2,725 research outputs found
Multiple Order Dual-Band Active Ring Filters with Composite Right/Left Handed Cells
In this paper, a novel dual-band active filter topology is presented. The non-linear phase response of a composite right/left-handed cell is used to achieve the desired dual-band performance. Additionally, the proposed structure based on coupled ring resonators yields a very compact solution in which high-order implementations can be easily obtained by cascading multiple rings. The theoretical principles of this type of filters are analyzed in detail. Finally, three prototypes based on first-, second- and third-order structures validate the feasibility of this type of filters. Good agreement between simulations and measurements has been achieved
Noise Figure Measurement of Differential Amplifiers Using non-Ideal Baluns
This paper analyzes the noise and gain measurement of microwave differential amplifiers using two passive baluns. A general model of the baluns is considered, including potential losses and phase/amplitude unbalances. This analysis allows de-embedding the actual gain and noise performance of the isolated amplifier by using single-ended measurements of the cascaded system and baluns. Finally, measured results from two amplifier prototypes are used to validate the theoretical principles
Evanescent waves and deaf bands in sonic crystals
The properties of sonic crystals (SC) are theoretically investigated in this work by solving the inverse problem k(Âż) using the extended plane wave expansion (EPWE). The solution of the resulting eigenvalue problem gives the complex band structure which takes into account both the propagating and the evanescent modes. In this work we show the complete mathematical formulation of the EPWE for SC and the supercell approximation for its use in both a complete SC and a SC with defects. As an example we show a novel interpretation of the deaf bands in a complete SC in good agreement with multiple scattering simulations. © 2011 Copyright 2011 Author(s).This work was supported by MCI-Secretaria de Estado de Investigacion (Spanish government) and the FEDER funds, under grant MAT2009-09438. LMGR would like to thank the UPV for the grant PAID-00-11. VRG is grateful for the support of "Programa de Contratos Post-Doctorales con Movilidad UPV (CEI-01-11)."Romero GarcĂa, V.; GarcĂa Raffi, LM.; SĂĄnchez PĂ©rez, JV. (2011). Evanescent waves and deaf bands in sonic crystals. AIP Advances. 1(4):416011-416019. doi:10.1063/1.3675801S4160114160191
Modelos predictivos de la deformaciĂłn permanente de las capas de base de materiales granulares sueltos empleados en los firmes flexibles
Este V Congreso tivo lugar en León, entre o 30 de maio e o 1 de xuño de 2000.[Resumen:] Uno de los principales objetivos de la investigación del comportamiento de los
firmes flexibles de carreteras consiste en establecer relaciones constitutivas que permitan
dar predicciones exactas de la deformaciĂłn permanente de los materiales granulares sueltos
que conforman las capas de base. Durante años, diversos investigadores han intentado
perfilar procedimientos que predigan la deformaciĂłn permanente en estos materiales. En
esta comunicaciĂłn se va a realizar una breve descripciĂłn de los diferentes modelos
constitutivos
Comportamiento resiliente en las capas de base de materiales granulares
Este V Congreso tivo lugar en León, entre o 30 de maio e o 1 de xuño de 2000.[Resumen:] La realizacion de modelos es un requerimiento importante para estudiar el comportamiento resiliente de los materiales granulares. Muchos investigadores han perfilado diferentes procedimientos para predecir la respuesta resiliente de dichos materiales. En la presente comunicacion se realiza una breve descripcion de los modelos de prediccion del comportamiento resiliente de este tipo de materiales bajo las cargas del trafico. Se concluye afirmando que se necesita un mayor esfuerzo en el desarrollo de modelos y procedimientos que tengan una base teorica solida y una aplicacion util y general
Algunas notas sobre el comportamiento de las zahorras en los firmes
[Resumen:] Al hilo de lo discutido en el reciente V Congreso Nacional de Firmes, sobre las capas de base de los firmes, en este artĂculo se exponen las misiones de las bases granulares en cada tipo de firme, con algunas notas de la importancia de los riegos de imprimaciĂłn y de evitar la segregaciĂłn, como principal enemigo de la respuesta de estos materiales a lo largo de su vida. Finalmente, se exponen algunas conclusiones que resumen estas misiones, y combaten algunas concepciones falsas que pueden escucharse en algunas ocasiones
Dual-Band Tunable Recursive Active Filter
This letter presents a novel recursive active filter topology that provides dual-band performance, with independent tuning capability in both bands. The dual-band operation is achieved by using two independent feedback lines. Additionally, linear phase shifters based on left-handed cells are included in these two branches in order to tune the center frequency of both pass bands
Ausencia de evidencia de simetrĂa en palomas tras entrenamiento en mĂșltiples ejemplares
Antecedentes: se realizĂł un experimento con palomas durante 46 meses para contrastar la hipĂłtesis del entrenamiento en mĂșltiples ejemplares (MET) en la derivaciĂłn de simetrĂa. SegĂșn esta hipĂłtesis, la simetrĂa se deriva progresivamente despuĂ©s de entrenar mĂșltiples ejemplos de relaciones directas e inversas entre estĂmulos arbitrarios. MĂ©todo: cuatro palomas fueron entrenadas en discriminaciones condicionales arbitrarias directas (ej., A1-B1, A2-B2) e inversas (ej., B1-A1; B2-A2). Una vez que aprendieron una reversiĂłn completa (ej., AB y BA), se entrenĂł otra reversiĂłn con estĂmulos diferentes (ej., CD y DC, etc.). Los sujetos fueron asignados a dos conjuntos de estĂmulos; el orden de aprendizaje de muestras y comparaciones fue contrabalanceado. Resultados: las palomas aprendieron entre 4 y 24 discriminaciones, pero ninguna mostrĂł simetrĂa. La discriminabilidad de las muestras y las comparaciones fue determinante porque afectĂł a las discriminaciones directas de manera diferente a las discriminaciones inversas. Conclusiones: a pesar de los resultados negativos, este estudio puede contribuir al desarrollo de la investigaciĂłn en MET y simetrĂa: se describen algunas lecciones aprendidas acerca del diseño de experimentos de larga duraciĂłn con numerosos estĂmulos y se discuten algunas estrategias para controlar la discriminabilidad de los estĂmulos que pueden contribuir a facilitar la derivaciĂłn de simetrĂa.Background: An experiment with pigeons was conducted for 46 months in order to test the multiple-exemplar training (MET) hypothesis of symmetry derivation. According to this hypothesis, symmetry is progressively derived after an extensive training of multiple examples of direct and inverse relations among arbitrary stimuli. Method: Four pigeons were given extensive training in direct (e.g., A1-B1; A2-B2) and inverse (e.g., B1-A1; B2-A2) arbitrary conditional discriminations. Once pigeons learned a complete reversal (e.g., AB and BA), a new reversal with different stimuli was trained (e.g., CD and DC, etc.). Subjects were assigned to two different stimulus sets, and sample-comparison order was counterbalanced. Results: Pigeons learned between 4 and 24 conditional discriminations, but none showed evidence of symmetry. Discriminability of samples and comparisons was identified as an important factor because it affected direct and inverse discriminations differently. Conclusions: Despite the negative results reported, this study provides some insights that might help to improve current research on MET and symmetry: We describe some lessons learned about the design of long-term experiments involving a high number of stimuli and finally, we discuss some control strategies for stimulus discriminability that might also contribute to facilitate symmetry derivation in pigeons
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