Butterworth filter

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

Seventh-order elliptic video filter with 0.1 dB pass band ripple employing CMOS CDTAs

Abstract: In this paper, a CMOS realization of the current differencing transconductance amplifier (CDTA) is given, which is a newly reported active building block for current-mode signal processing. Current differencing stage of the CDTA element is realized using a differential current-controlled current source and in the output stage, floating current sources are used to convert intermediate voltage of z terminal to output currents. Due to the compactness of the circuit, it is capable of high-frequency operation and suitable for video signal-processing applications. The CDTA element is used in a current-mode anti-aliasing video filter, which is designed using operational simulation of a seventh-order passive elliptic filter, so the resulting active filter has the low sensitivity feature of its passive counterpart. The filter has 0.1 dB maximum pass band ripple as imposed by ITU video anti-aliasing filter standard. SPICE-simulation results of both the CDTA element and the seventh-order elliptic filter are given. Simulation results are found in close agreement with theoretical results.

Kolmogorov–Zurbenko filters

Abstract: We reviewed the properties of the Kolmogorov–Zurbenko (KZ) filter and its extensions with applications in high resolution signal and image processing. The KZ filter is defined as an iteration of a moving average (MA) filter. The impulse response function of the KZ filter is a convolution of the rectangular window being used in a MA filter. Zero derivatives at the edges of the impulse response function make it a sharply declining function, providing high frequency resolution. The KZ Fourier transform (KZFT) is derived from the KZ filter by applying it to Fourier transform. Extensions of the KZ filter and the KZFT are demonstrated with examples. Copyright © 2010 John Wiley & Sons, Inc. For further resources related to this article, please visit the WIREs website.

Coupled-Inductor Filter: A Basic Filter Building Block

Abstract: Coupled-magnetics and coupled-inductor filters provide smoothing in a power converter by steering ripple current away from the “quite port.” While this concept is not new, topologies claiming to be “new” or “novel” continue to be reported in the literature, suggesting that the ripple-steering phenomenon may not be well understood to be a property of the filter block itself. This paper describes a general coupled-inductor filter block and presents a brief history of its application starting with the earliest known version of the circuit, which dates back to a 1923 patent application. The coupled-inductor circuit model is reviewed, starting with the basic topology and ideal circuit elements. Real circuit elements are then considered along with the effects of equivalent series resistance and other parasitic elements. A circuit-based filtering approach is used to emphasize the filtering aspect of the coupled inductor. It will be seen that the coupled-inductor filter can exhibit a low pass with notch frequency response. This provides the ability to achieve extra attenuation at a particular frequency, such as the converter switching frequency, which can reduce the overall filtering burden without adding extra inductive components. When the filter components are treated as a functional circuit group, instead of an interconnection of inductors and capacitors, the coupled-inductor filter can be analyzed as a drop-in replacement wherever a smoothing choke would normally be used and does not depend on converter voltage waveforms. A topology transformation of the Cuk converter shows that “zero ripple” in not a special property of the topology, but can be achieved using the coupled-inductor filter block.

Dual-Band Filter Design With Flexible Passband Frequency and Bandwidth Selections

Abstract: In this paper, improved dual-band filter design is studied. The dual-band resonators are composed of shunt open- and short-circuited stubs. In order to fulfil the requirements of dual-band inverters, a structure of stepped-impedance asymmetric coupled lines is proposed and its equivalent circuit is also derived. The dual-band filter is then designed based on this equivalent circuit. This type of filter can achieve relatively large practical passband center frequency ratios (in theory infinite), and it has more freedom of bandwidth ratio. The circuit size is also reduced. Detailed design procedure is presented and, finally, a filter example is given to validate the theoretical study

Universal filter using two current-feedback amplifiers

Abstract: A new universal filter using two current-feedback amplifiers is presented. This filter can realise lowpass, bandpass, highpass, notch and allpass filters from the same configuration. It has the following features: orthogonal control of the natural frequency and quality factor by grounded resistors, easy conversion into a voltage-controlled filter, minimum active components, without match components except for allpass applications, low active and passive sensitivities, and cascadability. Experimental results that confirm the theoretical analyses are obtained.