Efficient digital microphone decimation filter architecture
AssigneeCreative Technology Ltd
InventorDavid Philip Rossum
Life of this patent
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Abstract
A new and more efficient filtering system (e.g., digital microphone decimation filter architecture system) is described. A key to this architecture is the use of two parallel filter paths. Each path operates at the output sample rate, and comprises a shorter FIR filter followed by a series of allpass stages (e.g., implementing IIR filters). The FIR filter is designed to remove all but the last octave of out-of-band noise. The allpass stages are designed such that when the two paths are summed together, the out-of-band noise for the final octave cancels out, leaving only the desired sign.
Claims19
A decimation filtering system for processing an input signal, comprising:
- an input interface operable to receive the input signal in a bitstream;
- a filtering module operable to process the input signal through a parallel circuit of filters comprising two paths, wherein the parallel circuit of filters comprises of a FIR filter in series with an IIR filter in each of the two paths of the parallel circuit of filters;
- and
- an output interface operable to generate an output signal based on the processed input signal, wherein the FIR filter and IIR filter in each of the two paths process the input signal and the output interface generates the output signal at an identical sample rate.
A method for processing an input signal with a decimation filtering system, comprising:
- receiving the input signal in a bitstream;
- processing the input signal through a parallel circuit of filters, wherein the parallel circuit of filters comprises of a FIR filter in series with an IIR filter in each of the two paths of the parallel circuit of filters;
- and
- generating an output signal based on the processed input signal, wherein processing the input signal through the parallel circuit of filters and generating the output signal are performed at an identical sample rate.
Dependencies are inferred from the claim text.