Band-pass Filtering Technique Research Articles

Evolving Post-World War II UK Economic Performance

This paper uses tests for multiple structural breaks at unknown points in the sample period, and band-pass filtering techniques, to investigate changes in UK economic performance since the end of World War II. Empirical evidence suggests that the most recent decade, associated with the introduction of an inflation-targeting regime, has been significantly more stable than the previous post-WWII era. For real GDP growth, and for three measures of inflation, break dates are identified at around the time of the introduction of inflation-targeting, in October 1992. For all four series, the estimated innovation variance over the most recent subperiod has been the lowest of the post-WWII era. The volatility of the band-pass filtered macroeconomic indicators considered has been, after 1992, almost always lower than either during the Bretton Woods regime or the 1971-92 period; often, as in the cases of inflation and real GDP, markedly so. The Phillips correlation appears to have undergone significant changes over the past 50 years, from being unstable in the 1970s, to slowly stabilising from the beginning of the 1980s onwards. After 1992, the correlation has exhibited by far the greatest degree of stability during the post-WWII era.

Detecting Defects in Textile Products Based on Band-pass Filtering Techniques

Two dimensional band-pass filters can be used to enhance the edges of the defects contained in fabric images. In this paper, we designed two types of 2D band-pass filters for the automatic detection of defects. One is the matched Gabor filter, and the other is the matched Mexican hat wavelet. Experiments show that the matched Gabor filter is more suitable for defects of higher frequency, while the matched Mexican hat wavelet is more effective for defects of lower frequency. Based on the two types of band-pass filters, an automatic fabric defect detection system was designed which boasts good accuracy and high speed.

Evolving Post-World War II U.K. Economic Performance

In this paper we use tests for multiple structural breaks at unknown points in the sample, and band-pass filtering techniques, to investigate changes in U.K. economic performance since the end of World War II. Empirical evidence suggests that the most recent decade, associated with the introduction of an inflation targeting regime, has been significantly more stable than the previous post-WWII era. Both for real GDP growth, and for three measures of inflation, we identify break dates around the time of the introduction of inflation targeting, in October 1992. For all four series, the estimated innovation variance over the most recent sub-period is the lowest of the post-WWII era. The volatility of the band-pass filtered macroeconomic indicators we consider is, after 1992, almost always lower than either during the Bretton Woods regime, or over the 1971-92 period, often, like in the case of inflation and real GDP, markedly so. The Phillips correlation appears to have undergone significant changes over the last 50 years, from being unstable in the 1970s, to slowly stabilising from the beginning of the 1980s onwards. After 1992, the correlation exhibits, by far, the greatest extent of stability of the post-WWII era.

Classical tidal harmonic analysis including error estimates in MATLAB using T_TIDE

A standard part of any oceanic pressure gauge or current meter analysis is the separation of tidal from non-tidal components of the signal. The tidal signal can either be discarded, or its characteristics described in some fashion useful for further analysis. Although tidal signals can be removed by standard high or bandpass filtering techniques, their relatively deterministic character and large amplitude make special techniques more effective. In classical harmonic analysis, the tidal signal is modelled as the sum of a finite set of sinusoids at specific frequencies related to astronomical parameters. A set of programs has been written in MATLAB to (a) perform classical harmonic analysis for periods of about 1 year or shorter, (b) account for (some) unresolved constituents using nodal corrections, and (c) compute confidence intervals for the analyzed components.

Geophysical Applications of Multidimensional Filtering with Wavelets

We present imaging results in geophysics based on using multidimensional Gaussian wavelets as a filter in a 2-D Cartesian domain. Besides decomposing the field into various distinct lengthscales, we have also constructed the 2-D maps describing the spatial distributions of the maximum of the wavelet-transformed L2-norm Emax (x,y) and its corresponding local wavenumber k max (x,y),where x and y are the Cartesian coordinates. For geoid anomalies, using a wavelet filter extending to 90 degrees, we have discerned the distinct outlines of convergent and divergent tectonic zones and have conducted a quantitative comparison of the short-wavelength gravitational anomalies at those wavelengths between two different geographical locations. We have also compared the wavelet results with a nonlinear bandpass filter in the spectral domain where a Gaussian filter with the logarithm of the degree/acting as the argument has been employed. A wavelet solution, with a length-scale corresponding to 256 degrees, would need a filter with over 400 spherical harmonics centering around l = 157 for an optimal spatial fit. The computational effort with the bandpass filter technique greatly exceeds those associated with wavelets. We have also shown the ability of the wavelets to analyze the vastly different scales present in high Rayleigh number convection and the mixing of passive heterogeneities driven by thermal convection. Wavelets will be a useful tool for rapid analyzing of the large multidimensional fields to be captured in many other geophysical endeavors, such as the upcoming gravity satellite missions and satellite radar interferometry images.

