Butterworth filter

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

Nth-root Stack Nonlinear Multichannel Filter

Abstract: A nonlinear multichannel filter is developed which appears to be particularly useful for enhancement of seismic refraction and teleseismic array data The basic filter involves the extraction of the Nth root of each element in the matrix forming the data set, where N is any positive integer, and the Nth power of the summation over the channels The filter is effective in reducing random noise, whereas identical signals which are in-phase on all channels are retained at the expense of some distortion The output from this nonlinear filter has far greater resolution in specifying phase velocity than any multichannel linear filter we have employed Examples of theoretical and actual field seismograms are presented after various forms of filtering to illustrate their effectiveness

A Frequency Selective Filter for Short-Length Time Series

Abstract: An effective and easy-to-implement frequency filter is proposed, obtained by convolving a raised-cosine window with the ideal rectangular filter response function. Three other filters, Hodrick--Prescott, Baxter--King, and Christiano--Fitzgerald, are thoroughly reviewed. A bandpass version of the Hodrick--Prescott filter is also introduced and used. The behavior of the windowed filter is compared to the others through their frequency responses and by applying them to both quarterly and monthly artificial, known-structure series and real macroeconomic data. The windowed filter has almost no leakage and is better than the others at eliminating high-frequency components. Its response in the passband is significantly flatter, and its behavior at low frequencies ensures a better removal of undesired long-term components. These improvements are particularly evident when working with short-length time series, which are common in macroeconomics. The proposed filter is stationary and symmetric, therefore, it induces no phase-shift. It uses all the information contained in the input data and stationarizes series integrated up to order two. It thus proves to be a good candidate for extracting frequency-defined series components.

Systematic Method for the Exact Synthesis of Ultra-Wideband Filtering Responses Using High-Pass and Low-Pass Sections

Abstract: A systematic consistent and analytical method for the exact synthesis of ultra-wideband bandpass filtering responses using the isolated cascade connection of high- and low-pass sections is presented in this paper. Through the described synthesis technique, the optimum values for the design parameters of the high- and low-pass sections are computed from the initial specifications of the intended bandpass filtering profile. The theoretical results are validated with a synthesis example for both the Butterworth and Chebyshev cases. Furthermore, to prove the practical viability of the ultra-wideband filter topology based on high- and low-pass sections, a prototype at 4 GHz is designed, constructed in hybrid technology, and characterized. The main advantages of this wideband microwave bandpass filter solution are also highlighted

Microwave photonic filter with single bandpass response

Abstract: A new microwave photonic filter that solves the problem of realising a single bandpass RF response is presented. The filter is based on using phase modulation together with a pair of gratings, and eliminates the baseband response and periodic spectral response of typical FIR filters. Experimental results demonstrate a single passband square-type bandpass filter response, and operation to high frequencies.

A comb filter design using fractional-sample delay

Abstract: In this paper, a new comb filter design method using fractional sample delay is presented. First, the specification of the comb filter design is transformed into that of fractional delay filter design. Then, conventional finite impulse response (FIR) and allpass filter design techniques are directly applied to design fractional delay filter with transformed specification. Next, we develop a constrained fractional delay filter design approach to improve the performance of the direct design method. Finally, several design examples and an experiment of power line interference removal in an electrocardiogram (ECG) signal is demonstrated to illustrate the effectiveness of this new design approach.