BPSK to ASK signal conversion using injection-locked oscillators-part II: experiment

This paper demonstrates the feasibility of a new circuit for the conversion of binary phase-shift keying signals into amplitude-shift keying signals. In its simplest form, the converter circuit is composed by a power divider, a couple of second harmonic injection-locked oscillators, and a power combiner. The operation of the converter circuit relies on the frequency synchronization of both oscillators and the generation of an interference pattern by combining their outputs, which reproduces the original phase modulation. Two prototypes of the converter have been implemented. The first one is a hybrid version working in the 400-530-MHz frequency range. The second one has been implemented using multichip-module technology, and is intended to work in the 1.8-2.2-GHz frequency range.

A physical frequency-dependent compact model for RF integrated inductors

A frequency-dependent compact model for inductors in high ohmic substrates, which is based on an energy point-of-view, is developed. This approach enables the description of the most important coupling phenomena that take place inside the device. Magnetically induced losses are quite accurately calculated and coupling between electric and magnetic fields is given by means of a delay constant. The later coupling phenomenon provides a modified procedure for the computation of the fringing capacitance value, when the self-resonance frequency of the inductor is used as a fitting parameter. The model takes into account the width of every metal strip and the pitch between strips. This enables the description of optimized layout inductors. Data from experiments and electromagnetic simulators are presented to test the accuracy of the model.

Diseño e implementación de un filtro paso banda de banda estrecha con topología interdigital a frecuencias UHF y microondas

Desde el área de Ingeniería de RF del consorcio CELLS y en el marco de un convenio de colaboración firmado con el grupo de antenas y sistemas de microondas del Departamento de Telecomunicación e Ingeniería de sistemas de la ETSE (UAB), se ha planteado la evaluación y construcción de un filtro que formará parte del lazo de control en el módulo de RF. El objetivo es eliminar una señal espuria que se encuentra a la salida de un mezclador en banda lateral única, que por limitaciones en los inbalanceos de ganancia y fase, no termina de cancelar suficientemente la banda rechazada. Por lo tanto, el trabajo surge de la necesidad de diseñar un filtro capaz de obtener una respuesta paso banda centrada a 520 MHz, para atenuar un espurio existente a una frecuencia cercana (530 MHz). En consecuencia, estas especificaciones proporcionarán al filtro la característica de banda estrecha.

On the existence of hysteresis in the Kuramoto model with bimodal frequency distributions

We investigate the transition to synchronization in the Kuramoto model with bimodal distributions of the natural frequencies. Previous studies have concluded that the model exhibits a hysteretic phase transition if the bimodal distribution is close to a unimodal one, due to the shallowness the central dip. Here we show that proximity to the unimodal-bimodal border does not necessarily imply hysteresis when the width, but not the depth, of the central dip tends to zero. We draw this conclusion from a detailed study of the Kuramoto model with a suitable family of bimodal distributions.

Diseño de antenas UHF para aplicaciones RFID

Aquest projecte es basa en l'estudi, disseny i avaluació d'antenes per a aplicacions RFID a la banda UHF. Les etiquetes RFID estan compostes per un xip i una antena que han de presentar una bona adaptació per a aconseguir màxima transferència de potència. Els dos objectius principals en els diferents fases de disseny de cada antena han estat optimitzar les seves dimensions, i incrementar l'ample de banda.

Design of Novel Frequency Generation Circuit with Application to Ultra-Wideband Distributed Oscillators

Given the urgence of a new paradigm in wireless digital trasmission which should allow for higher bit rate, lower latency and tigher delay constaints, it has been proposed to investigate the fundamental building blocks that at the circuital/device level, will boost the change towards a more efficient network architecture, with high capacity, higher bandwidth and a more satisfactory end user experience. At the core of each transciever, there are inherently analog devices capable of providing the carrier signal, the oscillators. It is strongly believed that many limitations in today's communication protocols, could be relieved by permitting high carrier frequency radio transmission, and having some degree of reconfigurability. This led us to studying distributed oscillator architectures which work in the microwave range and possess wideband tuning capability. As microvave oscillators are essentially nonlinear devices, a full nonlinear analyis, synthesis, and optimization had to be considered for their implementation. Consequently, all the most used nonlinear numerical techniques in commercial EDA software had been reviewed. An application of all the aforementioned techniques has been shown, considering a systems of three coupled oscillator ("triple push" oscillator) in which the stability of the various oscillating modes has been studied. Provided that a certain phase distribution is maintained among the oscillating elements, this topology permits a rise in the output power of the third harmonic; nevertheless due to circuit simmetry, "unwanted" oscillating modes coexist with the intenteded one. Starting with the necessary background on distributed amplification and distributed oscillator theory, the design of a four stage reverse mode distributed voltage controlled oscillator (DVCO) using lumped elments has been presented. All the design steps have been reported and for the first time a method for an optimized design with reduced variations in the output power has been presented. Ongoing work is devoted to model a wideband DVCO and to implement a frequency divider.

