Directly tuned filter and method of directly tuning a filter
First Claim
1. A method of tuning an analog filter comprising:
- a) filtering an input signal with the analog filter to produce a filtered signal, the input signal being such that the filtered signal has a frequency response representative of that of the analog filter;
b) performing an analog-to-digital conversion on the filtered signal to produce digital filtered signal samples;
c) processing the digital filtered signal samples to determine at least one characterizing filter parameter;
d) adjusting the analog filter based on the analog at least one characterizing filter parameter; and
e) providing the input signal with substantially flat spectral densityf) repeatedly performing steps (a) through (e) until the characterizing filter parameters satisfies at least one objective.
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Abstract
A Method for filter tuning using direct digital sub-sampling is provided. The tuning is accomplished in the digital domain by determining the filter characteristics from the shape of the transfer function. The input signal (1) is passed through the filter (3) and is then sub-sampled by and Analog-to-digital Converter (ADC) (5). The sub-sampled signal (6) is then processed in the digital domain using a digital circuit (7) that is used to determine the center frequency (Fc) and Quality factor (Q) and/or other important filter parameters. The Fc, Q and/or other important filter parameters are then adjusted by generating digital control signals (8) that can be converted to analog signals (10) using Digital-to-analog Converters (DACs) (9).
46 Citations
19 Claims
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1. A method of tuning an analog filter comprising:
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a) filtering an input signal with the analog filter to produce a filtered signal, the input signal being such that the filtered signal has a frequency response representative of that of the analog filter; b) performing an analog-to-digital conversion on the filtered signal to produce digital filtered signal samples; c) processing the digital filtered signal samples to determine at least one characterizing filter parameter; d) adjusting the analog filter based on the analog at least one characterizing filter parameter; and e) providing the input signal with substantially flat spectral density f) repeatedly performing steps (a) through (e) until the characterizing filter parameters satisfies at least one objective. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. The method of tuning a multi-stage analog filter comprising:
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a) setting characterizing parameters of all filter stages of the multi-stage analog filter to default values; b) filtering an input signal with a specified filter stage of the multi-stage analog filter to produce a filtered signal, the input signal being such that the filtered signal has a frequency response representative of that of the multi-stage analog filter; c) performing analog-to-digital conversion on the filtered signal to produce filtered signal digital samples; d) processing the filtered signal digital samples to determine at least one characterizing filter parameter of the specified filter stage; e) adjusting the specified filter stage based on the at least one characterizing filter parameter; and f) repeating steps b) through e) to adjust the at least one characterizing filter parameter of a subsequent each other filter stage of the multi-stage analog filter.
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12. An apparatus comprising:
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an analog filter adapted to filter an input signal to produce a filtered signal, the input signal being such that the filtered signal has a frequency response representative of that of the analog filter; an analog-to-digital converter adapted to sample the filtered signal to produce filtered signal digital samples; a digital circuit adapted to process the filtered signal digital samples to determine at least one characterizing filter parameter and to adjust the filter based on the at least one characterizing filter parameter, wherein the input signal has a substantially flat spectral density wherein the apparatus is adapted to repeatedly adjust the filter until each characterizing filter parameter satisfies at least one objective. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19)
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Specification