Maxon Electronics Australia Pty. Ltd. MM-5500U ユーザーズマニュアル
FCC Documentation- MM-5500U CDMA 1x/EVDO Modem
21/22
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9. Description of modulation system used
The MM-5500U CDMA card consists of MSM, baseband analog interface (RFT31000, IFR3300) as
modulation system. The MSM integrates functions of a CDMA processing, a digital FM(DFM)
processing, CDMA subsystem in the MSM performs CDMA signal processing about CDMA
modulation / demodulation, viterbi coding/decoding, interleaving/de-interleaving, and etc.
The CDMA baseband processor performs forward-link demodulation, time tracking and reverse-link
modulation for CDMA digital signals. The following figure shows a CDMA digital baseband processor
block diagram.
Figure 9.1 CDMA digital Baseband Block Diagram
The modulator performs the orthogonal modulation, long code PN spreading and quadrature
spreading. The resulting data stream is then band limited with FIR filters and sent to the analog
baseband processor.
The RFT3100 Transmit Signal Path (shown in figure 8-2) accepts analog I and Q data from the MSM
and outputs modulated IF centered at 138.6 MHz to the RF transmitter. The RFT3100 transmit path
outputs a differential IF signal with spread spectrum modulation expending ±630KHz from the
transmit IF center frequency of 138.6 MHz.
The analog I and Q baseband components from the CDMA low-pass filters are mixed in quadrature
with unmodulated I and Q signals at 138.6 MHz. After mixing, the I and Q IF components are
summed and output differentially. The 138.6 MHz I and Q IF VCO signals are generated on the
RFT3100.