Butterworth filter

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

IIR filter design via optimal Hankel-norm approximation

Abstract: A new technique for digital filter design is presented. Based on the singular value decomposition of the Hankel matrix, balanced realisation and all-pass functions, an IIR filter is obtained via an optimal Hankel–norm approximation. The error between the optimal filter with order r and the desired filter is found to be equal to the (r + l)th singular value of the Hankel matrices. The designed low-pass filter and the differentiator are given to illustrate the proposed design algorithm.

Microwave reflection filter including a ladder network of resonators having progressively smaller Q values

Abstract: A variable Q reflection mode filter has a three-port circulator, one port of which is terminated by a one-port filter. The filter includes a ladder network of resonators, successive of the resonators having progressively reducing Q values. The filter increases the overall 3 dB resonance point of the filter to reduce the unloaded Q factors required for particular applications. The filter may be arranged to provide a maximally flat response, an equiripple response, or a quasi-ripple response. Transmission zeros may also be incorporated to further enhance the effective unloaded Q.

Optimum processing protocols for volume determination of the liver and spleen from SPECT imaging with technetium-99m sulfur colloid.

Abstract: A study of the effects of processing parameters on the determination of liver and spleen volume from SPECT data was performed A method for volume determination using a threshold algorithm was calibrated against phantoms and applied to 60 patient studies Good reproducibility was found using different projections and computing the volume on separate days Variations of the measured volumes with the threshold value, reconstruction filter cutoff frequency and attenuation correction were investigated Reconstruction parameters producing best image quality were also determined A threshold of 25% of the maximum value in the organ was determined from phantom studies Changes of 1% around this value yielded changes of 2–3% in the computed volume No significant change was noted as cutoff frequencies varied between 04 and 085 of Nyquist(0031 to 0066 cycles/cm)for a third order Butterworth filter Attenuation correction produced a decrease of 9% and 6% in liver and spleen measured volume respectively Best image quality was obtained with 04 Nyquist (0031 cycles/cm)cutoff frequency for third order Butterworth filter and attenuation correction It is concluded that optimal parameters must be determined for any processing protocol, and must then be adhered to in future applications to insure clinical accuracy, especially those parameters demonstrating the most quantitative and qualitative sensitivity

Second Order Low-Pass and High-Pass Filter Designs Using Method of Synthetic Immitance Elements

Abstract: The paper briefly describes the basics of frequency filter design method using synthetic immittance elements with current conveyors. An introduction of the paper explains the advantages and also disadvantages of using this method. Other chapters briefly introduce a design process of simple second order low-pass and high-pass filter. A theory of current conveyors is discussed too, because they are the basic building blocs of proposed synthetic element and also active frequency filters. Finally, the particular solutions of low-pass and high-pass filters are given and verified by OrCAD PSpice simulations.