Francisco M. Ramos

YSZ-Based Oxygen Sensors and the Use of Nanomaterials: A Review from Classical Models to Current Trends

This work reviews physicochemical models on the operation and the response of potentiometric oxygen gas sensors based on ion-conducting electrolytes. The aim for describing the electric response and some properties like response time, ionic conductivity, catalytic activity, or gas selectivity of these devices has led to the development of some models in the last decades. These models have provided information on relations between the response of the sensors, their design and fabrications process, and some morphological properties, like grain size of the electrolyte, diffusion on protective layers, or density of three-phase boundary points in the measuring electrodes. Current trends on improving catalysis, gas selectivity, and activation energy for ion conducting by using nanomaterials are described as well.

A Low Temperature Cofired Ceramic (LTCC) technology platform for heterogeneous integrated systems

A LTCC technology platform for the integration of heterogeneous electronic systems is presented. The reliability of technical processes and the RF characterization of basic structures shows a very good performance (permittivity, εr ∼ 6.1, loss tangent < 0.002) that allows the integration of complex systems based on the System in Package (SiP) concept. As a demonstrator, it has been implemented a quadrature VCO with embedded passive devices showing a 45% tuning range.

1D/2D hybrid mesh PEEC solver for the analysis of multilayer planar circuits

To minimise the number of cells required for analysing numerically a planar circuit, an hybrid meshing technique that combines 1D and 2D cells is presented in this work. Thanks to this discretization procedure of the Partial Element Equivalent Circuit (PEEC) method, the connectivity between 1D and 2D model partitions is made using an unstructured mesh. In this way, it is possible to match regions of the layout with different number of cells at their common interface. The method is applied to the simulation of finger capacitors in a multilayer low temperature co-fired ceramic technology and it is verified with experimental data.

Customizable printed inductors on LTCC substrates for RF applications

This work is aimed to demonstrate the potential of Inkjet printing combined with electroless growth to implement high performance RF inductors on standard low temperature co-fired ceramic substrates. Enhanced customization and tuning are the main advantage of this technological combination in front of standard low temperature co-fired ceramic technology. Two sets of samples have been fabricated and their equivalent inductance and quality factors as a function of frequency are compared. The obtained results are discussed and correlated with the technological parameters of the fabrication process.

Effects of shielding structures on the performance of planar inductors

The aim of this work is the study of the performance of planar inductors due to the presence of shielding structures. Equivalent inductance, quality factor and self resonance of the component are chosen as figures of merit for a fair comparison. Two experiments are proposed. In the first one, identical inductor geometries are evaluated under three different electromagnetic boundary conditions:(i) as a stand-alone device, (ii) surrounded by a guard-ring structure, and (iii) adding a ground plane connected to the guard-ring with solid through vias. In the second one, the influence of the width of the guard-ring is studied. Experimental results are compared with a fast quasi-static partial element equivalent circuit (PEEC) solver, which is embedded in a circuit simulator, that can handle all the previous shielding conditions.

Ceramic capacitive pressure sensor based on LTCC technology

This work is focused on the design and fabrication of a capacitive ceramic pressure sensor using LTCC technology. The multilayer technology helps us to tailor the thickness of the flexible membrane depending on the pressure range we are working in. In the bottom part of the substrate a entire signal conditioning electronics is located. An integrated circuit suitably chosen for this application measures the capacitance and converts it to a proportional voltage to the pressure. The present paper will deeply discuss technological details about LTCC technology applied to these devices, as well as hot aspects of the design such as planarity of the membrane, its thickness, gap between electrodes, electrodes and guard rings. Results of the devices taking into account these aspects will be also shown.