AR# 15412

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LogiCORE DA FIR Filter v.7 - What is zero-packing? Why can I only use zero-packing in interpolation or interpolated modes?

Description

Keywords: zero, pack, DA FIR, filter, interpolation, interpolated

What is zero-packing? Why can I only use zero-packing in interpolation or interpolated modes?

Solution

"Zero-packing" means that zeroes are inserted between the coefficients. A zero-packing of 3 indicates that 3 zeros are inserted between every coefficient; this creates an interpolated filter, which is typically used to create cheaper narrow band filters. However, this is still a single-rate FIR filter.

An interpolation filter zero-packs the data stream, and the zero-packing factor is inferred through the sampling rate change (a rate change of 4 means a zero-stuffing of 3). However, the zero-packing is never actually implemented, and a polyphase structure is used. (This is much more efficient, as multiplying by zero is a waste of logic.)

If you require a sample rate change, use the interpolation filter.
AR# 15412
Date 04/01/2009
Status Archive
Type General Article
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