Nuclear relaxation contribution to static and dynamic (infinite frequency approximation) nonlinear optical properties by means of electrical property expansions: Application to HF, CH4, CF4, and SF6

Electrical property derivative expressions are presented for the nuclear relaxation contribution to static and dynamic (infinite frequency approximation) nonlinear optical properties. For CF4 and SF6, as opposed to HF and CH4, a term that is quadratic in the vibrational anharmonicity (and not previously evaluated for any molecule) makes an important contribution to the static second vibrational hyperpolarizability of CF4 and SF6. A comparison between calculated and experimental values for the difference between the (anisotropic) Kerr effect and electric field induced second-harmonic generation shows that, at the Hartree-Fock level, the nuclear relaxation/infinite frequency approximation gives the correct trend (in the series CH4, CF4, SF6) but is of the order of 50% too small

Editorial: Language, frequency and bibliometric indexes

This editorial examines the actions undertaken in number 5 and announces two important changes for the numbers 6 and 7, namely frequency and languages. Furthermore, the use of some bibliometric indicators, such as impact factor and refusal rate, is critically analyzed.

Exploring the high frequency emission of radio loud X-ray binaries

We report millimetre-wave continuum observations of the X-ray binaries Cygnus X-3, SS 433, LSI+61 303, Cygnus X-1 and GRS 1915+105. The observations were carried out with the IRAM 30 m-antenna at 250 GHz (1.25 mm) from 1998 March 14 to March 20. These millimetre measurements are complemented with centimetre observations from the Ryle Telescope, at 15 GHz (2.0 cm) and from the Green Bank Interferometer at 2.25 and 8.3 GHz (13 and 3.6 cm). Both Cygnus X-3 and SS 433 underwent moderate flaring events during our observations, whose main spectral evolution properties are described and interpreted. A significant spectral steepening was observed in both sources during the flare decay, that is likely to be caused by adiabatic expansion, inverse Compton and synchrotron losses. Finally, we also report 250 GHz upper limits for three additional undetected X-ray binary stars: LSI+65 010, LSI+61 235 and X Per.

Frequency resolved admittance spectroscopy measurements on In0.52Al0.48As/InxGa1¿xAs/In0.52Al0.48As single quantum well structures

In this work a new admittance spectroscopy technique is proposed to determine the conduction band offset in single quantum well structures (SQW). The proposed technique is based on the study of the capacitance derivative versus the frequency logarithm. This method is found to be less sensitive to parasitic effects, such as leakage current and series resistance, than the classical conductance analysis. Using this technique, we have determined the conduction band offset in In0.52Al0.48As/InxGa1¿xAs/In0.52Al0.48As SQW structures. Two different well compositions, x=0.53, which corresponds to the lattice¿matched case and x=0.60, which corresponds to a strained case, and two well widths (5 and 25 nm) have been considered. The average results are ¿Ec=0.49±0.04 eV for x=0.53 and ¿Ec =0.51±0.04 eV for x=0.6, which are in good agreement with previous reported data.

Improvement of the quality factor of RF integrated inductors by layout optimization

A systematic method to improve the quality (Q) factor of RF integrated inductors is presented in this paper. The proposed method is based on the layout optimization to minimize the series resistance of the inductor coil, taking into account both ohmic losses, due to conduction currents, and magnetically induced losses, due to eddy currents. The technique is particularly useful when applied to inductors in which the fabrication process includes integration substrate removal. However, it is also applicable to inductors on low-loss substrates. The method optimizes the width of the metal strip for each turn of the inductor coil, leading to a variable strip-width layout. The optimization procedure has been successfully applied to the design of square spiral inductors in a silicon-based multichip-module technology, complemented with silicon micromachining postprocessing. The obtained experimental results corroborate the validity of the proposed method. A Q factor of about 17 have been obtained for a 35-nH inductor at 1.5 GHz, with Q values higher than 40 predicted for a 20-nH inductor working at 3.5 GHz. The latter is up to a 60% better than the best results for a single strip-width inductor working at the same frequency.

Firmground ichnofacies recording high-frequency marine flooding events (Langhian transgression, Vallè-Penedès Basin, Spain)

The decapod burrow Spongeliomorpha sudolica occurs associated with transgressive firmgrounds in the transition between Aragonian continental red beds and Langhian marine units in some of the inner sectors of the Vallès-Penedès Basin. This ichnospecies designates branching burrow systems with scratch marks in the walls produced by marine crustacean decapods. The occurrence of Spongeliomorpha represents an example of theGlossifungites ichnofacies. The several horizons where the traces are found are intercalated with continental red beds a few meters below the main transgressive surface, which is overlain by fossiliferous marine sandstones. The Spongeliomorpha-bioturbated layers record short, high frequency marine flooding surfaces that may be related either to actual sea-level changes or to variations in tectonic subsidence or sediment input. In any case, these flooding events punctuated the early phases of the Langhian transgression in the basin.

Frequency dynamics of gain-switched injection-locked semiconductor lasers

The frequency dynamics of gain-switched singlemode semiconductor lasers subject to optical injection is investigated. The requirements for low time jitter and reduced frequency chirp operation are studied as a function of the frequency mismatch between the master and slave lasers. Suppression of the power overshoot, typical during gain-switched operation, can be achieved for selected frequency detunings.