Abstract: A meter electronics (20) having a notch filter (26) configured to filter a sensor signal from a sensor assembly (10) in a vibratory meter (5) is provided. The meter electronics (20) includes the notch filter (26) communicatively coupled to the sensor assembly (10). The meter electronics (20) is configured to receive the sensor signal from the sensor assembly (10), the sensor signal being comprised of a first component at a resonant frequency of the sensor assembly (10) and a second component at a non-resonant frequency and pass the first component and substantially attenuate the second component with the notch filter, wherein the first component is passed with substantially zero phase shift.

Abstract: Sense amplifiers for use in connection with microelectromechanical system (MEMS) gyroscopes are described. The sense amplifiers may be configured to change the level of a gyroscope signal, i.e., the signal produced by a gyroscope in response to angular motion, to a level suitable for processing circuitry arranged to infer the angular velocity. The sense amplifier may further provide a DC discharge path allowing for discharge of the DC component of the output signal. The DC discharge path may include an anti-aliasing filter and a resistive circuit. The anti-aliasing filter may filter the output signal to maintain the resistive circuit in the linear region. The anti-aliasing filter may be designed with a frequency response such that discrete frequency sub-bands are blocked or at least attenuated. The frequency sub-bands may be tuned to substantially match the gyroscope's resonant frequency and its integer multiples.

Abstract: A method including applying a first excitation voltage to an electrode of a touch sensor which charges a capacitive node associated with the electrode from a first voltage level to a second voltage level that is greater than the first voltage level. A first measurement measures a charge to change from the first voltage level to the second voltage level. A second excitation voltage is applied to the electrode which charges the capacitive node from the second voltage level to a third voltage level that is greater than the second voltage level. The capacitive node is discharged from the third voltage level to a fourth voltage level that is less than the second voltage level. A second measurement measures a charge to change from the third voltage level to the fourth voltage level. A measured charge signal is generated based on the first measurement and the second measurement.

Abstract: A circuit for controlling a capacitor having a capacitance adjustable by biasing, including an amplifier for delivering a D.C. bias voltage, having a feedback slowed down by a resistive and capacitive cell.

Abstract: Reflectionless low-pass, high-pass, band-pass, band-stop, all-pass, and all-stop filters, as well as a method for designing such filters is disclosed, along with a method of enhancing the performance of such filters through the use of sub-networks to further modify and improve the frequency response. These filters preferably function by absorbing the stop-band portion of the spectrum rather than reflecting it back to the source, which has significant advantages in many different applications. The sub-networks preferably offer additional degrees of freedom by which the leakage through the parent filter may be cancelled or reinforced to alter cutoff sharpness, stop-rejection, or other measures of performance.

Abstract: An improved biquad infinite impulse response filter is shown that may be implemented in a very large instruction word digital signal processor as well as in other processing circuitry. The new filter structure modifies the feedback path in the filter, resulting in a significant reduction in execution cycles.

Abstract: Reflectionless low-pass, high-pass, band-pass, band-stop, all-pass, and all-stop filters, as well as a method for designing such filters is disclosed, along with a method of enhancing the performance of such filters through the use of sub-networks to further modify and improve the frequency response. These filters preferably function by absorbing the stop-band portion of the spectrum rather than reflecting it back to the source, which has significant advantages in many different applications. The sub-networks preferably offer additional degrees of freedom by which the leakage through the parent filter may be cancelled or reinforced to alter cutoff sharpness, stop-rejection, or other measures of performance.

Abstract: One apparatus includes a notch filter that has a state observer unit and a parameter adaptation unit. The state observer unit is configured to receive a sampled noisy electrical signal and a sampled filtered electrical signal, the state observer unit having an estimated noise signal output, the estimated noise signal output carrying an estimated noise signal to be subtracted from the sampled noisy electrical signal, resulting in the filtered electrical signal. The parameter adaptation unit is configured to receive the estimated noise signal and an error signal from the state observer unit. The parameter adaptation unit is also configured to determine, based on the estimated noise signal and the error signal, an updated estimated noise frequency, thereby causing the state observer unit to generate an updated estimated noise signal to be provided on the estimated noise signal output.

