Topic
Frequency response
About: Frequency response is a research topic. Over the lifetime, 25705 publications have been published within this topic receiving 332249 citations.
Papers published on a yearly basis
Papers
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01 Apr 1957
TL;DR: In this paper, a photocell is described that uses the lateral effect and can detect the position of a light spot to less than 100 A. The sensitivity of the cell is approximately 200 microamperes per lumen and its frequency response is about the same as that of junction transistors.
Abstract: The effect of illumination of a semiconductor junction is, as is well-known, a photovoltage between the two sides of the junction. In this article it will be shown that a nonuniform illuimination gives a lateral photovoltage parallel to the junction in addition to the (transverse) photovoltage mentioned above. A photocell will be described that uses the lateral effect and can detect the position of a light spot to less than 100 A. By utilizing an associated lens or aperture, one can measure an angular motion smaller than 0.1 second of arc. The output voltage of the cell is a linear function of the position of the light spot, with zero output for the light spot in the center, reversing in sign when the light spot changes from one side to the other of the center position. The linearity is better than 1.5 per cent over a distance of 0.030 inch. The equivalent noise resistance of the cell is equal to its output resistance, approximately 100 ohms. The sensitivity of the cell is approximately 200 microamperes per lumen and its frequency response is about the same as that of junction transistors. The response curve can be shifted by the application of a voltage between the base contacts. This is an electronic equivalent of a mechanical translation of the cell. It is also possible to do the equivalent of "chopping" the light by applying a modulating voltage to the alloyed dot.
345 citations
TL;DR: A systematic method is proposed to obtain the highest stability and avoidance of closed-loop anomalous peaks: it is achieved by the minimization of the inverse of the Nyquist trajectory distance to the critical point, i.e., the sensitivity function.
Abstract: The following two types of resonant controllers are mainly employed to obtain high performance in voltage-source converters: 1) proportional + resonant (PR) and 2) vector proportional + integral (VPI). The analysis and design of PR controllers is usually performed by Bode diagrams and phase-margin criterion. However, this approach presents some limitations when resonant frequencies are higher than the crossover frequency defined by the proportional gain. This condition occurs in selective harmonic control and applications with high reference frequency with respect to the switching frequency, e.g., high-power converters with a low switching frequency. In such cases, additional 0-dB crossings (phase margins) appear; therefore, the usual methods for simple systems are no longer valid. In addition, VPI controllers always present multiple 0-dB crossings in their frequency response. In this paper, the proximity to the instability of PR and VPI controllers is evaluated and optimized through Nyquist diagrams. A systematic method is proposed to obtain the highest stability and avoidance of closed-loop anomalous peaks: it is achieved by the minimization of the inverse of the Nyquist trajectory distance to the critical point, i.e., the sensitivity function. Finally, several experimental tests, including an active power filter that operates at a low switching frequency and compensates harmonics up to the Nyquist frequency, validate the theoretical approach.
343 citations
TL;DR: In this paper, the frequency, damping, strength, and relative phase of the modal components present in a recorded signal are estimated using Prony analysis and a model construction based on response data obtained through large-scale tests of the western US power system.
Abstract: It has been shown by J.F. Hauer et al. (ibid., vol.5, p.80-90, Feb. 1990) that Prony analysis can be very effective in response-based modal analysis of noise-free linear time-invariant (LTI) systems. This methodology extends Fourier analysis by directly estimating the frequency, damping, strength, and relative phase of the modal components present in a recorded signal. This earlier work is extended, concentrating upon power system planning applications, for stability program outputs. Results are presented for modal analysis and detailed model construction based on response data obtained through large-scale tests of the western US power system. An optimal modeling program, SYSFIT, is used to supplement the measurements. >
342 citations
01 Mar 1971
TL;DR: In this article, the authors developed models to describe delay lines and compared the predictions of these theories with several experimental filters, including band-pass filters and dispersive delay lines, in the UHF range, and the frequency response is determined by the finger spacing and overlap of the interdigital comb structures used as input and output transducers.
Abstract: Acoustic surface waves offer several advantages in the construction of delay lines and filters in the UHF range. In these devices the frequency response is determined by the finger spacing and overlap of the interdigital comb structures used as input and output transducers. Models are developed to describe these devices, and the predictions of these theories are compared with several experimental filters, including band-pass filters and dispersive delay lines.
338 citations
TL;DR: A path loss model as well as a second-order autoregressive model is proposed for frequency response generation of the UWB indoor channel and results of frequency-domain channel sounding in residential environments are described.
Abstract: This paper describes the results of frequency-domain channel sounding in residential environments. It consists of detailed characterization of complex frequency responses of ultra-wideband (UWB) signals having a nominal center frequency of 5 GHz. A path loss model as well as a second-order autoregressive model is proposed for frequency response generation of the UWB indoor channel. Probability distributions of the model parameters for different locations are presented. Also, time-domain results such as root mean square delay spread and percent of captured power are presented.
336 citations