Butterworth filter

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

A Compact Dual-band Bandstop Filter Based on Fractal Microstrip Resonators

Abstract: Fractal geometries are found attractive to designers seeking for compact size microwave circuits and antennas. In this paper, Peano fractal based open-loop resonators are adopted to design dual-band microstrip band-stop filters (PSFs). The suggested filter structure is essentially based on that of the conventional open-loop rectangular microstrip resonators. The resonators of the proposed PSF structure are made in the form of Peano fractal geometry with different iteration levels. Many filters have been modeled, and their performances have been evaluated using a commercially available full-wave electromagnetic simulator. Each of the modeled filter structures contains two pairs of open loop fractal based resonators with different iteration levels. The lower frequency band-stop performance is attributed to the resonators with higher iteration level while the higher frequency band-stop performance is due to the resonators with lower iteration level. Simulation results for the proposed microstrip filters have confirmed the validity to realize compact dual-band narrow-stopband microstrip filters. A comparative study implies that higher size reduction of the realized filter has taken place as the iteration level of the fractal microstrip open-loop resonators becomes higher. The results presented show that the fractal-based resonators can be used to construct compact narrow-stopband filters suitable for a wide variety of the recently available communication applications.

Design flexibility of an open-loop resonator filter using similarity transformation of coupling matrix

Abstract: In this letter, the design flexibility of an elliptic-response open-loop resonator filter is achieved through similarity transformation of the coupling matrix. To verify the proposed method, a compact four-pole elliptic-response bandpass filter is designed using the conventional structure with open-loop resonators. Designed filter has the resonators with very narrow spacing for the required coupling coefficient and it is impossible to implement a filter with wider fractional bandwidth. Two possible configurations to overcome this problem are presented through similarity transformation of the coupling matrix. From this design flexibility, a filter with wider fractional bandwidth is designed with realizable design parameters.

Through-support-coupled micromechanical filter array

Abstract: This paper presents a new concept for implementing high-order mechanically-coupled ultra-small bandwidth micro-mechanical filter arrays without using discrete coupling elements. Adjacent resonators are coupled by elastic deformation at the support, and filter bandwidth is defined by the spacing between resonating elements. We demonstrate a second-order through-support-coupled capacitively-transduced 1.72MHz 0.008%BW (/spl Qscr/;/sub filter//spl ap/12000) bandpass flexural-mode beam filter array implemented on SOI. The coupling concept and experimental results were verified with finite element analysis using ANSYS. This integrated coupling technique does not introduce additional fabrication requirements for a discrete mechanical coupling element and therefore has strong potential for application to high-order higher frequency filter arrays. Resonator fine tuning is shown to be essential for obtaining ultra-small coupling-limited filter bandwidths.

Finite impulse response (FIR) filter compiler

Abstract: A method, apparatus and system for building a filter is disclosed. In a particular embodiment, the filter is a finite impulse response (FIR) filter and a compiler suitable for implementing the FIR filter is described. The compiler includes a filter coefficient generator suitably arranged to provide a first set of filter coefficients corresponding to the desired FIR filter spectral response and a filter spectral response analyzer coupled to the filter coefficient generator for providing an expected FIR filter spectral response based in part upon the first set of filter coefficients. The compiler also includes a filter resource estimator coupled to the filter spectral response simulator for estimating an implementation cost of the FIR filter based upon the second set of filter coefficients as well as a filter compiler unit coupled to the resource estimator arranged to compile a FIR filter implementation output file.

Determination of the optimum filter for qualitative and quantitative 99mTc myocardial SPECT imaging

Abstract: *Corresponding author: Muhammad Nur Salihin Yusoff, Medical Radiation Programme, School of Health Science, University Science Malaysia, 16150 Kubang Kerian, Kelantan, Malaysia. E-mail: mnsalihin@gmail.com Background: Butterworth, Gaussian, Hamming, Hanning, and Parzen are commonly used SPECT filters during filtered back-projection (FBP) reconstruction, which greatly affect the quality and size accuracy of image. Materials and Methods: This study involved a cardiac phantom in which 1.10 cm thick cold defect was inserted into its myocardium wall and filled with 4.0 μCi/ml (0.148 MBq/ml) 99mTc concentration. The cardiac insert was then put into a cylindrical tank which was filled with 1.2 μCi/ml (0.044 MBq/ml) 99mTc concentration as background. 272 combinations of filter parameters were selected from those filters and applied on image. The measurements of count in myocardium, background, and defect regions of interest (ROI) were performed on each filtered image. Those measurements were then used to calculate contrast, signal-to-noise ratio (SNR), and defect size. For every filter, each criterion was graded (1 to 100) and then summed at their specific setting for total comparison. Results: The results show that, the different filter types produced myocardial image with different contrast, SNR, and defect size. For contrast and SNR, Gaussian filter was the best, while Parzen filter was the best in producing accurate defect size. However, Butterworth filter was found the best for trade off between contrast, SNR, and defect size accuracy. Conclusion: Selection of filter should consider the type of analysis, whether qualitatively or quantitatively. Qualitative analysis depends on image quality which is denoted by high contrast and SNR, thus Gaussian filter was suggested. Instead, the Butterworth filter was suggested for quantitative analysis as it is greatly dependent on both, image quality and size accuracy. Iran. J. Radiat. Res., 2009; 6 (4): 173­182