Abstract: Embodiments of the present invention reduce or eliminate the need for fixed frequency high Q band filtering for both full duplex (FDD) and half duplex (TDD) systems. Transceiver architectures according to embodiments of the present invention can be designed to have a single input/output for both FDD and TDD based standards. Further, according to embodiments, because the duplexer and/or SAW power losses are lowered or removed altogether, the system power output requirements can be met more easily and with higher efficiency.

Abstract: An analog filter is presented that comprises a chain of filter stages, a feedback resistor for providing a negative feedback, and a feedback capacitor for providing a positive feedback. Each filter stage has an input node and an output node. The output node of a filter stage is connected to the input node of an immediately succeeding filter stage through a resistor. The feedback resistor has a first end connected to the output node of the last filter stage along the chain of filter stages, and a second end connected to the input node of a first preceding filter stage. The feedback capacitor has a first end connected to the output node of one of the chain of filter stages, and a second end connected to the input node of a second preceding filter stage.

Abstract: A radio transmitter front end for use in a radio frequency (RF) transceiver includes at least one amplifier stage operable to generate a transmit signal in response to an upconverted signal. A feedback generator is operable to generate a transmit feedback signal in response to the transmit signal. A control signal generator is operable to generate at least one filter control signal in response to the transmit feedback signal. A notch filter is operable to filter out of band noise while passing in-band frequencies to the at least one amplifier stage, under control of the at least one filter control signal.

Abstract: Embodiments of the invention disclose a signal processing device and a signal processing method and a device and a method for signal processing. The signal processing device includes a sampling module, a first segmentation module, a second segmentation module, and a detection module. The sampling module samples an input signal to generate a sample signal. The first segmentation module calculates a first segment value according to the sample signal during a first time interval. The second segmentation module calculates a second segment value according to the sample signal during a second time interval different in length from the first time interval. The detection module generates a detection signal according to the determination of whether the first segment value lies out of a first range, and whether the second segment value lies out of a second range.

Abstract: A method, computer program product, and computer system for determining a magnitude and phase of a spurious-free dynamic range component. A first signal and a second signal may be received from a first source operatively connected to a differential component. A first output associated with the first signal and a second output associated with the second signal may be nulled. The first signal and the second signal may be shorted. A second source operatively connected to the differential component may be disconnected. The first signal of the first source may be applied at a same phase as the second source with an additional phase delta, +Yo. A first differential residual signal may be measured using the first signal at the same phase as the second source with the additional phase delta, +Yo. The second signal of the first source may be applied at the same phase as the second source with an additional phase delta, ?Yo.

Abstract: A filter comprises an integrator, a signal feeding path, a first operational amplifier and a second capacitor. The integrator comprises a first input terminal and a first output terminal. The signal feeding path comprises: a first resistor, having a first terminal coupled to the first output terminal; a first capacitor, having a first terminal coupled to the second terminal of the first resistor; and a second resistor, having a first terminal coupled to the integrator and having a second terminal coupled to the second terminal of the first capacitor. The first operational amplifier comprises a second input terminal coupled to the second terminal of the first resistor and the first terminal of the first capacitor, and comprises a second output terminal. The second capacitor comprises a first terminal coupled to the second terminal of the first capacitor, and comprises a second terminal coupled to the second output terminal.

Abstract: Methods and apparatus, including computer program products, are provided for filtering. In some example embodiments, there is provided an apparatus including a first differential amplifier including a first positive input, a first negative input, and a first output, wherein the first positive input is connected to the first output via at least a first capacitor, and wherein the first negative input is connected to the first output via at least a first resistor; and a second differential amplifier including a second input, a third input, and a second output, wherein the second input is connected to the second output via at least a third resistor, wherein the third input is connected to the second output via at least a second capacitor, and wherein an input is connected to the first positive input and the second input via at least a third capacitor. Related apparatus, systems, methods, and articles are also described.

Abstract: An apparatus for active feed forward electromagnetic interference (EMI) filtering, including, a noise detection and current reconstruction circuit that receives EMI noise occurring at a noise source, and noise voltage compensation circuit operatively coupled to the noise detection arid current reconstruction circuits. The active feed forward circuit generates a noise voltage compensation signal based on the EMI noise reconstructed by the noise detection circuit.

