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Antialiasing And Sync-Compensation Filter

2015-01-10 03:50  
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Two dual-biquad filter chips and some external components form a multipurpose filter to reconstru
Antialiasing And Sync-Compensation Filter

ct D/A converter signals. Connected to a converter`s output, the filter provides antialiasing, reduces the D/A converter`s quantization noise, and compensates for sin(7rx)()a€”the `sync` function (attenuation). The circuit incorporates an inverse-sync function that operates to one-third of the converter`s sample rate. Beyond one-third, the filter`s response shifts to a stopband filter, which provides -70 dB attenuation. This attenuation conforms to the converter`s inherent signal-to-noise ratio and quantization error. To prevent aliasing, the stopband edge must be no higher than the Nyquist frequency (/a€? 2). To achieve 70-dB stopband rejection with this eighth-order filter requires a transition ratio (/stopband -K/passband) of 1.5, which sets the passband`s upper limit at fs 3. Notice also that you can apply a simple divide-by-64 circuit to the 192-kHz clock frequency to set the necessary 3 ratio between the converter`s sample rate and the filter`s 1-kHz corner frequency.

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