Z87200 데이터 시트보기 (PDF) - Zilog

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Z87200

SPREAD-SPECTRUM TRANSCEIVER

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Z87200

Spread-Spectrum Transceiver

FUNCTIONAL BLOCKS (Continued)

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Figure 7. PN Matched Filter

Power Detector

The complex output of the PN Matched Filter is fed into a

Power Detector which, for every cycle of the internal base-

band sampling clock, computes the magnitude of the vec-

tor of the I and Q channel correlation sums,

I2(K)+Q2(k), where the magnitude is approximated as

Max{Abs(I),Abs(Q)} + 1/2 Min{Abs(I), Abs(Q)}.

This 10-bit value represents the power level of the corre-

lated signal during each chip period and is used in the

Symbol Tracking Processor.

Symbol Tracking Processor

The output of the Power Detector Block represents the sig-

nal power during each chip period. Ideally, this output will

have a high peak value once per symbol (that is, once per

PN code cycle) when the code sequence of the received

signal in the PN Matched Filter is the same as (and is

aligned in time with) the reference PN code used in the PN

Matched Filter. At that instant, the I and Q channel outputs

of the PN Matched Filter are, theoretically, the optimally

despread I and Q symbols.

4-18

DS96WRL0400

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