Filter
AssigneeJapanese Science and Technology Agency
InventorsKazuo Toraichi, Shuji Kawasaki
Life of this patent
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Abstract
Provided is an FIR filter capable of obtaining predetermined characteristics with a small number of input taps, delay circuits, and multipliers and achieving an improved response and low cost. In a low-pass filter, a band-pass filter, and a high-pass filter based on an FIR filter, a basic filter is configured that gives a basic impulse response function and has a filter coefficient determined from the impulse response function. Filters having different frequency characteristics are configured by changing the time scale or frequency scale of the basic filter. These filters having different frequency characteristics are combined in a cascade form or a step form, thereby constructing an FIR filter having a small number of taps.
Claims14
A filter for providing desired characteristics,
- the filter comprising a combination of a plurality of scaled filters, where said scaled filters are formed by scaling at least one basic filter in the time domain or the frequency domain, wherein said at least one basic filter comprises at least one of a basic low-pass filter and a basic high-pass filter, wherein said at least one basic filter has an impulse response function expressed by a finite piecewise polynomial and wherein said at least one basic filter has a filter coefficient which is derived from a sample point of said impulse response function;
- wherein said combination of the plurality of scaled filters is selected such that a passband width of said combination is larger than or equal to a predetermined range;
- and
- wherein the combination of the plurality of scaled filters is configured to form a passband filter and a stopband filter, wherein said formed pastband filter has passband characteristics satisfying predetermined required characteristics and wherein said formed stopband filter has stopband characteristics satisfy predetermined required characteristics.
An FIR filter for providing desired characteristics, the filter comprising a combination of a plurality of scaled filters, wherein said scaled fillers are formed by scaling basic filters in the time domain or the frequency domain based on provided input design characteristics for filter configuration;
- wherein said provided input design characteristics comprise a center frequency, a cutoff frequency, a stopband frequency, a maximum attenuation degree in a stopband, and a sampling frequency, wherein one of said basic filters comprises a basic low-pass filter and wherein another of said basic filters comprises a basic high-pass filter;
- wherein each basic filter has an impulse response function expressed by a finite piecewise polynomial and wherein each basic filter has a filter coefficient which is derived from a sample point of said impulse response function;
- and
- wherein said scaled filters are formed by scaling on the basis of a scaling factor of the highest degree;
- wherein said scaling factor of the highest degree is determined from a passband frequency width;
- said passband frequency being determined by the cutoff frequency and the center frequency;
- wherein scaled filters formed by scaling on the basis of a scaling factor of a degree lower than the the highest degree are sequentially selected;
- wherein said scaled filters are selected to keep an attenuation degree at the stopband frequency of the FIR filter lower than or equal to the maximum attenuation degree;
- the FIR filter is configured by a sequential cascade connection of the selected scaled filters;
- and
- wherein a filter gain at a frequency determined by the ratio of the sampling frequency and (scaling factor +1) is obtained as the maximum stopband attenuation degree.
A method of configuring a filter for providing desired characteristics, the method comprising
- providing at least one basic filter in the time domain or the frequency domain, wherein said at least one basic filter comprises at least one of a basic low-pass filter and a basic high-pass filter, wherein said at least one basic filter has an impulse response function expressed by a finite piecewise polynomial and wherein said at least one basic filter has a filter coefficient which is derived from a sample point of said impulse response function;
- scaling said at least one basic filter in the time domain or the frequency domain to form a plurality of scaled filters;
- [and]
- selecting a combination of said scaled filters such that a passband width of said combination is larger than or equal to a predetermined range;
- and
- further comprising configuring a combination of the scaled filters to form a passband filter and a stopband filter, wherein said formed pastband filter has passband characteristics satisfying predetermined required characteristics and wherein said formed stopband filter has stopband characteristics satisfy predetermined required characteristics.
Dependencies are inferred from the claim text.