Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Current cardiopulmonary activity monitoring is based on contact devices which cannot be used in extreme cases such as premature infants, burnt victims or rescue operations. In order to overcome these limitations, the use of radar... more
Current cardiopulmonary activity monitoring is based on contact devices which cannot be used in extreme cases such as premature infants, burnt victims or rescue operations. In order to overcome these limitations, the use of radar technologies emerges as an alternative. This paper aims to enhance the comprehension that non-contact technologies, in particular radar techniques, offer as a monitoring tool. For this purpose, a modified low cost commercial 122 GHz frequency-modulated continuous-wave (FMCW) radar is used to better fit the current application domain. The radar signals obtained are processed using a classic linear filtering algorithm aiming to separate the breathing from the heartbeat component while preserving signals integrity. In a standoff configuration and with different subject orientations, results show that the signal obtained with the radar can be used to extract not only the respiratory and heartbeat rates, but also the heart rate variability (HRV) sequence. Moreov...
Research Interests:
FPGAs can implement digital signal processing algorithms in a fast and efficient way. In this work we present different hardware architectures for the implementation of the Hilbert transform on FPGAs. This transform is especially useful... more
FPGAs can implement digital signal processing algorithms in a fast and efficient way. In this work we present different hardware architectures for the implementation of the Hilbert transform on FPGAs. This transform is especially useful for the generation of analytic signals that are required by many applications (digital demodulators, PLLs, electronic warfare receivers, etc.). We have explored the implementation of several structures looking for architectures that allow real time processing of high input rates with a reasonable area overhead. A new architecture that provides efficient computation has been presented. Experimental results with Xilinx FPGAs show the feasibility of the proposal.
Research Interests:
Research Interests:
Research Interests:
Research Interests:
The fully adaptive radar framework aims to use the available information from the scenario in which a system is deployed to adaptively change its configuration with the intention of achieving a performance improvement. The use of this... more
The fully adaptive radar framework aims to use the available information from the scenario in which a system is deployed to adaptively change its configuration with the intention of achieving a performance improvement. The use of this strategy relies on an optimization procedure, usually based on the minimization of the predicted conditional Cramér-Rao lower bound, which in some difficult scenarios can result in misperformance of the system due to a lack of robustness. In this paper, we present a novel approach based on a linear-Gaussian approximation, to carry out the optimization procedure inherent in the fully adaptive radar framework that successfully avoids these robustness issues. This method can be easily implemented using sigma-point integration methods. We demonstrate the performance of the proposed approach through simulations in a single target tracking scenario using a sensor network.
Research Interests:
This paper presents the analysis of mixed-phase cloud observations in Madrid (Spain) carried out with a 94-GHz ground-based CW-LFM radar system. This analysis is based on the 3D reflectivity profiles and the Doppler spectra. The case of... more
This paper presents the analysis of mixed-phase cloud observations in Madrid (Spain) carried out with a 94-GHz ground-based CW-LFM radar system. This analysis is based on the 3D reflectivity profiles and the Doppler spectra. The case of interest occurred on 29th January 2016 when a melting layer at 1 Km, up- and downdrafts and drizzle were detected. This radar can be used to estimate the microphysical composition of the detected mixed-phase clouds.
Research Interests:
We propose transmission line pulse (TLP) stress instead of DC bias stress in order to stimulate different failure mechanisms for HBTs for wafer level reliability characterisation and show the effects of degradation on the device... more
We propose transmission line pulse (TLP) stress instead of DC bias stress in order to stimulate different failure mechanisms for HBTs for wafer level reliability characterisation and show the effects of degradation on the device performance. The established Wunsch-Bell model [1] is employed for a calculation of the intrinsic device temperatures within the active region from the measured pulse voltage and current. The device MTTF can be predicted for various thermally induced failure modes. Additional degradation mechanisms related to the high current densities obtained during TLP stress show that this method is more operational than the established accelerated lifetime tests.
Research Interests:
InGaAs is an attractive material for high-speed, high-frequency electronics and ultra-low-noise applications. A great effort has taken place recently towards the development of high-performance InGaAs MOSFETs with different geometries:... more
InGaAs is an attractive material for high-speed, high-frequency electronics and ultra-low-noise applications. A great effort has taken place recently towards the development of high-performance InGaAs MOSFETs with different geometries: planar MOSFETs, FinFETs and Nanowire MOSFETs. This exploration has uncovered a number of interesting device physics of relevance to the development of electronics based on other material systems. InGaAs is a narrow bandgap material. As such, it is prone to excess band-to-band tunneling at moderate voltages. Due to the floating nature of the InGaAs MOSFET body, holes generated by BTBT cannot escape from the body. Through a parasitic lateral bipolar transistor that is hiding inside the MOSFET, this results in excess off-state current which compromises transistor logic operation. InGaAs also features a very small effective mass. This yields prominent ballistic effects in nanoscale devices. Towards studying this, we have developed a new technique to extract mobility and injection velocity in InGaAs MOSFETs in the presence of severe gate oxide trapping, as is the case in the high-k/InGaAs MOS system. In InGaAs FinFETs, we find a degradation in scattering limited mobility but an enhancement in ballistic mobility as the fin-width narrows. Also, the injection velocity shows no discernable fin width dependence. An important lesson from these studies is that long-channel mobility measurements constitute a poor predictor of short-channel performance of InGaAs FinFETs.
