scispace - formally typeset
Search or ask a question
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
More filters
Patent
11 Nov 1999
TL;DR: In this article, a surface acoustic wave (SAW) filter is used for cellular phones and other mobile communication equipment. The SAW filter of the present invention comprises comb-shaped electrodes facing each other disposed on the same piezoelectric substrate, at least two resonators with an input and output terminals, and an equivalent transmission line which is connected between an output terminal of a first resonator and an input terminal of another resonator.
Abstract: The present invention relates to a surface acoustic wave (SAW) filter which is used for cellular phones and other mobile communication equipment. The object of the present invention is to realize a SAW filter of which attenuation characteristics and pass characteristics can be set arbitrarily. The SAW filter of the present invention comprises comb-shaped electrodes facing each other disposed on the same piezoelectric substrate, at least two resonators with an input and output terminals, and an equivalent transmission line which is connected between an output terminal of a first resonator and an input terminal of a second resonator. The phase of the transmission line can be adjusted from 5 degrees to 175 degrees arbitrarily at the series resonance frequency of the resonators. This structure realizes a band-stop filter or a band-pass filter whose attenuation characteristics and pass characteristics can be set arbitrarily.

28 citations

Patent
09 Sep 1991
TL;DR: In this paper, a linear phase high pass filter with an electronic delay is presented to remove baseline wander from an ECG signal, where the low pass filter passes the low frequency baseline signal while blocking the ECG signals comprised of higher frequency components than the cutoff frequency.
Abstract: A linear phase high pass filter having a linear phase low pass filter in parallel with an electronic delay means is disclosed to remove baseline wander from an ECG signal. The linear phase low pass filter is preferably a digital Infinite Impulse Response (IIR) filter. An input ECG signal is simultaneously presented to an IIR low pass filter and an electronic delay. The low pass filter passes the low frequency baseline signal while blocking the ECG signal comprised of higher frequency components than the cutoff frequency of the low pass filter. Thereafter, the outputs from the IIR low pass filter and delay are passed to a summer that subtracts the output of the low pass filter from the output of the delay to produce the output of the filter. The combination of the output of a low pass filter being subtracted from a delayed input signal produces a high pass filter. The resulting high pass filter has a -0.3 dB cutoff frequency of about 0.5 Hertz while providing a virtually constant group delay for the ECG signal passed through the filter.

28 citations

Patent
25 Mar 1993
TL;DR: In this article, a new passive harmonic filter was proposed to improve the overall system performance by drastically reducing the line side current harmonics generated by all variable frequency drive power centers. But, the harmonic filter caused an overvoltage across the VFD terminals because of its increased capacitive reactance at the fundamental frequency, which was overcome by using the buck transformer.
Abstract: A Variable Frequency Drive Power Center incorporating a new passive Harmonic Filter in an improved housing structure for Variable Frequency Drives (VFDs). The new harmonic filter improves the overall system performance by drastically reducing the line side current harmonics generated by all VFDs. The harmonic filter includes a series inductance, a parallel capacitance, and a buck transformer. The filter provides a low impedance path for the harmonic currents generated by VFD and therefore prevents them from flowing into the input ac power lines. The filter also improves the input power factor of the VFD system because of its increased inductive reactance under full-load conditions. Although the filter causes an overvoltage across the VFD terminals because of its increased capacitive reactance at the fundamental frequency this problem is overcome by using the buck transformer. The power center includes a separate section for the harmonic filter and a set of vertically-disposed compartments for mounting a plurality of VFDs on sliding assemblies. This provides a more efficient use of space and ease of maintenance, service and inspection of each individual unit.

28 citations

Patent
12 Sep 2001
TL;DR: In this article, a signal generator of known source resistance applies a.c. signals successively over a range of frequencies to filter inputs, and a voltmeter monitors the voltage across the filter inputs.
Abstract: Electrical filter circuits are tested by connecting to the filter inputs without the need to connect to the filter outputs or to disconnect the outputs from a load. A signal generator of known source resistance applies a.c. signals successively over a range of frequencies to the filter inputs, and a voltmeter monitors the voltage across the filter inputs. Different types of filter have different characteristic shapes for the voltage/frequency curve, and processing is applied to the measured results in a compute to determine the location of inflections in the curve and other characteristics of the curve. Methods are disclosed for determining the values of the individual sub-components of the filter. Where the filter is an L-C filter, an interactive process is applied to successively improve the accuracy of the component value determinations. Using the techniques described enables the insertion loss of the filter also to be readily calculated by the computer.

28 citations

Patent
04 Feb 1999
TL;DR: In this paper, a bandpass filter consisting of a Gm-C filter having a transconductance is adjusted to achieve a center frequency within a predetermined range with respect to the desired center frequency.
Abstract: A signal having a substantially uniform spectral distribution, e.g., a flat noise signal such as a signal ground, is provided at the input of a bandpass filter such as an IF filter of a receiver circuit, to thereby produce an output signal at the output of the bandpass filter. The output signal is processed in a limiter to produce a limited signal. An average frequency of the limited signal is determined, and the bandpass filter is adjusted based on the determined average frequency. According to one embodiment of the present invention, the bandpass filter comprises a Gm-C filter having a transconductance, and the filter is adjusted by adjusting the transconductance of the Gm-C filter based on the determined average frequency. According to another aspect of the present invention, a desired center frequency for the bandpass filter is identified. A resolution and a desired confidence interval are also identified. The number of samples of the limited signal needed to achieve the identified desired resolution and confidence interval is determined based on the identified desired center frequency. An average frequency is determined by sampling the limited signal to obtain a plurality of samples, the number of the plurality of samples being at least as great as the determined number of samples of the limited signal to achieve the identified desired resolution and confidence level, and determining the average frequency from the plurality of samples. The bandpass filter is adjusted based on the determined average frequency to achieve a center frequency for the bandpass filter that is within a predetermined range with respect to the desired center frequency. Related apparatus are also discussed.

28 citations


Network Information
Related Topics (5)
Capacitor
166.6K papers, 1.4M citations
86% related
Amplifier
163.9K papers, 1.3M citations
85% related
Voltage
296.3K papers, 1.7M citations
84% related
CMOS
81.3K papers, 1.1M citations
83% related
Integrated circuit
82.7K papers, 1M citations
82% related
Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20239
202229
20201
20188
2017150
2016199