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Abstract

A method and means for filtering the quantization noise from the output of a 1-bit analog-to-digital converter (noise-shaping coder) is disclosed. The A/D utilizes oversampling of the analog input signal, and decimation of the digital output signal. The multiplierless low-pass filter is comprised of a coefficient ROM for storing the filter coefficients, a counter for addressing the memory, and a true/complement gate for selectively complementing the output of the memory in response to the 1-bit data stream from the noise-shaping coder. An accumulator sums the selectively complemented output words for all samples, and the accumulated output is then applied to the decimator. A second embodiment is also disclosed which utilizes an overlapping digital filter approach, wherein a plurality of digital multiplierless filters are overlapped to provide an arbitrary length filter capable of producing an arbitrary filter response.

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First Claim