Butterworth filter

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

High pass switched capacitor filter section

Abstract: A high-pass switched capacitor biquadratic filter based on the bilinear z-transform The filter comprises first and second integrating operational amplifiers connected in series and in combination with a third operational amplifier that serves as a sample and hold and also generates one simple pole and zero pair in the circuit transfer function thereby enabling the circuit to provide for a high degree of filter efficiency in a preselected frequency range The operational amplifiers are connected to and operate in cooperation with capacitors of a predetermined size which are switched on and off continuously by two phase clock signals supplied to the circuit The loss characteristic of the filter can be programmed by varying the clocking frequency Higher order filters can be obtained by the tandem connection of second order circuit sections followed by one or more first order pole-zero section

Filter which tracks changing frequency of input signal

Abstract: A tracking band-pass filter useful for locking onto, and passing, an input signal which changes rapidly in frequency. The filter has a frequency pass band controlled by a rectangular voltage waveform which is derived from the output signal passed by the filter. The filter output signal is translated from a sine wave to a pulse wave. The period between each two successive pulses is measured by counting the cycles of an oscillator during each respective period. The time-representing count is inverted to a frequency-representing count which controls the duty cycle of a rectangular wave used to make the filter track the changing frequency of the input signal.

Least-mean squares adaptive digital filter havings variable size loop bandwidth

Abstract: An adaptive digital filter uses a weight adjustment unit for adjusting the weights of an adaptive digital filter according to one or more input signals to the digital filter and according to an error signal indicative of the difference between the actual and desired outputs of the digital filter. The weight adjustment unit has a first low-pass filter for low-pass filtering a signal indicative of the product of the error signal and the one or more input signals, a squarer for squaring the output of the first low-pass filter, a second low-pass filter for low-pass filtering the output of the squarer to extract the D.C. component thereof, a third low-pass filter for low-pass filtering a signal indicative of the output of the error signal squared to extract the D.C. component thereof, a dividing unit for dividing the output of the second low-pass filter by the output of the third low-pass filter to provide a loop bandwidth, and a weight calculation unit for providing values for one or more weights of the adaptive digital filter according to the previous values of the weights and the value of the loop bandwidth.

A simple design method for near-perfect-reconstruction nonuniform filter banks

Abstract: In this correspondence, we propose a simple design method for nonuniform integer-decimated filter banks based on a uniform cosine-modulated filter bank. The resulting distortion and aliasing are comparable to the stopband attenuation of the prototype filter. Examples are given to demonstrate the proposed method.