We present results for the coupling efficiencies of the HE11 mode of monomode optical fiber joints with misalignements in the axis or different radius of the core, obtained by a modal analysis of the discontinuity.
Armesto, A. Conferència: Elementos para la comprensión de la forma del Plano Cerdà de 1859. Dins del III Seminario Internacional de Arquitectura Fecha de presentación: 1980-10-01 Presentación de trabajo en congreso
The Importance Sampling Technique is a method for reducing the computational effort in Montecarlo simulations for obtaining the relative frequency of an event having a very low probability. While this method is well known in general Operations Research /1//2//3/ and Radar /4//5//6//7//8//9//10/, it has not been considered in digital communication problems. This paper aims to introduce the Importance Sampling concept in this communication context.
The analysis of transmission line tapers is approached through an integral equation formulation (equivalent to a series solution for propagation through an inhomogeneous medium given by Bremmer) which can be used to iteratively obtain approximations, the first of which is the formula ordinarily used in the analysis and synthesis problems. From the second, an estimation of the error involved in the computation of the reflection is obtained and studied in detail for the exponential and the Chebychev tapers. This latter is found to be very sensitive to the approximations involved far large mismatches and/or low residual reflections. Formulas and graphs are given that allow one to assess the accuracy and to improve the design.
Dans ce papier, on a obtenu des bornes inférieure et supérieure de la probabilité d 'erreur par symbole dans un systemè de transmission numérique par Fibre Optique. Pour celà, nous avons employé une simplification de la méthode exhaustive qui permet de connaitre, pour chaque message transmis, la valeur de l'interférence intersymboles et du bruit de grenaille. L'approsimation gaussienne sur le bruit de grenaille permet une réduction considérable du temps de calcul. La précision sur la probabilité d'erreur, mesurée par l'écart entre les bornes supérieure et inférieure, augmente avec le nombre de symboles du message numérique pris en compte.
Enfin, les résultats obtenus permettent de déterminer l'espacement des répéteurs.
A new approach in the problem of phase detectors is presented. The procedure is started from the optimum design of digital phase locked loop (DPLL) and some fundamental aspects as the state equations for the communication model are preserved. The purpose of this paper is to point out the relationships between MAP and optimum estimators. We also show how previous adaptative linear filter of the signal error can be introduced to achieve high levels of quality on the estimate without great computational load. This preprocessing can be interpreted in terms of dissimilarity between input signal and noise spectrum. Finally, we give a heuristic exposition which sacrifices some amount of rigor in order to gain insight into the basic ideas involved.
Computing the exact carrier phase-jitter delivered from the recovery circuit in a QPSK-TDMA satellite system is cumbersome and has not been sufficiently investigated due to the analytical difficulties with the non linearities. In this paper, we analyse a QPSK system model that includes transmitter and receiver filters with optimal Nyquist pulse shaping, and a 4th power law nonlinearity. The carrier filtering is accomplished by a single tuned filter. The analytical method is carried out by using a Volterra series approache and satisfactory results are obtained.
A theoretical analysis of slot antennas excited by stripline is presented, with calculation of impedance and resonance frequency for different positions of the slot. Mutual effects are taken into account and results for different configurations are obtained.
The moments method is applied to a Green's function formulation of the static solution of a microstrip line with pulses as basis functions and Dirac deltas or pulses as testing functions. The system capacitance per unit length is computed both directly from the charge distribution and from a variational expression and the results compared.
The pulses are defined on subintervals of length in geometric progression, and the effect of the ratio on the results analysed. Conclusions about its optimum value are also given.
The condition of the system, using the 1 norm, is studied as a test of the quality of the results. The strong connection between its behaviour and both the convergence of the capacitance and the charge distribution is shown.
Los procedimientos de detección no paramétrica se presentan como una sencilla y eficaz alternativa del empleo de métodos óptimos en casos de modelado incompleto o entorno variante. En el presente artículo, se justifica tal posibilidad, dedicando especial atención a dos esquemas particulares que han mostrado su utilidad en sistemas Radar y que pueden ser extendidos a otros ámbitos de aplicación.
Conditions for existence of higher-order modes of the reduced wave equation V2 u + Au = 0 on semi - infinite domains subjected to different boundary conditions are presented and applied to the slot line. Bounds for the lowest eigenvalues are obtained using the Method of Moments.
A theoretical analysis of the double-slug transmission line tuner and the microstrip discs is developed based on two separate models: a distribuited impedance transforming model and a lumped shunt susceptance model. No loss conditions are assumed for both cases. These model permit an insight into the workings of the tuners and allow questions on the impedance matching and bandwidth performance of the tuners to be answered.
We present the principles of operation of near field antenna ranges and general expressions for the calculation of the far field, from measurements on plane surfaces, focusing on the limitations of the different aproaches. We introduce algorithmes with different possibilities of utilization which were applied to an X-Band slotted antenna array and the results are compared with direct measurements in the far field.
A method for de characterization of solid state amplifying devices has been developed thats allows one the determination of the input and o output amplifier, matching networks for low noise, maximum power transfer and maximum output power compatible with system linearity. The method as the same for the three purposes permithings the small signal as well the large signal device characterization. The work assumes that the device polarization is fixed by the particular application.
Whittaker's (or Shannon 's) Sampling Theorem is a well-known interpolation formula that has been extended in many directions. In this paper, we introduce two new formulations:
-The first follows Papoulis' Generalized Sampling Expansion for reconstructing a signal from regular samples of N(linear, time-invariant) functionals of it, taking the samples at 1/N the Nyquist rate; but generalizing it for including linear T- periodically time-varying systems. This way is in close relation with works that extend sampling in other directions.
-The second generalizes Linden's proof of Kohlenberg's sampling for a bandpass signal, in order to maintain the minimum sampling rate (in the average) and to obtain a separate interpolation of the in-phase and quadrature components of the signal. This follows Grace- Pitt-Brown's theory of bandpass sampling.
A new method for designing digital equalizers with simultaneous specification of magnitude and phase is introduced. The approximation is carried out using minimax error criteria. The method is eficient in iterations number and guarantees stability for the designed equalizer.