Butterworth filter

About: Butterworth filter is a research topic. Over the lifetime, 6187 publications have been published within this topic receiving 69070 citations.

Error-rate performance of optical amplifiers with Fabry-Perot filters

Abstract: The error-rate performance of an ON-OFF keyed lightwave receiver having an optical amplifier followed by a Fabry-Perot filter is analysed. Receivers with sampling and with integrate-and-dump threshold comparison are compared with the well known result for a matched optical filter. The Fabry-Perot filter decreases the sensitivity at 10/sup -9/error rate from 76 to 89 photon/bit (peak) with optimum optical filter bandwidth and postdetection integration time. >

Analysis and Design of Two Layered Ultra Wide Band Filter

Abstract: Design of an Ultra Wide Band (UWB) filter over 3.1 GHz to 10.6 GHz using broad side coupled and spur lines in microstrip medium suitable for UWB communications has been presented in this paper. Parameters of broad side coupled lines have been appropriately chosen to achieve ultra wide band response. Spur lines have been incorporated at the input and output feed lines of the filter to improve the stop band rejection characteristics of the filter. Filter has been analyzed based on circuit models and full wave simulations. Experimental results of the filter designed using the proposed structure has been verified against the results obtained from circuit models and full wave simulations. The results match satisfactorily. Stop band rejection of better than 20 dB was obtained over the frequencies of 13 GHz to 18.2 GHz. Overall size of the filter is 40 x 18 x 0.787 mm(3).

Investigation on the Behavior of Noise in Asynchronous Spectra in Generalized Two-Dimensional (2D) Correlation Spectroscopy and Application of Butterworth Filter in the Improvement of Signal-to-Noise Ratio of 2D Asynchronous Spectra

Abstract: The behavior of noise in asynchronous spectrum in generalized two-dimensional (2D) correlation spectroscopy is investigated. Mathematical analysis on the noise of 2D spectra and computer simulation on a model system show that the fluctuation of noise in a 2D asynchronous spectrum can be characterized by the standard deviation of noise in 1D spectra. Furthermore, a new approach to improve a signal-to-noise ratio of 2D asynchronous spectrum by a Butterworth filter is developed. A strategy to determine the optimal conditions is proposed. Computer simulation on a model system indicates that the noise of 2D asynchronous spectrum can be significantly suppressed using the Butterworth filtering. In addition, we have tested the approach to a real chemical system where interaction between berberine and β-cyclodextrin is investigated using 2D UV–vis asynchronous spectra. When artificial noise is added, cross peaks that reflect intermolecular interaction between berberine and β-cyclodextrin are completely masked by n...

Phase-locked loop having separate smoothing and loop filters

Abstract: A PLL comprising a phase comparator circuit for detecting the phase of a pulse signal based upon the input signal and the phase of a pulse signal based upon the output signal, a smoothing filter for smoothing the output of the phase comparator circuit, a loop filter for controlling the oscillation frequency on the basis of the smoothing filter, and a voltage controlled oscillator circuit for sending out the output signal having a frequency corresponding to the voltage based upon the output of the loop filter. Since the smoothing filter is separated from the loop filter, time constants of the smoothing filter and the loop filter can be set independently and with precision. If the time constant of the smoothing filter is chosen to be extremely small, for example, the time constant of the phase-locked loop is defined by the time constant of the loop filter. It is thus possible to define the time constant of the phase-locked loop by only selecting the time constant of the loop filter. Further it is possible to both suppress the jitter of the phase-locked loop and reduce the frequency ripple, for example.

Interpolator/decimator filter structure and a notch filter therefor

Abstract: A filter structure (Figure 4) including a notch filter (C) des­ igned to have a transmission zero at a frequency slightly dis­ placed from one half of the lower sampling rate of the inter­ polator/decimator, and thus providing increase in attenuation at the half-rate frequency. The notch filter (C) is comprised of two like all-pass-­ network filters (31 and 33) and has feed forward and feedback connections (39 and 41), the latter connection (41) including a coefficient multiplier (43). The feedback connection (41) is made between a tapped output (T) of the second of the network filters, filter (41) and an input node (35). The tapped filter (33) is characterised by throughput and a tapped output transform functions X(Z) and Y(Z) given by the following expressions:- X(Z) = [Z⁻¹ - K] / [1 - KZ⁻¹]; and, Y(Z) = α Z⁻¹ / [1 - KZ⁻¹]; where Z⁻¹ is the unit delay operator, K the multiplier coeffic­ ient and, α, a structure dependant constant.