Elías de los Reyes

On the application of singular value decomposition and Tikhonov regularization to ill-posed problems in hyperbolic passive location

Abstract Hyperbolic passive location of targets (e.g. used in the Multilateration systems for civil aviation) calls for the solution of highly non-linear systems. In this paper, we show how the effect of typical ill-conditioning of passive location, arising in many operational conditions, may be significantly mitigated by regularization techniques. The pertaining advantages with respect to the conventional (non-regularized) approach are shown in a realistic situation.

Microwave Disinfestation of Bulk Timber

In this paper a complete microwave system for bulk timber disinfestation is developed and tested. A commercial FEM simulator has been used to design the applicator, looking for structures providing uniform field distributions, which is a factor of capital relevance for a successful treatment. Special attention has also been given to the reduction of electromagnetic energy leakage. A dual polarized cylindrical applicator with a corrugated flange has been designed. The applicator has also been numerically tested emulating some real-life operating conditions. A prototype has been built using two low-cost magnetrons of900 W and high power coaxial cables and it has been tested inside a shielded semianechoic chamber. The tests have been carried out in three stages: validation of the applicator design, determination of the lethal dosage as a function of the insect position and the maximum wood temperature allowed and statement of safe operation procedures.

MONITORING THE DESALTING PROCESS OF COD USING DIELECTRIC SPECTROSCOPY

The desalted cod industry needs a suitable and reliable control system to check the desalting point of cod in order to provide a safe and high-quality product. The growth of the industries that are interested in a non-contacting, real-time control, encourages the development of new methods based on low-power radiation, such as dielectric spectroscopy. These techniques use the modification of wave parameters at some specific frequencies to provide information of the compositional characteristics of foods. In this work, cod parallelepipeds were desalted at 5 °C by immersing them in distilled water for different desalting times (15 and 30 minutes and 1, 2, 4, 6, 8, 12, 24 and 48 hours). Dielectric Spectroscopy studies have been performed on cod samples in the frequency range 200 MHz-20 GHz. The dielectric properties were measured using a coaxial probe (Agilent 85070E) connected to a Network Analyzer (Agilent E8362B) immediately after removing the cod samples from their desalting solutions. After desalting, the cod samples were separated from their desalting solutions and kept in repose for 24 h at 5 °C after which some of their physical properties were measured. This experimental procedure ensures that those properties have already reached their final values. Good correlations were found between the quality properties of the cod samples (aw, xw, zNaCi and xNaC) after 24 h and their loss factor (e’) measured at 10 GHz just before leaving them in repose, showing the feasibility of an in-line control system for cod desalting process at that frequency.

Design Guidelines for Applicators Used in the Microwave Heating of High Losses Materials

Multiple port travelling wave applicators and distribution networks are tested for improved microwave heating of materials with high dielectric loss factors, based on simulation using a commercial code, ANSYS 5.6. Single point feed applicators, phase shifted by a distribution network appear to be superior over multiple feeding point applicators.

Novel Adjustable Microstrip Devices for Microwave Power Division and Impedance Matching

Abstract This paper describes the design and implementation of novel adjustable microstrip devices which made possible new methods for phase shifting, variable power division and adjustable impedance matching in the 2.45 GHz ISM band. This novel technology is more affordable and simpler to develop than other state of the art technologies described in this paper. The development of this technology took place in the frame of a degree project on energetic applications of microwaves for Microbiotech SL (MBT). These devices have been used for the proper power delivery of microwave energy to a sample material provided by Microbiotech SL. The presence of this material can modify the impedance of the applicator according to the relative permittivity of the sample and therefore reduce the amount of microwave energy delivered by the applicator to the medium. The adjustable impedance matching network made possible the total transfer of electromagnetic energy, providing a simple and versatile method for reducing return losses to a minimum regardless of the load presented to the transmission line. In the other hand, the variable power divider addressed a more common problem in microwave heating such as power flow control. It supposes an affordable approach, which may be useful in some researching scenarios. The mechanism is based on the sliding of microstrip lines over the conductors of a circuit. The sliding is done in such way that the different available positions of the mobile structure control the phase shift along a certain transmission line of the circuit. The paper explains this mechanism and the implemented devices in depth; it describes its advantages and shows some examples of application.

CAD techniques for the electromagnetic design of monolithic millimetre-wave integrated circuits

It is well known that mm-waves have an important role to play in the rapid expansion of mobile and personal communications, mmic technology is an important factor since it can provide a means of mass producing the user terminal rf subsystems. Millimetre-wave integrated circuits do not yet however offer the high packing density and functionality which is now possible for lower frequency applications where lumped elements are used. This problem is influenced most of all by the extreme modelling difficulties encountered at frequencies above 30 GHz. This paper reviews the current state-of-the-art for cad techniques used in mmic design. It describes some limitations of the standard Smarttm library approach and looks at the application of commercial electromagnetic simulators in the design of both microstrip and cpw circuits.RésuméLes ondes millimétriques ont un rôle clef dans les communications mobiles. La technologie mmic fournit un moyen de fabriquer à grande échelle des composants pour les terminaux d’usager. Mais les circuits intégrés fonctionnant aux ondes millimétriques ne présentent pas encore la miniaturisation et les fonctions qui sont maintenant possibles à des fréquences inférieures en utilisant des éléments de circuits localisés. Ce probléme est en majeure partie dû aux difficultés de la modélisation aux fréquences supérieures à 30 GHz. L’article donne un aperçu de I’état de I’art des techniques cao utilisées pour la technologie mmic. // décrit ensuite quelques limitations de l’approche classique par bibliothèque Smarttm et étudie I’application de simulateurs électromagnétiques commerciaux à la conception de circuits en technologie microruban ou coplanaire (cpw).