presented. The NGD cell parameter calculations as functions of the expected NGD level, insertion loss, and reflection coefficient are introduced. Proof-of-concept NGDs are synthesized, designed, simulated, and fabricated to understand and validate the proposed NGD low-pass and bandpass functions. As expected, low-pass and bandpass NGD aspects are obtained. The low-pass NGD circuits present an NGD level of approximately −5 ns over the bandwidth fc = 25 MHz. Next, bandpass NGD circuits were synthesized to operate at approximately 0.5 GHz over the bandwidth $\Delta \text{f}\,\,=50$ MHz with an NGD level of approximately −10 ns. The measured results of the low-pass and bandpass NGD are in good agreement with the theoretical prediction obtained with simple lumped circuits. Different applications of the unfamiliar NGD function are described.

S-Parameter Model of Three Parallel Interconnect Lines Generating Negative Group-Delay Effect

Abstract: This paper develops a negative group-delay (NGD) microwave circuit theory regarding topology consists of three parallel interconnect lines (3-PILs). The NGD topology under study is built using completely distributed microstrip lines. The 3-PIL NGD theory is established from the S-parameters which are determined from the general admittance matrix of the 3-PILs. The analytical expressions of reflection coefficient (S11), transmission coefficient (S21) and group-delay ( $\tau$ ) which behave as periodical functions are presented. The frequency period proper to the 3-PIL topology is established. Then, S11, S21 and $\tau $ illustrating the possibility to generate bandpass NGD function are formulated in function of the PIL parameter physical lengths and attenuation loss. Then, the NGD characterization of the 3-PIL topology is presented. The relevance of the NGD theory is verified with simulations and experimentations around the NGD center frequency of about 2.3 GHz. To do this, a 3-PIL microstrip circuit is designed and fabricated as proof-of-concept. It is shown that the simulated and measured group-delays are well-correlated. As expected theoretically, the demonstrator with identical characteristic impedance enables to generate an NGD level of approximately −2 ns at 2.3 GHz. In the future, the NGD function can be potentially used for the microwave signal integrity improvement.

X-band negative group-delay lossy stub line

Abstract: This study investigates the negative group delay (NGD) passive circuit constituted by a fully distributed parallel stub line. The proposed S-parameter modelling is developed. The transmission parameter band-pass NGD function identification is described. The NGD characterisation is established by determination of the NGD level and bandwidth in function of the stub line parameters. It was analytically found that with a basic cell consisted of single stub line, the insertion loss is usually degraded to reach significant figure-of-merit which is obtained with the NGD level-bandwidth product. As a solution, it is shown that this insertion loss can be improved with the consideration of matching network. As proof-of-concept (POC), microstrip distributed circuits printed on the flexible Kapton substrate without lumped element were synthesised, designed and fabricated. The theoretical, simulated and measured results are in good correlation. As expected, band-pass NGD behaviours centred beyond 10 GHz were observed. The POC generates NGD level of about -1.5 ns over the NGD bandwidth 0.65 GHz. In the future, thanks to the theoretical approach simplicity and the topology integrability, the NGD principle can be potentially useful for the improvement of RF/microwave circuits.

Direct Time-Domain TAN Model of 3D Multilayer Hybrid PCB: Experimental Validation

Abstract: The multilayer technology constitutes the ultimate solution for the design of high-density printed circuit board (PCB). Challenging modeling method is required to predict the signal integrity (SI) of the multilayer PCB. This paper addresses an unfamiliar direct time-domain model of a 3-D multilayer hybrid PCB. The subnetwork primitive elements of the equivalent graph are constituted by lumped components, interconnect lines, vias, pads, and anti-pads. The tensorial analysis of networks (TANs) is used to solve the problem related to the graph topology in the function of the PCB design parameters. The TAN concept is based on the interaction between the primitive elements. The mesh currents constitute the proposed computational unknowns. The unfamiliar model is validated with a three-port network prototype constituted by the six-layer PCB, including passive SMD components. In the frequency domain, S-parameter validation from 100 kHz to 5 GHz is presented. By using 80-Mb/s and 0.5-Gb/s rate data patterns, the proposed TAN model is validated by both simulations and measurements in the time domain. The transient results present vector magnitude relative error accuracy lower than 15%. Thanks to the computation speed and adaptability to multilayer hybrid structures, the TAN model is a prominent approach for the SI and power integrity analyses of 3-D multilayer structures.

Theory on negative time-delay looped system

Abstract: An innovative theory on the looped system generating negative time delay is presented. Both the direct and delayed feedback loop topologies of this system essentially consist of an independent-frequency gain and time-delay block. It is shown theoretically that for suitable parameters the system can generate a negative time delay by virtue of a negative group delay (NGD). Analytical expressions reveal that the system presents an unconditional low-pass NGD behaviour. The NGD properties as a function of the system parameters are derived. To demonstrate the feasibility of the developed NGD system concept, frequency- and time-domain analyses are performed with Matlab, resulting in a very good agreement between the simulations and theory. Furthermore, as illustrated by computational results, negative time-delay signal propagation (signal advance) is obtained. The proposed NGD system can potentially be useful for time-delay compensation in engineering systems.

