高精度Σ-△DAC中插值濾波器的研究與設(shè)計(jì):基于系統(tǒng)研究插值濾波器理論，選用了兩級(jí)半帶濾波器實(shí)現(xiàn)4×插值和級(jí)聯(lián)32×采樣保持電路，設(shè)計(jì)了一種適用于高精度音頻過(guò)采樣Σ-△DAC 的128×數(shù)字內(nèi)插濾波器。使用多相分解原理在系統(tǒng)級(jí)優(yōu)化電路結(jié)構(gòu)，并運(yùn)用CSD 編碼，使得濾波器中的乘法運(yùn)算僅需要移位實(shí)現(xiàn)，進(jìn)一步節(jié)省了硬件面積。結(jié)果表明，在系數(shù)截短至16 位字長(zhǎng)以后，總的通帶波紋不超過(guò)0.008dB，鏡像頻帶衰減大于66dB。
關(guān)鍵詞：Σ-△DAC，插值濾波器，過(guò)采樣，半帶濾波器

Abstract: Based on the systematical research on interpolation filter theory, a class of 128× interpolation filter used for audio Σ-△ DAC is presented. The digital interpolation filter consists of cascaded HBF which is followed by a 32×digital sample-and-hold circuit.Optimization is also performed so that the filter requires no multiplication and registers in the filter decreases by a half in all.
Key words: Sigma-Delta DAC, interpolator, over sampling rate (OSR), half band filter (HBF)