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.

Programmable universal active filter

Abstract: The invention relates to a microprocessor-programmable, universal active filter. The filter has an input section, an operational amplifier with two input nodes, a bandpass section, a lowpass section and control circuitry which, under clock control, periodically brings one of the inputs of the operational amplifier to within a low, d.c. offset voltage, approaching zero volts, of the other input. The output of the lowpass filter section is coupled to the input of the bandpass filter section and the lowpass section also has a feedback loop back to the bandpass section. The selectivity "Q", the gain, center frequency and the output characteristics, such as bandpass, lowpass, allpass, highpass or notch, of the filter may be selected using MOS switches under microprocessor control.

Improved filter for switched mode power supply

Abstract: There is provided a filter for receiving a rectangular or stepped source voltage to be filtered and for providing an output voltage, the filter including means arranged to determine the output voltage in dependence on the frequency components of the source voltage within the filter passband, and independent of output current drawn.

System and method for bandpass shaping in an oversampling converter

Abstract: A digital filter in an oversampling converter is tuned to compensate for the non-ideal frequency response of a transducer coupled to the converter. In the A/D path, the filter coefficients of the decimation filter in a sigma-delta converter are tuned to compensate for the transducer. In the D/A path, the filter coefficients of the interpolation filter of a sigma-delta converter are tuned to compensate for the transducer. Filter coefficients may be statically defined in circuitry or programmable from values stored in a storage memory. Compensation may also be accomplished by tuning capacitor ratios in a switched capacitor filter, which is typically integral to the D/A path of an oversampling converter.

A Micromechanical Parallel-Class Disk-Array Filter

Abstract: A method for realizing a high-order on-chip filter response that combines two fourth-order (i.e., two-pole) micro-mechanically-coupled MEMS-based disk-array sub-filters in a parallel configuration has been used to demonstrate a 163-MHz eighth-order (i.e., four-pole) bandpass filter with a 0.16%-bandwidth insertion loss of 2.73 dB, a 20 dB shape factor of only 1.78, and a termination impedance of only 4 kOmega, which is considerably smaller (i.e., better) than that achievable by a parallel combination of single disk resonators. The key to achieving such performance is the use of two capacitively-transduced disk-array composite sub-filters instead of the usual two stand-alone resonators used in previous parallel filter renditions. Here, the use of 275 mum times 360 mum sub-filters, each comprised of coupled radial-contour mode disk arrays, allows a combining of in-phase outputs to substantially raise output currents towards a 50times reduction in motional impedance versus that of a single disk resonator under the same operating conditions. This then lowers the termination impedance required by the overall filter, facilitating the ease with which other components can match to it, and thereby alleviating one of the primary drawbacks of capacitively-transduced micromechanical filters. By utilizing more than 128 disks and mechanical links, the 560 mum x 360 mum filter of this work comprises a true medium-scale integrated (MSI) mechanical circuit on a chip.

Low component current-mode universal filter

Abstract: A low component current-conveyor based current-mode universal filter with one input and three outputs is presented. The filter can simultaneously realise lowpass, highpass and bandpass responses. Realisation of notch and allpass responses does not require additional active elements. The proposed circuit enjoys low active and passive sensitivities.