Abstract: An acquired signal indicative of electrophysiological activity is filtered using both a wavelet filter and either a notch filter or a band-pass filter to eliminate noise or interference, such as power line interference. A wavelet transform is used to transform the acquired signal into the wavelet domain, where a wavelet filter is applied to extract a soft component (e.g., a component with small wavelet coefficients). A filter, such as a notch filter or a band-pass filter, is applied to the soft component in order to isolate an interference signal. The interference signal is used to produce an output signal representing the acquired signal filtered to eliminate the interference signal. For example, the interference signal may be subtracted from the acquired signal. Alternatively, the output signal may be reconstructed from respective hard and soft components of the acquired signal as transformed into the wavelet domain.

Abstract: An active noise cancellation device (2) for a medical device includes an active circuit having a first input connection (8), a second input connection (10), and an output connection (12). The second input connection (10) is connected to at least one predetermined reference signal. The active noise cancellation device (2) further includes a low-impedance body connection electrode (4) adapted to be in electrical contact with a bloodstream of a subject, wherein the low-impedance body connection electrode (4) is connected to said first input connection (8), and a feedback branch (14) connecting the output connection (12) with the first input connection (8). The feedback branch (14) comprises a current limiting circuit (18) to limit a current through said feedback branch (14) to be lower than a predetermined current.

Abstract: The low frequency notch filter integrated circuit is implemented in a relatively small silicon area and with high linearity, thereby promoting the utilization of very large-scale integration (VLSI) techniques in biomedical instrumentation. The filter circuit utilizes R-2R ladders providing area saving of approximately 120:1. R-2R ladders function as digitally programmable resistors in a biquad configured Operational Amplifier filter circuit. Integrator loop topologies are used in the filter circuit. The preferred topology utilizes a Tow-Thomas circuit, which can be designed for the prerequisite gain and Q independently selecting two resistors. In addition, the three op amps in the Tow-Thomas topology have their non-inverting input grounded, and therefore their inverting inputs will be held ideally at virtual ground. These feature permits the use of op amps with small common mode input range.

Abstract: A signal filter and accompanying methods. In one embodiment, the filter includes a first mechanism for receiving a first signal. A second mechanism employs one or more modified representations of the first signal to cancel one or more frequency components of the first signal, yielding an output signal in response thereto. In a more specific embodiment, the first mechanism includes a splitter for receiving the first signal and splitting the first signal onto a first path and a second path. The second mechanism further includes one or more delay modules and one or more phase shifters in the first path and/or the second path. One or more controllable amplifiers are optionally included in the first path and/or the second path. The one or more delay modules, phase shifters, or amplifiers are responsive to one or more control signals from a controller. The controller is adapted to modify behavior of the second mechanism so that the filter is characterized by a desired frequency response.

Abstract: A switched capacitor notch filter for sampling an input signal using multiple sampling capacitors during multiple non-overlapping time periods. The charge from one set of sampling capacitors is averaged and transferred to the filter output during one non-overlapping time and the charge from another set of sampling capacitors is averaged and transferred to the filter output during a second non-overlapping time period.

Abstract: A relaxation oscillator for generating a first and a second oscillation signals, comprising: a reference-voltage providing circuit for providing a high and a low reference voltages; switches for directing the high and low reference voltages to inputs of a transconductance amplifier and a non-inverting input of a comparator; the transconductance amplifier for generating an output current with a value determined by its transconductance value, controlled by an input tuning voltage, and multiplied by its inputs' voltage difference; a capacitor connecting between the transconductance amplifier output and ground; and the comparator for generating a first and a second digital signals; wherein the first and second digital signals are digital control signals to the switches, and the first and second oscillation signal of the relaxation oscillator respectively; wherein the oscillation frequency of the relaxation oscillator is independent of the reference voltages, achieving accurate frequency turning, and simplifying t

Abstract: In varying embodiments, the present inventive concepts relate to a notch filter for quadrature and differential signaling. No inductor is used in this notch filter, thus the integrated circuits silicon die area is small. In addition, the linearity of the notch filter is excellent because of the linearity of the resistors and capacitors in integrated circuits.

Abstract: There is provided a filter circuit that includes a flying capacitor and a capacitor that is provided in parallel with the flying capacitor, between an input terminal and an output terminal of the flying capacitor. As the capacitor that has a predetermined capacity is provided between the input terminal and the output terminal of the flying capacitor, it is possible to provide steep attenuation characteristics in the filter circuit provided with the flying capacitor.

