Concept Of Digital Filters Research Articles

A General Characterizing Method for Ring Resonators Based on Low Coherence Measurement

Optical filters are crucial devices for wavelength channel selecting in wavelength-division-multiplexed fiber-optic communication networks. Measuring the inner physical parameters of optical filters is significant for analyzing emerging new and more complex structures. This paper proposed a general and easy-to-operate method to extract physical parameters for complex filter structures with optical low-coherence measurement. By treating optical filters with digital filter concepts and z-transform analysis, we can build the relation between interferogram peak values and transfer function coefficients with brief linear equations. These equations can be used to derive the exact expression of transfer functions, which can manipulate the physical parameters. For a given filter structure, according to relations between transfer functions and physical parameters, the physical parameters could be extracted. This is especially meaningful in the postfabrication process.

Real-time fuzzy digital filters (RTFDF) properties for siso systems

This paper describes real-time fuzzy digital filter (RTFDF) concepts considering a description of fuzzy logic and adaptive digital filter concepts with real-time properties: the basic characteristic operation of this kind of filters is known as operation regions, knowing it as linguistic natural descriptions.

Application of real time digital filters in NMR spectroscopy

AbstractSince the introduction of Fourier transform NMR spectroscopy, free induction decay (FID) has been available in a binary format, which is required to apply several mathematical treatments on the raw data. Those mathematical procedures are the application of window functions on the FID, baseline correction of the time domain data, and finally the Fourier transformation. Nevertheless, it took a long time until digital filtering was applied on NMR raw data. Digital filtering can be done as either a postprocessing procedure or on the fly. The on the fly concept is preferable, but it requires specialized and very fast processors. With the common availability of such processors, called digital signal processors (DSP), digital filtering on NMR raw data became a routine method. The application of digital filters allows us to overcome problems such as baseline distortion in the NMR spectrum due to nonperfect phase response of any common analog antialiasing filter, distortion of the signal amplitude due to a nonperfect amplitude response of any common analog antialiasing filter, a limited dynamic range due to aliased noise by nonoversampling techniques, reduced dynamic range due to quantization noise, and folded signals due to folded signals outside of the spectral window. The manner in which digital filters are used in a NMR spectrometer is the same as audio applications; it just requires stronger processors to apply high‐performance digital filters on the fly. This article is an introduction to the concept of digital filters. Therefore, the description is strongly simplified and the ideal case is assumed. © 2002 Wiley Periodicals, Inc. Concepts in Magnetic Resonance (Magn Reson Engineering) 15: 164–176, 2002

What is a filter and how to use it

Abstract This paper is a tutortial on the concept of digital filters which are of increasing importance to surveyors using the Global Positioning System, automated theodolites and offshore equipment.

DIGITAL FILTERS IN AUDITORY PHYSIOLOGY

ABSTRACT In auditory research, the manipulation of signals by filtering with analog electronic filters plays an important role. Recently, digital filters that compute signal modifications in realtime became available. They can mimic all functions of analog filters, and additionally make possible new experimental concepts. This tutorial paper introduces the concept of digital filters by using analogies from acoustics. Even complex acoustical environments can be simulated with digital filters, as they allow the programming of almost arbitrary frequency and phase responses.

POLE‐AND‐ZERO DESIGN OF DIGITAL FILTERS

A recent paper in Geophysics by Shanks (1967) provides an excellent introduction to recursive or feedback digital filters. These filters do not appear to have been widely used in geophysics; for example, a recent review paper on the use of digital filters in geophysics (Kertz, 1965) does not mention them. The topic takes on added interest with the recent appearance of several papers following the original paper of Dean (1958), applying digital filter concepts to the analysis of gravity and magnetic data.