Maxon Electronics Australia Pty. Ltd. MM-5100U User Manual

The MM-5100U 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 8-1 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.  

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