BCM3138

Description

The BCM3138 QAMLink® Universal QPSK/QAM burst receiver is a highly integrated solution that significantly decreases the board space and cost of demodulators in digital cable modem head-ends applications. The BCM3138 provides two independent cable network receivers that accept QPSK and m-QAM burst data in frequency-agile, time-division multiple access (TDMA) schemes. Advanced features in the BCM3138 include an analog front end (AFE), a QAM demodulator, a generalized equalizer and an enhanced Reed Solomon (RS) FEC decoder with dynamic deinterleaving.

The AFE provides coarse gain setting and A-to-D conversion (ADC) on either an IF input or baseband I/Q inputs. When the internal ADC is bypassed, the on-chip digital mixer translates the desired signal at RF to true DC where the I and Q samples pass through variable decimators and matched raised-cosine filters. The BCM3138 incorporates unique word detections of programmable length and pattern in the burst preamble for signal acquisition as fast as 16 symbols. An adaptive equalizer and ingress canceller characterizes the RF channel response, cancels ingress noise and removes inter-symbol interference (ISI) caused by micro-reflections in the channel.