The BCM3345 combines an advanced QAM receiver; an
advanced QAM transmitter; a complete DOCSIS/EuroDOCSIS
Media Access Controller (MAC); a 140-MHz MIPS32
communication processor; a 16-bit, 100-MHz SDRAM
interface; 10/100 Ethernet MAC with integrated transceiver and
MII interface; and a USB 1.1 controller with integrated
transceiver.
The QAM receiver directly samples a tuner output with a 10-bit
A/D converter and input ACG amplifier. The receiver digitally
resamples and demodulates the signal with recovered clock and
carrier timing, filters and equalizes the data, and passes soft
decisions to an ITU-T J.83 Annex A/B/C compatible decoder. A
40-tap adaptive decision feedback equalizer is implemented.
The receiver supports variable symbol rate 64/256 QAM FEC
decoding. The final received data stream is delivered in a serial
MPEG-2 transport format. All gain, clock, and carrier,
acquisition and tracking loops are integrated in the QAM
receiver.
The upstream transmitter takes burst or continuous data, provides
FEC encoding and pre-equalization for DOCSIS/EuroDOCSIS
applications, filters and applies QPSK or QAM16 modulation to
the data stream, amplifies the signal through the integrated
upstream power amplifier, and provides a direct 0–65 MHz
analog output.