Maxon Electronics Australia Pty. Ltd. MM-5500SU 사용자 설명서

FCC Documentation
MM-5500SU CDMA 1X/EVDO Modem

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9. Description of modulation system used

The CDMA Engine consists of MSM, baseband analog interface (RFT3100, S1M8656A) 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 11. CDMA digital base-band 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

base-band 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 base-band components from the CDMA low-pass filters are mixed in quadrature

with un-modulated 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.