Topic
Voltage-controlled filter
About: Voltage-controlled filter is a research topic. Over the lifetime, 5514 publications have been published within this topic receiving 70872 citations. The topic is also known as: VCF.
Papers published on a yearly basis
Papers
More filters
TL;DR: In this paper, a universal voltage-mode second-order filter circuit is presented. The circuit has three inputs and one low-impedance output and can realize all the standard filter functions; lowpass, high-pass, bandpass, notch, and allpass, without changing the passive elements.
Abstract: A new universal voltage-mode second-order filter circuit is presented. The circuit has three inputs and one low-impedance output and can realize all the standard filter functions; lowpass, highpass, bandpass, notch, and allpass, without changing the passive elements. The proposed circuit uses only five passive components and enjoys independent control of the natural frequency and the bandwidth, orthogonal control of the natural frequency and the quality factor, as well as low active and passive sensitivities.
21 citations
TL;DR: In this paper, the error signal rather than the input is filtered through an adjoint filter of the error channel to drive an adaptive filter which in turn drives, for example, a loudspeaker to provide destructive interference for noise cancellation.
Abstract: A multi-actuator system for active sound and vibration cancellation utilizes an LMS type algorithm having an adaptive filter. However, the error signal rather than the input is filtered through an adjoint filter of the error channel to drive an adaptive filter which in turn drives, for example, a loudspeaker to provide destructive interference for noise cancellation. The adjoint filter is realized by converting a standard filter's flow direction, such as a finite impulse response filter, swapping branching points with summing junctions and unit delays with unit advances. For multiple-input-output systems, computational complexity is significantly reduced.
21 citations
TL;DR: A methodology for microwave active filter design has been presented, and a practical implementation of a network discussed in that work is given, and the measured response is found to agree quite closely with the design specifications.
Abstract: A methodology for microwave active filter design has been presented by this author (see ibid., vol.37, no.9, p.1418-24, 1989). The present work serves to verify aspects of this design approach. A practical implementation of a network discussed in that work is given. First, an ideal preliminary design for a second-order bandpass filter is obtained. Next, the nonideal effects of the active devices and the lossy reactive elements are introduced, and then optimization is used to obtain the final design. Finally, the filter is constructed and tested. The measured response is found to agree quite closely with the design specifications. The filter section is constructed in hybrid form with lumped components, and uses two NEC 900100 GaAs FETs. The prototype accurately realizes a second-degree bandpass response with a center frequency of 6 GHz and a pole q of 2.5. >
21 citations
TL;DR: A new adaptive filter algorithm is developed that uses a penalty function formulation to place multiple constraints on the filter directly in the frequency domain, and performs better than existing ones in terms of improved convergence rate and frequency-selective limiting.
Abstract: This article develops a new adaptive filter algorithm intended for use in active noise control systems where it is required to place gain or power constraints on the filter output to prevent overdriving the transducer, or to maintain a specified system power budget. When the frequency-domain version of the least-mean-square algorithm is used for the adaptive filter, this limiting can be done directly in the frequency domain, allowing the adaptive filter response to be reduced in frequency regions of constraint violation, with minimal effect at other frequencies. We present the development of a new adaptive filter algorithm that uses a penalty function formulation to place multiple constraints on the filter directly in the frequency domain. The new algorithm performs better than existing ones in terms of improved convergence rate and frequency-selective limiting.
21 citations
TL;DR: New current-mode universal operational transconductance amplifier-capacitor (OTA-C) biquad filters based on the TG active RC filter are considered here, based on a recently proposed OTA-C based first-order all-pass network.
Abstract: The Tarmy-Ghausi (TG) active resistor-capacitor (RC) filters using op-amps and its modification by Moschytz are well known to active RC filter designers. These use first-order all-pass networks in a negative feedback loop. New current-mode universal operational transconductance amplifier-capacitor (OTA-C) biquad filters based on the TG active RC filter are considered here. These are based on a recently proposed OTA-C based first-order all-pass network. Three different feedback arrangements are investigated in the proposed filter structure so as to reduce the pole-Q sensitivity. The proposed biquad filters are shown to implement all different types of filters like low-pass, high-pass, band-pass, symmetric notch, all-pass, low-pass notch and high-pass notch. The synthesis of the general biquad is carried out in a novel way by invoking the analogy with direct-form digital filter structures. The special case of all-pass filter realisation derived from the proposed universal filter needs additional hardware for realising the feed-forward coefficients. Hence alternative OTA-C based all-pass filter implementations based on Mitra-Hirano and Gray-Markel second-order digital filter structures are derived in which the coefficients that are used to realise the denominator are shared in the realisation of numerator also. All the proposed circuits are compared with the other structures available in the literature. The simulation results of the proposed circuits are also presented.
21 citations