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专利名称：Sigma-delta modulator发明人：Norsworthy, Steven Robert申请号：EP95119091.7申请日：19920520公开号：EP0709969A3公开日：19960508
专利附图：
摘要：A dither signal (18) is applied to a sigma-delta modulator (9) to remove lowlevel tones and periodic noise in the desired passband of the modulator when no, or avery low, signal is present (idle). The dither signal is a high-level signal added to the inputof a quantizer (16) in the modulator, the normalized power in the AC component thereof
being at least about of the square of the quantizer step, where N is the order of themodulator. No significant reduction in the dynamic range of the modulator results. Thetechnique may also be applied to multiple order sigma-delta modulators as well as tomultiple stage sigma-delta modulators. Further, the dither may be added at any point inthe modulator with suitable filtering of the dither. The transfer function of the filter (11₁··· 11) is proportional to the noise shaping transfer function of the modulator betweenthe point of addition of the dither and the input to the quantizer.
申请人：AT&T Corp.
地址：32 Avenue of the Americas New York, NY 10013-2412 US
国籍：US
代理机构：Buckley, Christopher Simon Thirsk
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