Butterworth filter

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

Digital-to-analog conversion by pulse-count modulation methods

Abstract: Three low-cost digital-to-analog converters (DACs) are described and compared. These designs can easily be implemented in an integrated circuit: the conventional pulse-width modulation (PWM) DAC, the new pulse-count modulation (PCM) DAC and the first-order noise shaping (FONS) DAC. All three methods control the ratio of the sum of all pulse durations to the constant total period. As the pulse durations are integral multiples of a unit pulse, all three can be classified as pulse-count modulation methods. Block diagrams of all three DACs consisting of a simple digital circuit and a low-pass filter are presented. For a constant digital input value the worst case ripple of the filter output is used to calculate the cutoff frequency of the low-pass filter. Approximations for the 3 dB cutoff frequency of first-order, second-order and fourth-order Butterworth low-pass filters are given. The dynamic properties are analyzed in the time domain (settling time) and in the frequency domain (unfiltered output spectrum of a full-scale sine wave input). The main influences on the static accuracy are analyzed. A case study demonstrates the abilities of PCM and FONS.

Microwave Voltage-Controlled Oscillator With Harmonic-Suppressed Stepped-Impedance-Resonator Filter

Abstract: This brief proposes a new low-phase-noise microwave voltage-controlled oscillator (VCO) with a harmonic-suppressed stepped-impedance-resonator (SIR) filter. Since the filter is synthesized by multiple resonators, it can provide a high-quality factor to improve the phase-noise performance. In addition, the harmonic-suppressed property of the filter adopted in this brief can alleviate the noise contributed from the oscillation harmonics. By applying the two techniques mentioned, the proposed VCO is designed at 2.4 GHz with a three-pole Butterworth filter, which is synthesized by the parallel transmission-line SIRs to reduce the circuit size. The proposed VCO using a three-pole filter has a measured phase noise of −147 dBc/Hz at 1-MHz offset frequency with a corresponding figure-of-merit of −203.18 dBc/Hz.

A 3V 12-55MHz BiCMOS Continuous-Time Filter with Pseudo-Differential Structure

Abstract: In this paper a 3V 2nd order lowpass continuous-time filter is presented. The filter is based on a highly linear pseudo-differential transconductor. The input common-mode signal is cancelled at the transconductor level using a feed-forward path. The output common-mode voltage is controlled at the filter level using lossy-integrators. A prototype cell has been realized in 1.2?BiCMOS technology. The pole frequency can be tuned in the range 12-55MHz. A THD of ?40dB is achieved for signals up to lVpp at 10MHz. The dynamic range is approximately 60dB.

An Active-RC Complex Filter with Mixed Signal Tuning System for Low-IF Receiver

Abstract: An active-RC complex filter synthesized from leapfrog low-pass prototype is proposed in this paper, which is less sensitive to components values variation comparing with the common used cascade-pole method. Furthermore, a mixed-signal tuning system was implemented to make the RC time constant stable, and can be turned off after the completion of tuning. The filter was implemented in 0.18mum CMOS process. It is centered at 4MHz with 2MHz of bandwidth. It has the voltage gain of about -2dB, the image rejection ratio of about 28dB, the output 1-dB compression voltage of 0.39V, the in-band integral output noise of 32muVrms, and the power consumption of 6.1mW. The filter can be used in the low-IF GPS receiver

Vehicular active vibratory noise control apparatus

Abstract: A subtractor subtracts a first control signal output from a first bandpass filter from an error signal, and supplies a differential signal to a second bandpass filter. The second bandpass filter, which has a central frequency of 70 Hz, is affected by an operation of the first bandpass filter, i.e., a first control signal, which has a central frequency of 40 Hz. The first bandpass filter is not affected by an operation of the second bandpass filter, i.e., the second control signal.