Interpolation filter applied to dual-channel audio delta-sigma digital-to-analog converter

Abstract

The invention discloses an interpolation filter applied to a dual-channel audio delta-sigma digital-to-analog convertor. The interpolation filter mainly comprises a two-stage half-band filter, a first-stage CIC filter and two rearranging modules, wherein a first-stage half-band filter is only realized by a multiplier, an accumulator, an RAM and an ROM, and has a very small floor area; a second-stage half-band filter uses a structure of a delay unit for an even branch multiplexing odd branch, so that the quantity of the delay units is reduced by one third; the second-stage half-band filter and the CIC filter use dual-sound channel multiplexing structures; except the delay unit, other circuits can be multiplexed by two sound channels; and the rearranging module rearranges output data of the two sound channels after each sampling rate change so as to ensure that the multiplexing of the two sound channels can be completed by using least hardware resource. The structure provided by the invention greatly saves the area of an audio DAC chip so as to reduce manufacturing cost.

Description

technical field [0001] The invention relates to a digital filter, in particular to a digital interpolation filter which occupies a small chip area and is applied to a two-channel audio delta-sigma digital-to-analog converter (DAC). Background technique [0002] Δ-ΣDAC consists of three parts, interpolation filter, digital modulator and switched capacitor filter. The interpolation filter interpolates the digital signal input at the Nyquist sampling rate, transforms it into an oversampled digital signal and sends it to the delta-sigma modulator for processing, thereby obtaining the delta-sigma bit stream. When the interpolation filter upsamples the input signal, the image frequency of the signal increases, which reduces the design difficulty of the analog anti-image filter (switched capacitor filter). This technology uses digital processing technology to reduce the requirements for analog circuits, so the area and power consumption of digital circuits, especially the interpol...

AI Technical Summary

Problems solved by technology

This technology uses digital processing technology to reduce the requirements for analog circuits, so the area and power consumption of digital circuits, especially the interpolation filter for oversampling, are relatively large.

Especially in two-channel applications, since the audio Δ-ΣDAC is a two-channel application, and the two channels require complete synchronization, if two interpolation filters are used to process the two channels at the same time, the synchronization requirement can be achieved, but Two interpolation filters make the audio delta-sigma DAC chip area larger

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