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US 7,584,235 B2Granted
Variable passband autoregressive moving average filter
AssigneeTektronix, Inc.
InventorKevin M. Ferguson
Life of this patent
Estimating the term…
Abstract
A variable passband ARMA filter has as inputs a signal to be filtered, a reverse version of the signal to be filtered and a variable coefficient to produce as an output a filtered signal. The variable coefficient is generated by a variable equivalent sample rate coefficient converter having as inputs an initial coefficient and a variable resampling rate parameter which controls the passband.
Claims5
A filter having a variable passband comprising:
- a filter circuit having as inputs a signal to be filtered (a forward signal) and a reverse version of the signal to be filtered (a reverse signal), and having as an output a filtered signal as a function of a variable coefficient;
- and
- a variable equivalent sample rate coefficient converter having an initial coefficient as an input together with a variable resampling rate parameter that determines the variable passband, and providing as an output the variable coefficient as a function of the variable resampling rate parameter;
- wherein the filter circuit comprises:
- a first IIR filter having the forward signal and the variable coefficient as inputs, and providing as an output a first filtered signal;
- a second IIR filter having the reverse signal and the variable coefficient as inputs, and providing as an output a second filtered signal;
- and
- means for combining the first and second filtered signals with the forward signal to provide the filtered signal;
- wherein the combining means comprises a summing circuit having as inputs the first and second filtered signals and the forward signal, and providing as an output the filtered signal;
- and
- wherein each IIR filter comprises:
- a gain stage having an input coupled to receive an input signal, and providing an output in response to a gain component of the variable coefficient;
- and
- a decay stage having an input coupled to the output of the gain stage, and providing as an output a filtered input signal in response to a decay component of the variable coefficient.
11 more elements
A filter having a variable passband comprising:
- a filter circuit having as inputs a signal to be filtered (a forward signal) and a reverse version of the signal to be filtered (a reverse signal), and having as an output a filtered signal as a function of a variable coefficient;
- and
- a variable equivalent sample rate coefficient converter having an initial coefficient as an input together with a variable resampling rate parameter that determines the variable passband, and providing as an output the variable coefficient as a function of the variable resampling rate parameter;
- wherein the filter circuit comprises:
- a first IIR filter having the forward signal and the variable coefficient as inputs, and providing as an output a first filtered signal;
- a second IIR filter having the reverse signal and the variable coefficient as inputs, and providing as an output a second filtered signal;
- and
- means for combining the first and second filtered signals with the forward signal to provide the filtered signal;
- wherein the combining means comprises:
- an input multiplier having as inputs the forward signal and an all pass gain coefficient derived from the variable coefficient and the variable resampling rate parameter, and providing an output;
- a summing circuit having as inputs the first and second filtered signals and the output from the input multiplier, and providing as an output a preliminary filtered signal;
- and
- an output multiplier having as inputs the preliminary filtered signal and a gain correction coefficient to provide overall gain for the filter, and providing as an output the filtered signal.
10 more elements
A filter having a variable passband comprising:
- a filter circuit having as inputs a signal to be filtered (a forward signal) and a reverse version of the signal to be filtered (a reverse signal), and having as an output a filtered signal as a function of a variable coefficient;
- and
- a variable equivalent sample rate coefficient converter having an initial coefficient as an input together with a variable resampling rate parameter that determines the variable passband, and providing as an output the variable coefficient as a function of the variable resampling rate parameter;
- wherein the filter circuit comprises:
- a first IIR filter having the forward signal and the variable coefficient as inputs, and providing as an output a first filtered signal;
- a second IIR filter having the reverse signal and the variable coefficient as inputs, and providing as an output a second filtered signal;
- and
- means for combining the first and second filtered signals with the forward signal to provide the filtered signal;
- and
- wherein the variable coefficient input to the first and second IIR filters is a decay component of the variable coefficient.
7 more elements
Dependencies are inferred from the claim text.