Abstract: There is provided with a filter circuit, including: an input terminal configured to input signals; a band stop filter configured to have a center frequency of input signals from the input terminal in a stop band and configured to reflect signals in the stop band that is included in the input signals and pass signals outside the stop band; a band pass filter configured to have a pass band including the stop band, and configured to pass signals in the pass band out of the signals having passed through the band stop filter; a synthesis circuit configured to synthesize the signals reflected on the band stop filter and the signals having passed through the band pass filter to obtain synthesis signals; and an output terminal configured to output the synthesis signals.

Abstract: Apparatus and methods for providing integrated RF notch filter subsystems having enhanced Q values are described. An integrated notch filter includes an LC filter element and a Q-enhancement circuit coupled to the LC filter element, with the Q-enhancement circuit configured to offset resistive losses in the LC filter element to adjust the Q value of the filter system. A transceiver having multiple LNAs for various bands may be provided to a single notch filter system including a Q-enhancement circuit.

Abstract: A switched capacitor notch filter for sampling an input signal using multiple sampling capacitors and multiple non-overlapping time periods. The charge from the sampling capacitors is averaged and transferred to the filter output during another non-overlapping time period.

Abstract: A plurality of low-pass filters (2-1, 2-2, 2-3) are cascaded to the post stage of an OTA (1) and a plurality of high-pass notch filters (3-1, 3-2, 3-3) are cascaded further to the post-stage thereof so that a high-pass filter having a Q is not connected to the output of the OTA (1) having a high output impedance and a capacitor having a low capacitance is not connected with the output of th OTA (1) thus preventing multifeedback and avoiding such problems as the zero point of the notch filter (BEF) deviates from a design value or oscillation takes place.

Abstract: A signal filter and accompanying methods. In one embodiment, the filter includes a first mechanism for receiving a first signal. A second mechanism employs one or more modified representations of the first signal to cancel one or more frequency components of the first signal, yielding an output signal in response thereto. In a more specific embodiment, the first mechanism includes a splitter for receiving the first signal and splitting the first signal onto a first path and a second path. The second mechanism further includes one or more delay modules and one or more phase shifters in the first path and/or the second path. One or more controllable amplifiers are optionally included in the first path and/or the second path. The one or more delay modules, phase shifters, or amplifiers are responsive to one or more control signals from a controller. The controller is adapted to modify behavior of the second mechanism so that the filter is characterized by a desired frequency response.

Abstract: A control system for an AC line voltage distribution system includes a DC energy storage system and an inverter coupled to the DC energy storage system adapted for coupling to the AC line distribution system. A proportional-integral voltage regulator coupled to the DC energy storage system receives a voltage signal for the DC energy storage system and receives a voltage reference. In an exemplary embodiment, the voltage regulator includes a proportional path and an integral path to receive the DC voltage information and the voltage reference signal information, a filter to remove an AC component having a predetermined frequency contained in the DC voltage signal, and an output terminal to output a control signal with the AC component removed.

Abstract: An integrated front-end filter for a tuner provides an array of from several to a multitude of passbands, each for passing at least one but less than all channels designated in a band of frequencies. Each passband is exclusively selectable. The integrated front end filter includes at least one active filter unit with an active reactance element in either of fixed and variable filter configurations and a decoder coupled to said at least one active filter unit and being responsive to a control signal for selecting a one of the passbands. In one example a multitude of active filter units of fixed filter configuration provide the multitude of passbands. Each data is stored at a predetermined location and reproduced in response to a corresponding control data signal from a tuner controller. Each data characterizes one of the plurality of passbands. The filter element is switchable from one passband to another in response to the control data signal.

Abstract: An acquired signal indicative of electrophysiological activity is filtered using both a wavelet filter and either a notch filter or a band-pass filter to eliminate noise or interference, such as power line interference. A wavelet transform is used to transform the acquired signal into the wavelet domain, where a wavelet filter is applied to extract a soft component (e.g., a component with small wavelet coefficients). A filter, such as a notch filter or a band-pass filter, is applied to the soft component in order to isolate an interference signal. The interference signal is used to produce an output signal representing the acquired signal filtered to eliminate the interference signal. For example, the interference signal may be subtracted from the acquired signal. Alternatively, the output signal may be reconstructed from respective hard and soft components of the acquired signal as transformed into the wavelet domain.

