Open Access
A 3-D-printing-oriented coaxial-line filter with wide out-of-band rejection
(IEEE, 2025-06-18) Baranowski, Michal; Pons Abenza, Alejandro; Arregui Padilla, Iván; Lopetegui Beregaña, José María; Álvarez Botero, Germán Andrés; Lamecki, Adam; Gómez Laso, Miguel Ángel; Martín Iglesias, Petronilo; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Institute of Smart Cities - ISC
In this letter, a novel design for a 3-D-printed, self-supported coaxial-line X-band filter is presented. The filter is intended for Earth observation (EO) data downlink systems, where it must effectively reject signals in a wide frequency range. The filter design incorporates a 15th-order low-pass filter structure with a smooth profile, integrated with a short bandpass section with four $\lambda /4$ short-circuited stubs. The optimization of the low-pass section is attained by means of shape deformation, including the inner and outer coaxial conductors, and leads to a wide rejection band up to around 40 GHz, to suppress the third harmonic and other undesired out-of-band frequencies. A prototype was fabricated in one piece in an aluminum alloy using selective laser melting (SLM) and measured, exhibiting excellent agreement with simulations. In terms of out-of-band performance, the proposed coaxial-line filter is superior to other related state-of-the-art solutions.
Open Access
Characterization and modeling of the capacitive HBC Channel
(IEEE, 2015) Pereira, Maicon D.; Álvarez Botero, Germán Andrés; Sousa, Fernando Rangel de; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
The increasing interest in wireless body area networks has created the need for alternative communication schemes. One example of such schemes is the use of the human body as a communication medium. This technology is called human body communication (HBC), and it offers advantages over the most common radiation-based methods, which makes it an interesting alternative to implement body area networks. The aim of this paper is to identify the influence of a fixture on the HBC channel characterization, and an extended model that includes the test fixtures to explain the measured channel response is proposed. The model was tested against the channel measurement results, and a good experiment-model correlation was obtained. The results show that the test fixture has a nonnegligible influence and that an extended model, based on the physical meaning of the phenomena involved, helps to explain the channel frequency profile results and behavior.
Open Access
Assessment of performance of one-turn inductors in series configuration through a transmission-line modeling approach
(IEEE , 2024) Álvarez Botero, Germán Andrés; Moctezuma-Pascual, Eduardo; Gómez Laso, Miguel Ángel; Torres-Torres, Reydezel; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza
In this paper, transmission-line theory is applied to implement a physical model for compact one-turn inductors, which simultaneously incorporates the frequency-dependent effects introduced by the conductor skin effect and the loss originated by the coupling with the ground plane. For this purpose, S-parameter measurements are processed to extract the associated parameters, which exhibit scalability with the turn radius. This allows the model to be used for interpolation and extrapolation analyses. In this regard, the device performance is assessed for one-turn inductors in series connection, for different load impedances, and when the turn is narrowed. To validate the proposal, agreement between the model and the experimental transmission line RLGC parameters, the return loss, and the Q-factor is obtained up to 20 GHz.
Open Access
Characterization of RF-MOSFETs in common-source configuration at different source-to-bulk voltages from S-parameters
(IEEE, 2013) Zárate-Rincón, Fabián; Álvarez Botero, Germán Andrés; Torres-Torres, Reydezel; Murphy-Arteaga, Roberto S.; Decoutere, Stefaan; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
Using a new test fixture that allows us to bias the bulk terminal through an additional compensated DC probe, a two-port S-measurement-based methodology to characterize RF-MOSFETs in common-source configuration is herein presented. In addition to obtaining S-parameters at different bulk-to-source voltages using a single two-port configured test-fixture, the proposal allows the analysis of the electrical parameters of a MOSFET that are influenced by the substrate effect when the frequency rises. Physically expected results are obtained for device's model parameters, allowing to accurately reproduce S-parameters up to 20 GHz. Furthermore, extracted parameters, such as threshold voltage, are in agreement with those obtained using well-established DC methods. This method allows one to characterize a four-terminal MOSFET from two-port small-signal measurements.
Open Access
Magneto-dielectric composites characterization using resonant sensor and neural network modeling
(IEEE, 2024) Álvarez Botero, Germán Andrés; Lobato-Morales, Humberto; Hui, Katherine; Tarabay, Naji; Sánchez-Vargas, Jeu; Vélez, Camilo; Méndez-Jerónimo, Gabriela; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza
This article presents a novel way to estimate magnetodielectric composites’ complex permittivity (ε) and permeability (µ). A methodology based on artificial neural network (ANN) modeling is proposed to determine ε and µ from S-parameter measurements around 2.45 GHz, obtained using a new microstrip split ring resonator (SRR)-based resonant sensor.
