J.R. Sendra

All-optical phase modulation for integrated interferometric biosensors

We present the theoretical and the experimental implementation of an all-optical phase modulation system in integrated Mach-Zehnder Interferometers to solve the drawbacks related to the periodic nature of the interferometric signal. Sensor phase is tuned by modulating the emission wavelength of low-cost commercial laser diodes by changing their output power. FFT deconvolution of the signal allows for direct phase readout, immune to sensitivity variations and to light intensity fluctuations. This simple phase modulation scheme increases the signal-to-noise ratio of the measurements in one order of magnitude, rendering in a sensor with a detection limit of 1.9·10⁻⁷ RIU. The viability of the all-optical modulation approach is demonstrated with an immunoassay detection as a biosensing proof of concept.

Integrated inductors modeling and tools for automatic selection and layout generation

In this work we propose new equivalent circuit models for integrated inductors based on the conventional lumped element model. Automatic tools to assist the designers in selecting and automatically laying-out integrated inductors are also reported. Model development is based on measurements taken from more than 100 integrated spiral inductors designed and fabricated in a standard silicon process. We demonstrate the capacity of the proposed models to accurately predict the integrated inductor behavior in a wider frequency range than the conventional model. Our equations are coded in a set of tools that requests the desired inductance value at a determined frequency and gives back the geometry of the better inductors available in a particular technology.

PN junction integrated varactors for RF applications at different standard frequencies

In this work, new structures based on the PN junction are presented for the design of integrated varactors. In order to optimize the ratio capacitance per unit area (C/A), two varactor geometries have been developed: interdigitated and cross structures. Varactors have been characterized with a specific measurement methodology. A library of varactors that can be used in different RF applications has been implemented with good quality factors and a tuning range around 30%.

Integrated Inductors Modeling for Library Development and Layout Generation

In this work we propose a modification to the conventional lumped equivalent circuit model for integrated inductors. Also the widely used parametric model is modified. The proposed models expand the frequency range where the integrated inductor behavior is accurately predicted. They are useful in developing automatic tools to assist the designers in selecting and automatically laying-out integrated inductors [1]. This work is based on measurements from integrated inductors fabricated in a standard silicon process.

A novel geometry for circular series connected multilevel inductors for CMOS RF integrated circuits

The scope of this brief is to introduce a novel geometry for circular series connected multilevel inductors. The idea is to improve the overlapping of the different metal layers that form the integrated inductor to maximize the magnetic flux shared by them and so the inductance. The performance of this new geometry has been compared with the conventional one, using Agilent HFSS field solver. After that, two multilevel inductors using this new geometry have been fabricated in a standard 0.6 /spl mu/m three-metal CMOS process and measured.

Configurable Quadrant Photodetector: An Improved Position Sensitive Device

Position sensitive detectors (PSDs), used in high-end biotechnology, are based on optical sensors built over quadrant photodetectors (QPDs) or active pixel sensor (APS). These devices are intended to measure slight movements of laser spots. The QPD are, by far, the best approach in terms of resolution and noise, but requires complex and expensive x-y micropositioners to perform sensor alignment with the incoming laser spot. The APSs are more versatile devices that can virtually align with the spot by means of device configuration. However, due to its intrisic digital nature, the SNR and the resolutions are degraded in APS. In this paper, a new type of device called configurable QPD and its theory of operation is presented. This new device combines the analog operation of the QPD with the configurability of the APS, by means of combining photodetectors elements with analog switches in a matrix-shaped architecture. Finally, a prototype chip has been fabricated and tested and its measurements results are presented.

Models and Tools for CMOS Integrated Inductors

In this paper we are reporting our research in the development of automatic tools to assist the designers in selecting and automatically laying-out integrated inductors. This task is accomplished by analyzing carefully the lumped equivalent circuit model for these passive components, and using different approaches and modifications depending on the required accuracy and application. As a result modified circuit models for integrated inductors based on the conventional lumped element model are proposed. Model development is based on measurements taken from more than 100 integrated spiral inductors designed and fabricated in a standard silicon process. We show the ability of the proposed models to accurately predict the integrated inductor behavior extending the frequency range where they can be applied as compared with the conventional model.

Characterization of extrinsic resistances in temperature behaviour modelling of InGaAs MODFETs

This work analyses the dc response of InGaAs channel modulation-doped field-effect transistors, when varying temperature from 300 to 400 K. An analytical model for the intrinsic drain current is derived from previous work, carried out for a similar AlGaAs channel device, in order to show explicitly the temperature dependence. The extrinsic resistances are numerically evaluated and added in a straightforward form to the model. Experimental output characteristics at different temperatures of an InGaAs MODFET, in static operation, are compared with those offered by the resulting extrinsic model and numerical simulations. Computed relative errors are around 10%.

Development of a surface plasmon resonance and nanomechanical biosensing hybrid platform for multiparametric reading

We have developed a hybrid platform that combines two well-known biosensing technologies based on quite different transducer principles: surface plasmon resonance and nanomechanical sensing. The new system allows the simultaneous and real-time detection of two independent parameters, refractive index change (Δn), and surface stress change (Δσ) when a biomolecular interaction takes place. Both parameters have a direct relation with the mass coverage of the sensor surface. The core of the platform is a common fluid cell, where the solution arrives to both sensor areas at the same time and under the same conditions (temperature, velocity, diffusion, etc.).The main objective of this integration is to achieve a better understanding of the physical behaviour of the transducers during sensing, increasing the information obtained in real time in one single experiment. The potential of the hybrid platform is demonstrated by the detection of DNA hybridization.

On silicon integrated inductor library design for wireless applications

This contribution reports our research in developing an integrated inductor library. From a tutorial perspective the main limitations of this element, when grown on standard silicon technologies, are presented, offering measured results taken from a set of fabricated inductors and design guidelines to improve their performance. The modeling aspects are also covered, we present results for different equivalent lumped circuits and parameter extraction styles. From the designers point of view, we state the main characteristics that a good integrated inductor library should include. We also report our proposed solution for this task consisting in a set of tools to automate the element selection such as their laying-out. This library development procedure and the associated tools cover the lack of these elements in present offered design kits.