PCB access impedances extraction method of in-situ integrated circuit

Abstract: This article describes an extraction technique of input and output impedances of integrated circuits (ICs) implemented onto the printed circuit boards (PCBs). The feasibility of the technique is illustrated with a proof-of-concept (POC) constituted by two ICs operating in a typically transmitter-receiver (Tx-Rx) circuit. The POC system is assumed composed of three different blocks of emitter signal source, load and interconnect passive network. This latter one is assumed defined by its chain matrix known from its electrical and physical characteristics. The proposed impedance extraction method is elaborated from the given signals at the transmitter output and receiver input. The terminal access impedances are formulated in function of the parameters of the interconnect system chain matrix. The feasibility of the method is checked with a passive circuit constituted by transmission lines driven by voltage source with RL-series network internal impedance and loaded at the output by the RC-parallel network. Good correlation between the access impedance reference and calculated is found.

Resistive Active Balanced Power Divider Design with Touchstone and Kron’s Formalism Hybrid Model

Abstract: A resistive active power divider (RAPWD) design based on Kron’s model is introduced. The threeway RAPWD topology is essentially constructed with a low noise amplifier (LNA) with input and output matching shunt resistances. The RAPWD S-parameter is analytically expressed from the Kron’s method hybridized with the LNA touchstone model. The RAPWD synthesis relation is established in function of the expected gain and matching access. The feasibility of the established Kron’s method modelling is validated with a proof-ofconcept (POC) using the surface mounted monolithic LNA LEE-9+ from mini-circuits. As expected, S-parameters are in good correlation between simulations and computed results from the proposed hybrid method. A relatively flat transmission gain of about 9+/-0.2 dB is realized in the very wide frequency band 0.5 to 4.5 GHz. The broadband tested RAPWD input and output matching and access port isolations are widely better than 10 dB.

1:4 Tree microstrip interconnect Kron-Branin model

Abstract: An uncommon computational model of printed circuit board (PCB) interconnect tree is developed. The proposed model is based on the Kron-Branin (KB) formalism. This uncommon KB method consists in traducing the tree interconnect network into a graph structure. The graph topology is constituted by the branches, nodes and coupling cords. The mathematical abstraction of the graph enables to establish the KB characteristic of the problem represented by the tree interconnect system. After the branch current calculations, the S-parameter model is established. The uncommon KB model is validated with a prototype of single-input and four-outputs (1:4) microstrip interconnect tree. As expected, the calculated S-parameters from the KB model are in good agreement with simulations and measurements from DC to 4 GHz. Thanks to the computation speed and accuracy, the KB model is prominent for the fast computation of interconnect structures and useful for the PCB EMC and signal integrity analyses.

Unity direct chain with feedback series impedance based innovative negative group delay circuit

Abstract: An innovative negative group delay (NGD) circuit theory on unity direct chain (UDC) topology is developed in this paper. The NGD UDC cells are based on the operational amplifier adder with feedback series impedance. Innovative topologies of high-pass NGD UDC cell composed of RL-series network, all-pass RC-parallel network and low-pass RC-series network are identified. It is a first time that all-pass NGD original topologies are defined. NGD analyses and synthesis methods of each NGD UDC cells are provided. The UDC cell based NGD functions are validated with SPICE simulations. The proofs-of-concept (POC) of UDCs behave as all-pass and low-pass NGD functions with group delay equal to −1 ms at very low frequencies. The low-pass NGD cut-off frequency is 424 Hz. The high pass NGD circuit generates −1 µs at the optimal NGD frequency of about 5.15 kHz. Further analysis of the operational amplifier gain and bandwidth effects is performed. The operational amplifier gain affects significantly the NGD level and bandwidth for the all considered UDC cells. Nevertheless, only the RC-parallel feedback based UDC cell is particularly sensitive to the operational bandwidth.

Kron–Branin modelling of ultra-short pulsed signal microelectrode

Abstract: An uncommon circuit modelling of microelectrode for ultra-short signal propagation is developed. The proposed model is based on the Tensorial Analysis of Network (TAN) using the Kron–Branin (KB) formalism. The systemic graph topology equivalent to the considered structure problem is established by assuming as unknown variables the branch currents. The TAN mathematical solution is determined after the KB characteristic matrix identification. The TAN can integrate various structure physical parameters. As proof of concept, via hole ended microelectrodes implemented on Kapton substrate were designed, fabricated and tested. The 0.1-MHz-to-6-GHz S-parameter KB model, simulation and measurement are in good agreement. In addition, time-domain analyses with nanosecond duration pulse signals were carried out to predict the microelectrode signal integrity. The modelled microstrip electrode is usually integrated in the atom probe tomography. The proposed unfamiliar KB method is particularly beneficial with respect to the computation speed and adaptability to various structures.

Temperature Effect Kron-Branin Model of Tree Microstrip Interconnects

Abstract: This paper introduces an unfamiliar modelling of single-input four-output (1:4) tree microstrip interconnect with ambient temperature effect. The modelling concept is based on the Kron-Branin (KB) formalism which is elaborated with the tree interconnect graph topology. Then, the problem metric taking into account the temperature effect is established based on the tensorial analysis of network (TAN). The analytical solution is presented as the tree network S-parameters. The proposed KB modelling concept feasibility is validated by measurement with a microstrip prototype. The prototype structure is designed based on two-layer microstrip printed circuit board with based Kapton substrate. The modelled S-parameters from 100 kHz to 8.5 GHz are rather in good agreement with the experimental results with temperature variation from 30°C to 130°C. The proposed model can be useful for predicting the PCB signal integrity taking into account the ambient temperature.