Comtech EF Data MM200 - Manual (Page 20)

Theory of Operation MM200 High-Speed Microwave Modem
3-2 TM086 - Rev. 4.1
Figure 3-1. MM200 Microwave Modem Block Diagram
3.1.2 Data Muxiplexer
The multiplexer works on a constant output data rate. This data rate is directly related to the
symbol rate used by the modulators. The Symbol Rate is directly related to Bandwidth of the IF
carrier. The output of the multiplexer contains Reed Solomon overhead and mux/demux
overhead. The ratio between multiplexer input data and output data is 184/204. To
accommodate changes in the data rate supplied by the customer and the constant output of the
mux, the gaps are filled with null data that is later removed by the demux. Therefore, the
customer data is completely variable up to the point where the mux overflows. Variable interfaces
like the DVB ASI can take full advantage of this feature.
The single stream output of the mux is sent to a digital splitter that can have between one and
four outputs, which corresponds to the number of RF modulators installed.