Abstract: A plurality of low-pass filters (2-1, 2-2, 2-3) are cascaded to the post-stage of an OTA (1) and a plurality of high-pass notch filters (3-1, 3-2, 3-3) are cascaded further to the post-stage thereof so that a high-pass filter having a high Q is not connected to the output of the OTA (1) having a high output impedance and a capacitor having a low capacitance is not connected with the output of the OTA (1) thus preventing multifeedback and avoiding such problems as the zero point of the notch filter (BEF) deviates from a design value or oscillation takes place.

Abstract: Apparatus, systems, and methods implementing techniques for filtering signals are described. A filter circuit receives an input signal and produces a corresponding filtered signal. The filter circuit has a transfer function that relates the filtered signal to the input signal. The transfer function includes at least one pole and at least one zero, where at least one of the zeros corresponds to a first frequency, and at least one of the poles corresponds to a second frequency. The apparatus also includes a negative-transconductance circuit that is coupled to the filter circuit and that increases a magnitude of a component of the filtered signal that corresponds to the second frequency.

Abstract: A low noise nth order filter, system, and method includes a plurality of nested general immittance converters (GICs) operatively connected to one another in successive GIC stages; and a capacitor operatively connected to each of the GICs, wherein a first successive GIC stage begins at a first node located in between a previous GIC stage and a corresponding capacitor operatively connected to the previous GIC stage. A second successive GIC stage begins at a second node located in between the first node and the first successive GIC stage. The filter may further comprise a resistor operatively connected to at least one successive GIC stage, wherein the resistor is preferably located in between the first node and the first successive GIC stage.

Abstract: A filtering apparatus and method for dual-band sensing circuit are disclosed. The invention features a dual-band sensing unit disposed in a filtering device that receives the signals from a sub-system with variable frequency spectrum. The signals are split up into several bands. After that, one or more frequency detecting units are used to detect the power of high-band and low-band signals, and convert the power into a voltage signal. Users can externally adjust the gain of a tunable gain amplifier for the voltage signal. Further, a comparison operation is processed by a comparator, and a signal resulted from the comparison operation is used to control the switch timing for an RF switching unit. Consequently, this like adaptive notch filter is achieved to determine the intensity of noise and thereby to turn on the high-band or low-band notch filters, so as to reduce the in-band loss.

Abstract: A transconductance filtering device with a flexible architecture that can selectively present a different topology and/or order beginning with the same initial structure is disclosed. For example, depending on the communications standard detected, the elementary cells of the filtering circuit required to form the adapted filter are selected and connected in such a manner as to obtain the configuration desired for the filtering means. As an example, the filter may be for use with a wireless communications system forming, in particular, a cellular mobile telephone. The filter is configurable by means of at least two elementary cells of the same structure and of controllable interconnection means each having an open or closed state.

Abstract: Switched capacitor notch filter circuits are disclosed.

Abstract: Control system for programmable filters, master-slave calibration system and fully programmable high precision filter for use in such control system, such filters being provided with a filter input and a filter output including a first, first order low pass filter section comprising first and second mutually identical operational transconductance amplifiers (OTAs), having a controllable transconductance Gm from a differential voltage input having first and second differential voltage input terminals to a single current output carrying a single phase current output signals, said first and second OTAs being provided with first and second control inputs, respectively, said filter input being coupled to the first differential voltage input terminal of said first OTA.

Abstract: Switched capacitor notch filter circuits are disclosed.

Abstract: Embodiments of the invention provide an adaptive notch filter that employs a power detector as a feedback control mechanism to steer the notch filter. One such embodiment of the invention provides adaptive control of the notch filter capacitor to tune the notch filter frequency based upon a diode power detector. One embodiment of the invention provides a system including multiple cascaded adaptive notch filters each having a feedback control method from a power detector to separately control each filter. For one embodiment of the invention a method is disclosed for tuning an adaptive notch filter using a dithering process to determine a minimum power output at the power detector. One embodiment includes an adaptive notch filter implementing a device with a tunable resonance frequency.

Abstract: A bandpass filter circuit 10 of the present invention includes: transconductance amplifier circuits 1 to 3; a common-mode feedback circuit 4 which outputs a first control signal to the transconductance amplifier circuit 1 so that a D.C. voltage level of a differential output of the transconductance amplifier circuit 1 is at a predetermined level; a common-mode feedback circuit 5 which outputs a second control signal to the transconductance amplifier circuit 2 so that a D.C. voltage level of a differential output of the transconductance amplifier circuit 2 is at a predetermined level; and capacitors C1 to C3. Each of the members are connected as shown in FIG. 1. With the configuration, a bandpass filter circuit capable of adjusting constants such as a Q-value is realized.

