Transfer function

About: Transfer function is a research topic. Over the lifetime, 14362 publications have been published within this topic receiving 214983 citations. The topic is also known as: system function & network function.

Image enhancement in optical coherence tomography using deconvolution

Abstract: The present invention provides an improved optical coherence tomography system and involves estimating the impulse response (which is indicative of the actual reflecting and scattering sites within a tissue sample) from the output interferometric signal of an interferometer according to the following steps: (a) acquiring auto-correlation data from the interferometer system; (b) acquiring cross-correlation data from the interferometer system having the biological tissue sample in the sample arm; and (c) processing the auto-correlation data and the cross correlation data to produce an optical impulse response of the tissue The impulse response may be obtained from the cross-correlation and auto-correlation data by: (d) obtaining an auto-power spectrum from the auto-correlation data by performing a Fourier transform on the auto-correlation data; (e) obtaining a cross-power spectrum from the cross-correlation data by performing a Fourier transform on the cross-correlation data; (f) obtaining a transfer function of the LSI system by taking a ratio of the cross-power spectrum to the auto-power spectrum; and (g) obtaining the optical impulse response of the LSI system by performing an inverse-Fourier transform on the transfer function Preferably, coherent demodulation is used in combination with the above deconvolution technique to resolve closely-spaced reflecting sites in the sample By utilizing both the magnitude and phase data of the demodulated interferometric signals, the OCT system of the present invention is able to distinguish between closely spaced reflecting sites within the sample

String Instability in Classes of Linear Time Invariant Formation Control With Limited Communication Range

Abstract: This paper gives sufficient conditions for string instability in an array of linear time-invariant autonomous vehicles with communication constraints. The vehicles are controlled autonomously and are subject to a rigid or semi-rigid formation policy. The individual controllers are assumed to have a limited range of forward and backward communication with other vehicles. Sufficient conditions are given that imply a lower bound on the peak of the frequency response magnitude of the transfer function mapping a disturbance to the leading vehicle to a vehicle in the chain. This lower bound quantifies the effect of spacing separation policy, intervehicle communication policy, and vehicle settling response performance. These results extend earlier works to give a unified treatment of heterogeneous, non-nearest neighbor communication and semi-rigid one-dimensional formation control.

An alternative approach to the realization of network transfer functions: The N-path filter

Abstract: A particular time-varying network consisting of several parallel transmission paths, each containing input and output modulators, is described and analyzed. It is shown that, under certain conditions, the network may be characterized by a transfer function. A particular form of this transfer function yields periodic filtering characteristics over a limited frequency band without employing distributed elements. Techniques are also presented for realizing highly selective band-pass filters without the use of magnetic elements. Some practical applications are discussed in detail and experimental verification is presented.

Analysis of an AC-to-DC voltage source converter using PWM with phase and amplitude control

Abstract: A comprehensive analysis is presented of a pulse-width modulated AC-to-DC voltage source converter under phase and amplitude control. A general mathematical model of the converter, which is discontinuous, time-variant, and nonlinear, is first established. To obtain closed-form solutions, the following three techniques are used: Fourier analysis; transformation of reference frame; and small-signal linearization. Three models, namely, a steady-state DC model, a low-frequency small-signal AC model, and a high-frequency model, are consequently developed. Finally, three solution sets, namely, the steady-state solution, various dynamic transfer functions, and the high-frequency harmonic components, are obtained from the three models. The theoretical results were verified experimentally. >

A noniterative method for identification using Hammerstein model

Abstract: A noniterative method developed by Hsia for the particular case where the transfer function in the Hammerstein model has no zeros is extended to the general case where the transfer function may have zeros. Numerical examples show that the computation time by this method is considerably less than by the iteratire procedure proposed by Narendra and Gallman while the accuracy of the estimates is comparable.