Butterworth filter

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

Digital pre-distortion for the linearization of power amplifiers with asymmetrical characteristics

Abstract: An input signal is pre-distorted to reduce spurious emissions resulting from subsequent signal amplification. Frequency-dependent pre-distortion is preferably implemented in combination with frequency-independent pre-distortion, where the frequency-dependent pre-distortion corresponds to amplifier distortion that has a magnitude that is proportional to the frequency offset from the carrier frequency and a ±90° phase shift on either side of the carrier frequency. The frequency-dependent pre-distortion is generated by differentiating waveforms corresponding to two different sets of pre-distortion parameters with respect to time. In one embodiment, one of the differentiated waveforms is applied to a positive-frequency filter and the other to a negative-frequency filter to generate positive- and negative-frequency pre-distortion signals, respectively, to account for asymmetries in the amplifier characteristics. In another embodiment, only one of the differentiated waveforms is applied to an asymmetric filter (i.e., either a positive-frequency filter or a negative-frequency filter).

Synthesis and Analysis of Electronically Adjustable Fractional-Order Low-Pass Filter

Abstract: A proposal of a fractional (1+α)-order low-pass filter is presented in this paper. The proposed filter operates in the current-mode and it is designed using Multi-Output Current Followers (MO-CFs), Dual-Output Current Follower (DO-CF), Dual-Output Adjustable Current Amplifier (DO-ACA) and Adjustable Current Amplifiers (ACAs) as active elements within the presented topology of the filter. The filter possesses ability to electronically control its order and also the pole frequency by changing the current gain of current amplifiers (ACAs) already present in the structure. Three different values of the order and pole frequency of the proposed low-pass filter were tested as an example. Design of the proposed filter is supported by simulation and experimental results. Simulations of the circuit are carried out in PSPICE simulator with behavioral models of used active elements. The experimental laboratory measurements are performed with the help of available devices forming equivalent circuits. Simulations and experimental results of the electronical control of the order and pole frequency are compared in this contribution.

Partial-Update Schmidt–Kalman Filter

Abstract: The Schmidt–Kalman (or “consider” Kalman filter) has often been used to account for the uncertainty in so-called “nuisance” parameters when they are impactful to filter accuracy and consistency Us

Digital implementation of a new type of hybrid filter with simplified control strategy

Abstract: A new type of hybrid active filter to compensate harmonics of a nonlinear load is presented in this paper. The proposed topology of hybrid filter combines a shunt passive filter (PF) and a shunt active filter (AF). A series inductor between both the filters is introduced to create a harmonic voltage source at the input of nonlinear load. A diode bridge rectifier with R-C load is considered as a nonlinear load. An indirect current controlled voltage source inverter (ICC-VSI) is considered as an AF. A simple control algorithm based on proportional plus integral control of a self-supporting DC bus voltage of the shunt AF is implemented on a TMS320C31 DSP. The passive filter is tuned to compensate 5/sup th/ and 7/sup th/ harmonics, while the AF compensates the rest of harmonics of the load current. A laboratory prototype model of the proposed hybrid filter is developed and its performance is examined. Experimental results are given and discussed.

A simplified analysis for high power microwave bandpass filter structures

Abstract: A method for computing the peak resonator voltages inside a bandpass filter and multiplexer is introduced based on the general cross-coupled lumped element prototype network of a filter. In this method, the resonator voltages are computed based on the circuit model and are shown to be related to the peak filter cavity voltages through an appropriate scale factor. Being circuit theoretical the method is simple and is considerably faster than techniques based on rigorous field theoretic tools. The proposed method is verified using direct calculation of voltages by commercial FEM software. This voltage estimation procedure would considerably simplify multipaction and power handling studies of critical filter based structures.