Research Interests:
This paper studies non linear distortion effects in two different architecutres of ultra wideband GaN power amplifiers. As transmitted power, carrier frequency and modulation complexity increase in modern communications systems, there is... more
This paper studies non linear distortion effects in two different architecutres of ultra wideband GaN power amplifiers. As transmitted power, carrier frequency and modulation complexity increase in modern communications systems, there is a need to characterize nonlinearity in HPAs. Two general purpose HPAs, designed and manufactured using European GaN technology, are analyzed in a complex modulation scenario, to characterize the effects produced by their nonlinear features.
Research Interests:
In the past decades, monostatic security screening radars in the millimeter and submillimeter wave bands have progressed into feasible threat detection prototypes. Although these systems have been proven to be successful in revealing... more
In the past decades, monostatic security screening radars in the millimeter and submillimeter wave bands have progressed into feasible threat detection prototypes. Although these systems have been proven to be successful in revealing concealed weapons in static and controlled environments, future security checkpoints demand high detection probabilities even with moving subjects. In this regard, monostatic systems can only generate images from a single viewpoint, omitting the detection of person-borne threats in nonviewed areas of the body. In addition, the vanishing and glint caused by specular reflection as the person moves through the checkpoint are still unsolved problems. In this article, a proof-of-concept implementation of a multistatic architecture to bypass these issues for a 300 GHz three-dimensional imaging radar is evaluated. The approach is based on the distribution of separated transmitters to provide enough angular diversity to maintain target detection in at least one of the resulting images. Measured results from various viewpoints are presented to show the usefulness of such a configuration with imaging scenarios of common threats.
Research Interests:
Research Interests:
The fully adaptive radar framework aims to use some known information, or cognition, about the environment in which the system is deployed to obtain some improvement in its performance, typically either reducing the uncertainty of the... more
The fully adaptive radar framework aims to use some known information, or cognition, about the environment in which the system is deployed to obtain some improvement in its performance, typically either reducing the uncertainty of the obtained results or optimizing the use of the available resources. In this paper, the extension of the fully adaptive radar framework for the case of multiple target tracking is introduced. In order to illustrate the proposed framework use, a simulation is carried out in an scenario comprising multiple targets and a sensor network with resource constraints. Results show a remarkable performance improvement when the proposed fully adaptive radar approach is used.
Research Interests:
Research Interests:
This work explores the capabilities of spectral correlation based detectors for partially or completely unknown signals corrupted by Gaussian noise. The main contribution is twofold: Firstly, the cyclostationary model is shown to be less... more
This work explores the capabilities of spectral correlation based detectors for partially or completely unknown signals corrupted by Gaussian noise. The main contribution is twofold: Firstly, the cyclostationary model is shown to be less suitable for detection purposes than the stationary model. Secondly, analytic approximations are derived for the detection and false alarm probabilities, under the assumption of long observation
Research Interests:
Research Interests:
Frequency multipliers are the current choice for the generation of local oscillator signal for submillimetre-wave receivers up to terahertz frequencies. We have investigated multiplier chains based on Schottky diodes using a numerical... more
Frequency multipliers are the current choice for the generation of local oscillator signal for submillimetre-wave receivers up to terahertz frequencies. We have investigated multiplier chains based on Schottky diodes using a numerical physical model and validated these results with measurements for Herschel instruments from Jet Propulsion Laboratory (JPL). Experimental results approach the theoretical limit of operation at frequencies below 1 THz. However, at increasing frequencies the output power drops with frequency faster than 1/f2 predicted by theory. Therefore, devices at high frequencies are operating inefficiently mainly because anode areas are not optimized at all. Proper selection of this parameter allows a big improvement in output power above 1 THz.
