Frequency response

About: Frequency response is a research topic. Over the lifetime, 25705 publications have been published within this topic receiving 332249 citations.

Monolithic optical waveguide filters based on Fourier expansion

Abstract: In accordance with the invention, a new type of monolithic optical waveguide filter comprises a chain of optical couplers of different effective lengths linked by differential delays of different lengths. The transfer of the chain of couplers and delays is the sum of contributions from all possible optical paths, each contribution forming a term in a Fourier series whose sum forms the optical output. A desired frequency response is obtained by optimizing the lengths of the couplers and the delay paths so that the Fourier series best approximates the desired response. The filter is advantageously optimized so that it is insensitive to uncontrolled fabrication errors and is short in length. The wavelength dependence of practical waveguide properties is advantageously incorporated in the optimization. Consequently, the filter is highly manufacturable by mass production. Such filters have been shown to meet the requirements for separating the 1.3 and 1.551 μm telecommunications channels and for flattening the gain of Er amplifiers.

Design Considerations for Frequency Responsive Grid Friendly TM Appliances

Abstract: This paper addresses design considerations for frequency responsive grid friendlytrade appliances (FR-GFAs), which can turn on/off based on frequency signals and make selective low-frequency load shedding possible at appliance level. FR-GFAs can also be treated as spinning reserve to maintain a load-to-generation balance under power system normal operation states. The paper first presents a statistical analysis on the frequency data collected in 2003 in Western Electricity Coordinating Council (WECC) systems. Using these frequency data as an input, the triggering frequency and duration of an FR-GFA device with different frequency setting schemes are simulated. Design considerations of the FR-GFA are then discussed based on simulation results

A Miniaturized Flexible Frequency Selective Surface for X-Band Applications

Abstract: In this paper, a novel and miniaturized band-stop frequency selective surface (FSS) is presented. This FSS provides effective shielding in X-band, with attenuation of at least 56 dB. The proposed FSS provides 3-dB fractional bandwidth of 48% which is necessary to cover X-band. Moreover, the proposed design is polarization independent as it provides a stable frequency response at normal and oblique angles of incidences for both perpendicular TE and parallel TM wave modes. The copolarized and cross-polarized scattering parameter $S_{21}$ is analyzed at the selected band-stop/notch frequencies. More importantly, the proposed FSS is suitable for conformal applications and hence finds wider employability. A prototype of the proposed FSS is fabricated and tested. The measured results are in good agreement with the simulated results.

Analysis of switched capacitive networks

Abstract: An efficient method is presented for the exact analysis of networks containing capacitors, independent and dependent voltage sources, and switches. Both continuous and piecewise-constant arbitrary inputs are handled, and solutions are presented for both transient response and frequency response. The switching pattern can be periodic (with any number of subintervals per period) or nonperiodic. The formulation proposed can be efficiently implemented on the computer and provides for user convenience; only one network topology and the switching schedule must be specified (as opposed to specifying as many topologies as there are switch position combinations). The method is especially well suited for the analysis of the recently introduced switched capacitor filters and charge redistribution circuits.

Nonlocal strain gradient nonlinear resonance of bi-directional functionally graded composite micro/nano-beams under periodic soft excitation

Abstract: With the aid of advanced design techniques, functionally graded materials as promising new materials can be fabricated into various micro/nano-structures to acquire stronger mechanical performance. In this work, the size-dependent nonlinear primary resonance of periodic soft excited micro/nano-beams made of bi-directional functionally graded materials (2D-FGMs) is studied. To accomplish this end, the nonlocal strain gradient theory of elasticity is utilized within the framework of the refined hyperbolic shear deformation beam theory to construct a size-dependent beam model. On the basis of the variational approach using the principle of Hamilton, the non-classical differential equations of motion are achieved. Thereafter, a discretization scheme based numerical solving process via generalized differential quadrature method (GDQM) together with the pseudo-arclength continuation technique, the nonlocal strain gradient frequency response and amplitude response associated with the nonlinear primary resonance of 2D-FGM micro/nano-beams with different boundary conditions are obtained. It is displayed that the nonlocal size dependency makes a reduction in the oscillation amplitudes associated with both of the bifurcation points, but the strain gradient size effect causes to increase them. These patterns are more significant for the second bifurcation point and for the simply supported-simply supported boundary conditions in comparison with the clamped-clamped ones. Also, it is observed that by increasing the value of both of the axial and lateral material property gradient indexes, the peak of the oscillation amplitude and its associated excitation frequency increase.