BCM3137 - QAMLink® QPSK/16-QAM Burst Demodulator

QAMLink® QPSK/16-QAM Burst Demodulator

The Broadcom® BCM3137 QAMLink® UniversalQPSK/16 QAM Burst Receiver is a complete single-chip cable network receiver, that accepts QPSK and 16 QAM upstream burst data in a frequency-agile, time-division multiple access (TDMA) scheme. An analog front-end (AFE), a QAM demodulator and an FEC decoder are integrated on this single chip. The AFE performs coarse gain setting and A-to-D conversion on either an IF input or baseband I/Q inputs. A digital down-mixer translates the input spectral center to true DC. The I and Q samples pass through dual decimators and square-root raised cosine filters with an excess bandwidth α = 0.25. Fast burst detection and acquisition are performed on the preamble with programmable length and pattern. The chip incorporates unique word (UW) detection in the preamble process to delineate the packet and resolve phase ambiguity. Carrier phase offset is removed by a derotator. An adaptive equalizer characterizes the RF channel response and removes inter-symbol interference (ISI) caused by micro-reflections. The FEC decoder consists of a programmable derandomizer and a programmable RS decoder. FIFO buffers provide input/output data rate de-coupling for the FEC decoder.

The BCM3137 delivers the recovered data stream and accepts receiver control inputs through a receive interface linked to an MCNS MAC chip. The BCM3137 prepends ranging and data information to each received code word and packet for processing by the BCM3210B. An ATM UTOPIA-like receive interface is also supported in a bit-serial style. The BCM3137 can be configured through either an SPI or I2C-compatible serial interface.

  • The Broadcom® BCM3137 is a headend QPSK/QAM burst receiver for CMTS applications
  • Variable symbol rates from 100 kBaud up to 5.12 MBaud
  • Analog front-end featuring dual gain stages and dual 10-bit ADCs, plus a 6-bit ADC to estimate wideband channel