Butterworth filter

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

Compact microstrip dual-mode dual-band bandpass filter with wide stopband

Abstract: A compact microstrip dual-mode dual-band bandpass filter is presented. The filter consists of two E-shaped resonators and two T-shaped feedlines. By utilising the odd-mode and even-mode resonance properties of the proposed E-shaped resonator, the new filter is designed with two transmission poles in both passbands. Furthermore, the introduced two T-shaped feedlines and a coupling between them can result in multi-transmission zeros in the stopband, which will improve the selectivity of the filter. To validate the design theory, a dual-mode dual-band filter with two passbands located at the centre frequencies of 1.8 and 2.4 GHz, respectively, were designed and fabricated. Both experimental and simulation results are provided, with good agreement.

Generalization of the linear matched filter concept to nonlinear matched filters

Abstract: A nonlinear matched filter based image correlator is investigated. The linear matched filter is expressed as a bandpass function containing the amplitude and phase of the Fourier transform of the reference signal. The bandpass filter function is then applied to a kth law nonlinear device to produce the nonlinear matched filter function. Analytical expressions for the nonlinear matched filter are provided. The effects of the nonlinear transfer characteristics on the correlation signals at the output plane are investigated. The correlation signals are determined in terms of the nonlinear characteristics used to transform the filter. We show that the nonlinear filter results in a sum of infinite harmonic terms. Each harmonic term is envelope modulated due to the nonlinear characteristics of the device, and phase modulated by m times the phase modulation of the linear filter function. The correct phase information of the filter is recovered for the first-order harmonic of the series. The envelope of each harmonic term is proportional to the kth power of the Fourier transform magnitude of the reference signal. We show that various types of filter such as the continuous phase-only filters can be produced simply by varying the severity of the nonlinearity. Nonlinear filters provide higher correlation peak intensity and a better defined correlation spot.

A /spl plusmn/1.5-V, 4-MHz CMOS continuous-time filter with a single-integrator based tuning

Abstract: A 4-MHz, fifth-order elliptic low-pass Gm-C filter is described whose characteristics are tuned by an on-chip automatic tuning circuit. The tuning circuit uses only one integrator as the master of tuning instead of problematic voltage controlled oscillator (VCO) and voltage controlled filter (VCF). MOS transistors in linear operation region perform the voltage-to-current conversion in an operational transconductance amplifier, and thereby we achieved /spl plusmn/1.5 V operation. A prototype filter was implemented in a 0.8-/spl mu/m double-poly, double-metal CMOS process. The filter exhibits the dynamic range of 57.6 dB and dissipates 10 mW with /spl plusmn/1.5-V supply. The stopband attenuation is better than 45.0 dB and the passband ripple is smaller than 1.0 dB.

Transversal filter for use in a digital subscriber line transmission interface

Abstract: A transversal filter has a transfer function for which a zero point occurs outside a unit circle on z plane and thus the output waveform has a ringing characteristic having a change from negative to positive around a precursor and before a main cursor and is associated and integrated with another transversal filter, thereby forming a waveform shaping decimation filter or a pulse shaping high-pass filter. The waveform decimation filter can eliminate a high frequency noise, changes a high frequency input data to a low frequency output data, and performs a waveform shaping operation. Therefore it cannot require a pulse shaping filter separated from the decimation filter. The pulse shaping high-pass filter includes a pulse shaping filter whose number of the taps is decreased and performs high-pass filter function. A pulse shaping filter whose number of the taps is decreased can be used separately from the high-pass filter.