Digital decimation filter having finite impulse response (FIR) decimation stages
First Claim
1. A digital filter circuit, comprising:
- a plurality of cascaded integrator stages coupled to an input of said digital filter circuit; and
a plurality of cascaded finite impulse response (FIR) filter stages, wherein a first one of said FIR filter stages has an input coupled to an output of a last one of said integrator stages, wherein a transfer function from said input of said digital filter circuit to an output of a last one of said FIR filter stages has a finite DC gain and a frequency domain shaping characteristic, and wherein said last FIR filter stages is decimated substantially with respect to said output of said last integrator.
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Accused Products
Abstract
A digital decimation filter having Finite Impulse Response (FIR) decimation stages provides improved performance over a Hogenauer decimating filter. The filter comprises multiple integrator stages followed by multiple FIR decimating stages. The zeros of the filter are tunable by adjusting the integer coefficients of the FIR stages providing tunability of the cut-off response, as opposed to the fixed sinc response of the Hogenauer filter. As a result, the number of required stages for a particular steepness is reduced, dramatically reducing the amount of digital circuitry required to implement a particular filter design. The improved filter is especially suitable for use in digital intermediate frequency (IF) stages in receivers, and for code-based applications where selectable decimation rate is desired and a fast multiply is not available.
9 Citations
18 Claims
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1. A digital filter circuit, comprising:
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a plurality of cascaded integrator stages coupled to an input of said digital filter circuit; and a plurality of cascaded finite impulse response (FIR) filter stages, wherein a first one of said FIR filter stages has an input coupled to an output of a last one of said integrator stages, wherein a transfer function from said input of said digital filter circuit to an output of a last one of said FIR filter stages has a finite DC gain and a frequency domain shaping characteristic, and wherein said last FIR filter stages is decimated substantially with respect to said output of said last integrator. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A digital filter circuit, comprising:
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a plurality of cascaded integrator stages coupled to an input of said digital filter circuit; and filter means having a predetermined order for providing decimation and a stopband having a rate of gain reduction greater than that of a sinc transfer function of equivalent order to said predetermined order. - View Dependent Claims (11, 12)
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13. A method for processing a signal in the digital domain, comprising:
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integrating said signal by a predetermined integration order; filtering said signal through a plurality of finite impulse response (FIR) filter stages to produce a result consistent with a finite DC gain and a frequency domain shaping characteristic, and wherein filtering further decimates substantially a result of said integrating. - View Dependent Claims (14, 15)
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16. A digital signal processing system, comprising:
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a memory for storing program instructions and data; and a processor coupled to said memory for executing said program instructions, wherein said program instructions comprise program instructions for integrating said signal by a predetermined integration order, decimating substantially a result of said integrating, and filtering said signal by programmatic implementation of a plurality of finite impulse response (FIR) filter stages to produce a resulting consistent with a finite DC gain and a frequency domain shaping characteristic. - View Dependent Claims (17, 18)
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Specification