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2.1.9

Sum Chain

CDMA

DUCB

CDMA

DUCA

Or1UMTSChannel

DUC11

CDMA

DUCB

CDMA

DUCB

CDMA

DUCA

CDMA

DUCA

Or1UMTSChannel

DUC1

DUC0

SUM0

SUM1

SUM2

ToScaleand

RoundBlock

SUM3

DUCs

2-10

GC5318

HIGH-DENSITY DIGITAL UPCONVERTER

SLWS187 – JULY 2006

Figure 2-15. Sum Chain

The sum chain is a daisy-chain of all DUC outputs into four independent composite output streams. Each

DUC output drives four complex adders, each summing the DUC contribution into the sum chain.

The DUC output data driving the adders is 21 bits. The sum chain partial sum outputs are 26 bits wide to

allow for word growth. Each DUC output can contribute to any of the four sum chains via programmable

enable lines. The output of the last daisy-chained sum is then the composite of all of the 24 CDMA or 12

UMTS channels. There must be no DUCs powered down within a sum chain that have lower numbers

than those that are active. This condition would break the chain. For example, if DUCs 3-5 are used and

active, DUCs 0-2 must not be powered down.

As shown in Figure 2-15, each DUC contains a portion of the sumchain. Individual sum chain outputs can

be summed together using the parameters below.

GC5318 Operation

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