Open Access
Modeling and parameter extraction of test fixtures for MOSFET on-wafer measurements up to 60 GHz
(Wiley, 2013) Álvarez Botero, Germán Andrés; Torres-Torres, Reydezel; Murphy-Arteaga, Roberto S.; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
We present a circuit model and parameter determination methodology for test fixtures used for on-wafer S-parameter measurements on CMOS devices. The model incorporates the frequency dependence of the series resistances and inductances due to the skin effect occurring in the metal pads. Physically based representations for this effect allow for excellent theory-experiment correlations for different dummy structures, as well as when de-embedding transistor measurements up to 60 GHz.
Open Access
Modeling ground-shielded integrated inductors incorporating frequency-dependent effects and considering multiple resonances
(IEEE, 2019) Valdés-Rayón, José; Torres-Torres, Reydezel; Murphy-Arteaga, Roberto S.; Álvarez Botero, Germán Andrés; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
A model for integrated spiral inductors which incorporates the physically expected frequency-dependent effects modifying the device's impedance is proposed. Moreover, it is demonstrated that the effect of resonances occurring outside the bandwidth of applicability for the device may considerably influence the performance around the peak of the Q-factor versus frequency curve. In this paper, we present the use of cascaded resonant circuits to represent the additional resonances occurring in the device to improve model accuracy up to 60 GHz.
Open Access
Analysis of the uncertainty in measurements of polymer pellets using microwave resonant sensors
(IEEE, 2024) Covarrubias-Martínez, Dania; Lobato-Morales, Humberto; Corona-Chávez, Alonso; Ramírez-Cortés, Juan Manuel; Álvarez Botero, Germán Andrés; Méndez-Jerónimo, Gabriela; Kaur Kataria, Tejinder; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Institute of Smart Cities - ISC
The analysis and evaluation of the uncertainty in microwave measurements of some polymer plastic materials in the form of small pellets is presented in this article. Two different resonant sensors, cavity and planar, operating around 2.45 GHz are used to measure the materials. The presented uncertainty analysis is based on the measured resonant parameters from the sensors and represents a statistical tool capable of generating relevant information such as an adequate number of tests, uncertainty levels, correlation coefficient, covariance matrix, and confidence ellipses, which can be highly useful in the analysis of pellet or grained materials using microwave methods, and for fast and accurate decisions involving materials evaluation. It will be shown that a number of 40 tests for each sample is adequate for a stable uncertainty, and due to the E-field distribution and interaction with the samples, the cavity sensor develops lower uncertainty in resonant frequency compared to the planar circuit, thus, it can be a more reliable sensor for polymer pellet measurements.
Open Access
Consistent modeling and power gain analysis of microwave SiGe HBTs in CE and CB configurations
(IEEE, 2015) Álvarez Botero, Germán Andrés; Torres-Torres, Reydezel; Murphy-Arteaga, Roberto S.; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
This paper presents a methodology to model SiGe HBTs biased in common-emitter and in common-base configurations including the bias-dependent substrate parasitics, which allows determining the more suitable configuration to achieve maximum power gain at different frequency ranges. Model-experiment correlations up to 100 GHz for different bias conditions verify the validity of the proposed circuit representations using the same values for the parameters in both configurations.
Open Access
Using S-parameter measurements to determine the threshold voltage, gain factor, and mobility degradation factor for microwave bulk-MOSFETs
(Elsevier, 2011) Álvarez Botero, Germán Andrés; Torres-Torres, Reydezel; Murphy-Arteaga, Roberto S.; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
In this paper, we present an extraction and characterization methodology which allows for the determination, from S-parameter measurements, of the threshold voltage, the gain factor, and the mobility degradation factor, neither requiring data regressions involving multiple devices nor DC measurements. This methodology takes into account the substrate effects occurring in MOSFETs built in bulk technology so that physically meaningful parameters can be obtained. Furthermore, an analysis of the substrate impedance is presented, showing that this parasitic component not only degrades the performance of a microwave MOSFET, but may also lead to determining unrealistic values for the model parameters when not considered during a high-frequency characterization process. Measurements were made on transistors of different lengths, the shortest being 80 nm, in the 10 MHz to 40 GHz frequency range.