Abstract: An absorptive bandstop filter includes at least two frequency-dependent networks, one of which constitutes a bandpass filter, that form at least two forward signal paths between an input port and an output port and whose transmission magnitude and phase characteristics are selected to provide a relative stopband bandwidth that is substantially independent of the maximum attenuation within the stopband and/or in which the maximum attenuation within the stopband is substantially independent of the unloaded quality factor of the resonators. The constituent network characteristics can also be selected to provide low reflection in the stopband as well as in the passband. The absorptive bandstop filter can be electrically tunable and can substantially maintain its attenuation characteristics over a broad frequency tuning range.

Abstract: A trap filter comprises a delay circuit made up of switched capacitors for delaying an input signal and outputting a delay signal, and an adding circuit for adding the input signal and the delay signal.

Abstract: A communication filter circuit useful in a dual-mode receiver comprises a cascade of an active twin-T filter and a passive twin-T filter sections defining sharp notches at the center of second adjacent and of third adjacent channels, respectively, and specifically providing most attenuation at 60 kHz and at 90 kHz, for operation in the ISM136 band which has 30 kHz channel spacing. Since communication is channelized and limited in bandwidth, an active/passive twin-T notch filter structure is effective for signal attenuation. In a circuit in which real and imaginary signal components are processed, active-passive twin-T filters are provided in each of four signal paths, namely I and ?I, Q and ?Q.

Abstract: A biquad notch filter includes a first stage having first and second admittances of a first type connected between an input terminal and the control terminal of a transistor, a first current source connected between a first supply terminal and a first terminal of the transistor, a second current source connected between a second terminal of the transistor and a second supply terminal; a third admittance of a second type connected between the control terminal and the second supply terminal, a fourth admittance of a second type connected between the first admittance and the second terminal; and a second stage having a transconductance, including a fifth admittance of the first type, connected between the control terminal and an output terminal, a sixth admittance of the first type connected between the output terminal and the second supply terminal, and a connection of the first terminal to the output terminal.

Abstract: Disclosed is apparatus for operating with an RC filter (26, 26A), and a corresponding method. The apparatus includes circuitry (32) for use in measuring an actual value of at least one filter component and a controller (34), coupled to the measurement circuitry, for determining at least one adaptive filter (36, 46) coefficient using the measured actual value to so as to compensate for a deviation of at least one filter component value from an ideal value. Where the filter is embodied as an RC network, the circuitry measures an actual value of both a resistor and a capacitor, and the controller uses the measured actual value of the capacitor when determining the value of a resistor.

Abstract: The object of the present invention is to obtain a high precision notch filter or all-pass filter. Therefore, two transconductance circuits for adjustment, which perform a voltage-current conversion of a difference between a voltage of a filter input terminal and a voltage of a filter output terminal, are added to two integrators comprising two transconductance circuits for the integrators, and two capacitors. An output current of one transconductance circuit for adjustment is added to an output current of the transconductance circuit for the integrators, and an output current of the other transconductance circuit for adjustment is subtracted from an output current of the transconductance circuit for the integrators. Therefore, by adjusting conductance values of the two transconductance circuits for adjustment, even when non-ideal characteristics would exist in the transconductance circuits for the integrators, those can be canceled.

Abstract: The present invention provides an active low-pass filter system including a low-pass filter circuit and at least one frequency-rejecting network coupled to the low-pass filter circuit. The frequency-rejecting network is included in a resistive forward signal flow branch of the low-pass filter. The present invention also provides a power amplifier system for driving a load. The power amplifier system includes a pulse width modulation circuit which creates ripple spectra, an error amplifier and modulator circuit, and a demodulation filter connected in series, and a feedback control loop coupled to the pulse modulation circuit and including an active low-pass filter having a feedback demodulation filter and an isolated-integrator frequency-rejecting network.

Abstract: A notch compensation apparatus and method comprising, based on input to and output from a notch filter, dynamically calculating a desired change to a notch frequency of the notch filter and specifying the desired change to the notch filter so as to cancel an input resonance of uncertain or time varying frequency.