Z87200 Datasheet, PDF (53/54 Pages) Zilog, Inc. – Spread-Spectrum Transceiver

Zilog
Z87200
Spread-Spectrum Transceiver
Reducing the carrier frequency to 25% of the clock fre- tion in the modulator, resulting in performance degrada-
quency can reduce the distortion level, as shown in Figure tion. As a rule-of-thumb, one may restrict the I.F. frequency
4 ^{21. Although the distortion is still fairly severe, adequate to 25% of the clock frequency, but, in general, each appli-}
performance may be obtainable as a result of the system’s cation and combination of PN chip rate, I.F. frequency, and
processing gain, but the performance would be many dB TXIFCLK/RXIFCLK frequency is unique and should be
off the theoretical limit. As the PN chip rate of the system evaluated before deciding whether to use the Z87200’s in-
increases, then so, too, does the effect of aliasing distor- ternal BPSK/QPSK modulator.
Figure 19. Spectrum of DDS Modulated at 0.4 x f_RXIFCLK
When Carrier Frequency is set to 0.25 x f_RXIFCLK
DS96WRL0400
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