Page 275 - DSP Integrated Circuits
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260 Chapter 6 DSP Algorithms
Figure 6.54 Functional pipeline
6.8.4 Pipeline Interleaving
Pipeline interleaving can be used, for example, when several signals are to be pro-
cessed by the same algorithm [13, 14, 18, 19]. We demonstrate pipeline interleav-
ing by means of an example. Consider a second-order section in direct form with
the transfer function
Now, if each delay element is replaced by two delay elements, we obtain a
structure with the transfer function
Hence, the transfer function is modified, but now we also interleave the input
sequence with zeros. The new input sequence becomes
The output of the pipelined filter becomes
Hence, the proper output sequence is obtained by decimating the sequence
Y^z) by a factor two. The maximum sample rate has been increased by a factor
two, but only every other output value is of interest. In reality we have not gained
anything. However, two independent sequences can be filtered by the same filter
as illustrated in Figure 6.55. This technique can be used to map algorithms onto
systolic and wave front arrays as well as for programming heavily pipelined stan-