Frequency response

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

Highly Stabilized Phase-Shifted Fiber Bragg Grating Sensing System for Ultrasonic Detection

Abstract: A phase-shifted fiber Bragg grating (PS-FBG) sensing system based on Pound–Drever–Hall (PDH) technique is proposed and experimentally demonstrated for ultrasonic detection. The sensing system is highly stabilized as the laser is frequency locked to the PS-FBG resonance using PDH technique. This scheme reduces the effect of laser intensity noise and enables high-sensitivity ultrasonic detection by monitoring the error signal of frequency detuning between the laser and the PS-FBG resonance. Response of the frequency-locked PS-FBG to ultrasound is done by testing the ultrasonic refection of a 0.4-mm plastic film, immersed in water. The sensor exhibits a high signal-to-noise ratio of 48 dB at 200 kHz and a noise-limited detectable strain of 8.7 $\text{p}\varepsilon $ above 10 kHz. Frequency response of PS-FBG from 100 kHz to 1 MHz was also characterized.

Autoregressive modeling of an indoor UWB channel

Abstract: Based on frequency domain measurements in the 4.375-5.625 GHz band a channel model for the frequency response of the indoor radio channel is introduced. In particular. a second-order Autoregressive (AR) model is proposed for frequency response generation of the ultra wide band indoor channel. A complete characterization of the model parameters is described along with probability distributions and dependencies between parameters.

Experimental Investigation and Design Optimization of Targeted Energy Transfer Under Periodic Forcing

Abstract: In this paper, the dynamic response of a harmonically forced Linear Oscillator (LO) strongly coupled to a Nonlinear Energy Sink (NES) is investigated both theoretically and experimentally. The system studied comprises a LO with an embedded, purely cubic NES. The behavior of the system is analyzed in the vicinity of 1 : 1 resonance. The complexification-averaging technique is used to obtain modulation equations and the associated fixed points. These modulation equations are analyzed using asymptotic expansion to study the regimes related to relaxation oscillation of the slow flow called Strongly Modulated Response (SMR). The zones where SMR occurs are computed using a mapping procedure. The Slow Invariant Manifolds (SIM) is used to derive a proper optimization procedure. It is shown that there is an optimal zone in the forcing amplitude-nonlinear stiffness parameter plane, where SMR occurs without having a high amplitude detached resonance tongue. Two experimental setups are presented. One is not optimized and has a relatively high mass ratio (≈ 13%) and the other one is optimized and exhibits strong mass asymmetry (mass ratio ≈ 1%). Different frequency response curves and associated zones of SMR are obtained for various forcing amplitudes. The reported experimental results confirm the design procedure, and the possible application of NES for vibration mitigation under periodic forcing.

Application of phasor measurement units to estimate power system inertial frequency response

Abstract: The inherent reduction in inertial frequency response resulting from a shift in generation mix towards renewables, is presenting a range of operational planning challenges for transmission system operators (TSOs) globally. Dictating the ability to maintain frequency following significant mismatches in supply and demand, it is of great consequence to the real-time operation of the power system. In this paper we discuss the estimation of system inertia constant using synchronised data, provided by installed phasor measurement units (PMUs). Results are presented from analysing the impact of over 50 transmission system events that were observed on the electricity transmission network of Great Britain.