Multilayer ceramic bandpass filter at microwave frequency

This paper describes an accurate design technique for multilayer bandpass filters for wireless communication system applications. Using coupled strip-line and J-inverter theories, the filters were analyzed and designed in a multilayer structure. The designed structures were simulated using MDS and IE3D simulators. Fabricated filters were measured by an HP8757D network analyzer. Sample results of the filter performances demonstrate excellent potential of the multilayer structure. It indicates that the filter can have a response that is in good agreement with the simulation result without a cofiring process. ©2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 24: 258–260, 2000.

Length measurement by a two-colour interferometer using two close wavelengths to reduce errors caused by air turbulence

An improved two-colour interferometer for length measurements was developed to reduce both the errors caused by air turbulence and the effects of chromatic aberration in the optical system. The method combines a fringe-counting technique and a phase-measurement technique. The phases of interference fringes with respect to laser wavelength 1 and synthetic wavelength s are detected simultaneously by only one detector by using a band-pass filter technique. We verified this new method by measuring lengths of up to 2 m and then comparing the results with those measured by an HP 5528 interferometer. The comparison shows that the relative accuracy of this improved method is 5 × 10-7.

Optimal band pass filtering of transient evoked otoacoustic emissions in neonates.

This paper investigated the performance of an optimal bandpass filtering technique to effectively identify click evoked otoacoustic emissions in neonates. The frequency response of the filter was optimized by maximizing the correlation coefficient between two replicate recordings (reproducibility). The optimal cut-off frequencies were also set by controlling the maximum energy loss after filtering to stop the crucial response contents being filtered along with the noise. As an additional constraint, the cut-off frequencies were forced to be outside the range of 1.6 to 4.2 kHz to avoid (in a response identification task) the spontaneous otoacoustic emissions from polarizing the cut-offs and thereby filtering fundamental frequency components, thus leading to an erroneous response classification. The best performance of the optimal filter in terms of increasing the post-filtering reproducibility was obtained when the procedure was applied to recordings whose reproducibility before filtering ranged between 60 and 80 per cent, i.e. for responses classified in most cases as partial pass.

Optimized E-plane bandpass filters with improved stopband performance

A computer-aided synthesis technique for E-plane bandpass filters with improved stopband performance is developed. An optimization procedure based on equal ripple optimization is adopted. The design of a symmetrical E-plane bandpass filter with improved stopband performance is considered; higher order mode interaction between E-plane discontinuities is included in the design. The predicted filter performance shows improved stopband performance and reduced filter dimensions compared with conventional E-plane bandpass filters. The validity of the method is confirmed by the measurement of a fabricated five resonator E-plane bandpass filter with improved stopband performance.

Quantification of Predictive Skill for Mesoscale and Synoptic-Scale Meteorological Features as a Function of Horizontal Grid Resolution

Abstract To quantitatively assess numerical predictive skill for synoptic and mesoscale features as a function of horizontal grid resolution, a series of experiments is conducted using the Pennsylvania State University-National Center for Atmospheric Research Mesoscale Model. For eight cases of continental cyclogenesis, 72-h integrations are examined using grids of 160, 80, and 26.7 km. First, we briefly examine error statistics for synoptic-scale cyclones and anticyclones. Next, a detailed analysis of model errors for mesoscale features is presented. A bandpass filtering technique, based on the Barnes objective analysis scheme, is used to separate perturbation quantities associated with the mesoscale features from the synoptic-scale fields. Error statistics are then compiled for various mesoscale features, including the intensity of mesolows, damming ridges, and postfrontal troughs, and the thermal gradients, propagation speed, and vertical velocity maxima associated with surface cold fronts. Finally, th...

Isolated Word Recognition System using 68000 Microprocessor

This paper describes the design of a simple, inexpensive speech recognition system using simple hardware and a highly powerful Motorola's 68000 microprocessor. The system is speaker dependent and works with a vocabulary of 30 words with an accuracy of around 90%. The system is developed using band pass filtering technique for feature extraction and linear time normalization for data compression. Euclidean distance measurement is used for distance calculation. The system can be trained easily for a new speaker. Because of its simplicity, it can be developed as a prototype in colleges for demonstration.

Transform edge detection

The blockwise transform edge detection method consists of segmenting the image into a number of small blocks, with neighboring blocks overlapping slightly; transforming each block by a fast transform; multiplying the transform coefficients of each block by a bandpass mask; inverse transforming the modified transform coefficients; detecting zero crossings and deciding an edge according to a thresholding scheme. Simulation results with the blockwise transform edge detection method in comparison to other bandpass filtering techniques indicate that higher performance is achieved with the new technique on the average. This is believed to result from the use of blockwise generalized filtering with appropriate transforms rather than linear convolutional filtering, as in other bandpass filtering techniques. The new method also has less computational complexity, and is well-suited to parallel processing.

