The CMS0024 Multi-channel Cable Modulator encodes up to four separate transport streams for J83 or DVB-C. The resulting QAM symbols are filtered and up-converted, each channel to its own frequency division multiplex (FDM) sub channel. The IF channels are then combined output to the radio interface as a single I/Q sample stream for translation to the final RF frequency.
Although most designs will implement only one of the cable standards, it is possible to synthesise the core to support any combination of standards in a single device.
Multiple instances of CMS0024 may be used on an FPGA, sharing access to a single external RAM device. This would typically take the form of a fast SRAM (or possibly SDRAM through a suitable SDRAM controller).
Multi-core implementations typically employ separate DACs for each core with the resulting modulated baseband or IF carriers up-converted to the assigned RF frequency bands and combined to produce the wideband cable transmission signal.
