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A new design methodology for radiofrequency circuits is presented that includes electromagnetic (EM) simulation of the inductors into the optimization flow. This is achieved by previously generating the Pareto-optimal front (POF) of the inductors using EM simulation. Inductors are selected from the Pareto front and their S-parameter matrix is included in the circuit netlist that is simulated using an RF simulator. Generating the EM-simulated POF of inductors is computationally expensive, but once generated, it can be used for any circuit design. The methodology is illustrated both for a singleobjective and a multiobjective optimization of a low noise amplifier

Changes in electromagnetic energy absorption were studied in the presence of subcutaneous antenna devices implanted for biotelemetry applications. We examined the influence on energy absorption of these devices as passive metallic implants when incoming RF energy is present. We aim to contribute to the optimization of the implant location in order to reduce a possible energy increase on tissues. The research was carried out using electromagnetic modeling based on the finite-difference time-domain method. The calculations were performed in terms of electric field and SAR distributions calculated for five different frequency bands (from 0.9 to 17 GHz) covering most current telecommunications standards. The focus was on both far-field and near-field exposure. The results lead us to propose the subcutaneous zone nearest to the surface of the skin as the most appropriate place to locate these devices.

This paper presents a new method and circuit for the conversion of binary phase-shift keying (BPSK) signals into amplitude shift keying signals. The basic principles of the conversion method are the superharmonic injection and locking of oscillator circuits, and interference phenomena. The first one is used to synchronize the oscillators, while the second is used to generate an amplitude interference pattern that reproduces the original phase modulation. When combined with an envelope detector, the proposed converter circuit allows the coherent demodulation of BPSK signals without need of any explicit carrier recovery system. The time response of the converter circuit to phase changes of the input signal, as well as the conversion limits, are discussed in detail.

By using a Monte Carlo simulator, the static and dynamic characteristics of 50-nm-gate AlInAs-GaInAs /spl delta/-doped high-electron mobility transistors (HEMTs) are investigated. The Monte Carlo model includes some important effects that are indispensable when trying to reproduce the real behavior of the devices, such as degeneracy, presence of surface charges, T-shape of the gate, presence of dielectrics, and contact resistances. Among the large quantity of design parameters that enter the fabrication of the devices, we have studied the influence on their performance of two important factors: the doping level of the /spl delta/-doped layer, and the width of the devices. We have confirmed that the value of the /spl delta/-doping must be increased to avoid the reduction of the drain current due to the depletion of the channel by the surface potential. However, a higher /spl delta/-doping has the drawback that the frequency performance of the HEMTs is deteriorated, and its value must be carefully chosen depending on the system requirements in terms of delivered power and frequency of operation. The reduction of the device width has been also checked to improve the cutoff frequencies of the HEMTs, with a lower limit imposed by the degradation provoked by the offset extrinsic capacitances.

In order to improve the quality of its time and frequency services, the Mexican Power Electric Company (via its Test on Equipment and Materials Laboratory), requires traceability to Time and Frequency Mexican Primary Standards, with this purpose, the common-view (CV) technique, using a TTR-6A GPS receiver, has been implemented between LAPEM and the Time and Frequency Division of CENAM. In this paper we present the results of this Mexican comparison of time standards between these two national laboratories.

This paper proposes a method for the diagnosis of roll eccentricity influence on the strip thickness at the exit of a finishing hot strip mill (FHSM). Each exit strip thickness defect is related to one roll of the FHSM, allowing the implementation of an optimal policy for the substitution and maintenance of the rolls, while maintaining the required quality level of the strip. This policy allows the minimization of roll changes and the concentration of several changes at the same time, reducing production costs. Fuzzy logic is used to compare spectra, looking for common patterns, which enables a totally-automated diagnostic system. Likewise, as part of the solution, a novel estimate of roll eccentricity, based on a least-squares algorithm has been developed, which provides higher accuracy than classical algorithms as well as a drastic reduction in the time required to perform eccentricity tests.

An accurate and highly efficient fast-Fourier-based full-vectorial beam propagation method (BPM) with perfectly matched layer absorbing boundary conditions is presented. Full vectorial results obtained for highly guiding z-variant structures, such as a spot size converter and a Y-branch in rib technology, show that accurate results can be obtained with reduced computational effort, thus making this technique an interesting alternative to other existing BPM strategies.

Molecular sieves of the type CoAPO-5 have been studied by TEM and ac susceptibility measurements. In the as-synthesised state the material is paramagnetic due to the isolated cobalt ions and microstructurally it looks very homogeneous. After calcination the system develops very small cobalt-containing particles of A size between 1 and 3 nm, is paramagnetic at high temperature, superparamagnetic below about 20 K and starts to experience particle blocking below about 5 K. The tendency of cobalt to produce oxides and hydroxides of antiferromagnetic nature, together with the observed reduction of the effective moment below 20 K suggests that this is indeed a paramagnetic-superparamagnetic transition of antiferromagnetic particles. The susceptibility data have been used to estimate the degree of intraparticle spin uncompensation.