Conventional PD measurement techniques used for complex HV apparatus

The aim of conventional potential discharge (PD) measuring techniques is the quantification of an apparent charge q, which is, in general, provided by band-pass filter techniques. However, as the capability of a filter to integrate signals and its 'pulse resolution time' are strongly interlinked with the band-pass characteristics of the filters, the design of conventional PD measuring circuits appears quite arbitrary. The authors discuss, therefore, some deficiencies of the Standards, which are inadequate for designing standardized PD instruments. The interaction between band-pass filter parameters and pulse resolution as defined in IEC Standard 270 is investigated. A complete PD testing and measuring circuit for GIS components is simulated and shows the difficulties in applying conventional PD measuring circuits to such complex systems.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Solar Cycle Graphics 1700–1988 AD

AbstractA graphical format has been adopted to depict some characteristic variations associated with the solar activity cycle up to 1988, for both the Zurich annual and monthly mean values over the respective periods from 1700 and 1750. Both low pass and band pass filtering techniques have been employed to smooth the data, the autocorrelation coefficients determined for a high number of lags to illustrate the secular modulation of the maximum values in each cycle and the spectral amplitudes computed to establish periodicities in the chronologies.

Australian Tree Ring Chronologies as Proxy Data for Solar Variability

AbstractData from the Solar Maximum Mission satellite suggests that there is a 0.1 percent variation in solar luminosity over the 11-year solar cycle with maximum output corresponding to maximum sunspot number. Tree ring chronologies can be utilized as proxy data to compile a record of the magnitude of past solar variability. Spectral analysis of tree ring series compiled from a site in Tasmania has established, among others, significant periodicities of about 90 and 11 years. The application of band pass filter techniques shows that the 11-year cycle present in some tree ring series correlates with the Zurich sunspot numbers over the period from AD1700, the extent of accurate sunspot records, with a time lag of about three years.

A SAW bandpass filter technique using a fanned multistrip coupler

A SAW filter is described which uses multistrip couplers with diferent periodicities in two adjacent tracks in order to transfer a surface wave from one track to the other over a restricted frequency band, i.e., to filter the signal. The principal advantage is good filtering with low insertion loss. Over 30-dB out-of-band rejection with 3-dB loss in the fanned multistrip coupler at a frequency of 216 MHz is demonstrated.

Surface Elastic Wave Bandpass Filters for Frequency Synthesis (Short Papers)

Surface elastic wave bandpass filter techniques have been applied to the development of a minaturized frequency synthesizer for satellite communications systems. A bandpass filter centered at 247 MHz has been developed exhibiting less than 7-dB insertion loss over a 6-MHz 1-dB band, with sidelobe rejection greater than 45 dB.

Velocity and Q of mantle waves

Phase velocity and Q of long-period waves have been determined for 13 great-circle paths for Rayleigh waves and 12 great-circle paths for Love waves. Group velocities are also determined by band-pass filtering technique. Some of the preexisting data are incorporated to obtain representative sets of data for Q, phase and group velocities. With these sets of data stringent tests of various Earth models are possible. Each great-circle path is divided into oceanic, “tectonic” and shield portions, and a regression analysis is made on the phase velocity data to obtain pure-path dispersion curves for these distinct tectonic provinces. For both Love and Rayleigh waves, the pure-path phase velocity is found to be significantly lower for tectonically active regions than for ocean and shield. This difference in the phase velocity curve suggests that the mantle structure beneath tectonically active regions is significantly different from that elsewhere even at depths below 200 km.

Octave Bandwidth Tunnel-Diode Amplifier

Two tunnel-diode amplifiers for the frequency ranges 2 to 3 Gc and 3 to 4 Gc are combined with hybrids and low-pass filters to provide an octave bandwidth amplifier. The amplifier design is based on band-pass filter techniques. The gain exceeds 10 db over this band with noise figure better than 4 db.

A band-pass filter technique for recording atmospheric turbulence

A description is given of multi-band electrical filters and associated circuits which can be used to simulate numerical methods of computing the magnitude of eddy velocity. The filters are supplied directly with the voltage from a wind sensor, and outputs from the filters are recorded as mean deviations. These are then converted to standard deviations by multiplying by a `form factor'. Evidence of the consistency of the form factor is presented. The equipment may also be used to obtain in `real time' a measure of the power or energy spectrum of wind gusts from a frequency of about 1 cycle per hour up to the cut-off frequency of the sensor.