Research Interests:
This paper deals with the problem of tracking using a sensor network when the sensors are not synchronised. We propose a new algorithm called the asynchronous particle filter that, with much less computational burden than the traditional... more
This paper deals with the problem of tracking using a sensor network when the sensors are not synchronised. We propose a new algorithm called the asynchronous particle filter that, with much less computational burden than the traditional particle filter, has a slightly poorer performance. Thus, it is a good solution to real-time applications with non-synchronised sensors when high performance is
Research Interests:
Abstract: The optimization of Schottky diode operation together with the design of circuits based on these devices can be accomplished with a developed 2-D drift-diffusion simulator. Evaluation of the impact of different geometries on the... more
Abstract: The optimization of Schottky diode operation together with the design of circuits based on these devices can be accomplished with a developed 2-D drift-diffusion simulator. Evaluation of the impact of different geometries on the device performance and study of ...
Research Interests:
Research Interests:
Engineering, Computer Science, Millimeter Wave Antennas, Satellite Communication, IEEE, and 10 moreLow noise amplifier, Real Time, Integrated Circuit, PATCH ANTENNA, Electrical And Electronic Engineering, Global position ing system, Positioning System, Application Specific Integrated Circuit (ASIC), Millimeter Wave, and Field Test
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
ABSTRACT Thermal management has become an important issue in the design of Schottky diode-based circuits for high power applications. This work presents a physics-based numerical electro-thermal model for Schottky diodes capable of... more
ABSTRACT Thermal management has become an important issue in the design of Schottky diode-based circuits for high power applications. This work presents a physics-based numerical electro-thermal model for Schottky diodes capable of evaluating the thermal effects on the electrical performance of devices and circuits. The advantages of this model are the inclusion of temperature-dependent material parameters, the capability to calculate internal temperature distributions, and the identification of regions where heat is generated, providing useful information for device design and circuit reliability. The developed electro-thermal model is integrated into a circuit simulator in order to provide a tool which can be used to analyze, design and optimize Schottky diode-based circuits for high power operation. This tool has been validated with a 200 GHz doubler from the Jet Propulsion Laboratory (JPL-NASA). A better agreement with measurement results at high input powers is obtained with our model compared with other previous models reported in the literature due to the self-consistent implementation of the temperature-dependency of physical parameters like electron mobility and saturation velocity.
Research Interests:
ABSTRACT The evaluation of multiple target tracking algorithms with labelled sets can be done using the labelled optimal subpattern assignment (LOSPA) metric. In this paper, we provide the expression of the same metric for fixed and known... more
ABSTRACT The evaluation of multiple target tracking algorithms with labelled sets can be done using the labelled optimal subpattern assignment (LOSPA) metric. In this paper, we provide the expression of the same metric for fixed and known number of targets when vector notation is used.
Research Interests:
Research Interests:
Research Interests:
Research Interests:
ABSTRACT The problem of detecting an unknown signal embedded in white Gaussian noise is addressed. A CFAR detector based on combining the information of the whole frequency- cyclefrequency plane is proposed. An analytical characteri-... more
ABSTRACT The problem of detecting an unknown signal embedded in white Gaussian noise is addressed. A CFAR detector based on combining the information of the whole frequency- cyclefrequency plane is proposed. An analytical characteri- zation of the detector is provided, and its detection capability evaluated. The FFT-Accumulation Method (FAM) is used to measure the SCF. Approximate analytic expressions of the probability of false alarm are provided.
Research Interests:
ABSTRACT We have investigated two different strategies to improve the quality of ISAR images corrupted by Gaussian noise. The images are generated using a Time Frequency technique known as Atomic Decomposition (AD). The first strategy is... more
ABSTRACT We have investigated two different strategies to improve the quality of ISAR images corrupted by Gaussian noise. The images are generated using a Time Frequency technique known as Atomic Decomposition (AD). The first strategy is a classical denoising ...
ABSTRACT A fast algorithm to approximate the first two moments of the posterior probability density function (pdf) in nonlinear non-Gaussian Bayesian filtering is proposed. If the pdf of the measurement noise has a bounded support and the... more
ABSTRACT A fast algorithm to approximate the first two moments of the posterior probability density function (pdf) in nonlinear non-Gaussian Bayesian filtering is proposed. If the pdf of the measurement noise has a bounded support and the measurement function is continuous and bljective, we can use a modified prior pdf that meets Bayes' rule exactly. The central idea of this paper is that a Kalman filter applied to a modified prior distribution can improve the estimate given by the conventional Kalman filter. In practice, bounded support is not required and the modification of the prior is accounted for by adding an extra-point to the set of sigma-points used by the unscented Kalman filter.
Research Interests:
This paper presents a modification of a linear frequency modulation-continuous waveform shipborne surveillance radar (Perez et al. (2002)) with two antennas to transform it into airport surface detection equipment with a single antenna.... more
This paper presents a modification of a linear frequency modulation-continuous waveform shipborne surveillance radar (Perez et al. (2002)) with two antennas to transform it into airport surface detection equipment with a single antenna. The most important additional subsystem for this new equipment is a reflected power canceller to overcome the problem of insufficient isolation between the transmitter and receiver due