BCM3125 - QAMLink® Universal Set-Top Box Transceiver

QAMLink® Universal Set-Top Box Transceiver

The Broadcom BCM3125 combines an in-band 256-QAM receiver, an out-of-band QPSK receiver and a 4/16-QAM transmitter, providing an integrated set-top box or cable modem front-end solution.

The in-band receiver in the BCM3125 directly samples a 36-44 MHz carrier frequency with a l0-bit A/D converter, which is preceded by a programmable gain amplifier (PGA). The in-band demodulator consists of a quadrature mixer and multi-rate filters that convert the oversampled IF data stream to a baseband complex data stream. The I and Q baseband signals are then filtered by dual square-root Nyquist filters that can accommodate roll-off factors of 12-18% for various ITU-T J.83 Annex A/B/C applications. A 32-tap decision feedback equalizer (DFE) with 8 feedforward taps and 24 feedback taps is implemented to remove the ISI generated by worst-case coaxial cable and wireless cable channels. The equalizer coefficients are updated every baud cycle for fast convergence. Two distinct forward error correction (FEC) methods are supported. The first standard, ITU-T J.83 Annex A/C, is also referred to as the DVB, DVB interactive or DAVIC standard. The second, ITU-T J.83 Annex B, is variously known as DigiCipher II® , DOCSIS and SCTE DVS-031.

  • Universal set-top and cable modem front-end supporting the ITU-T J.83 Annex A/B/C standards as well as OpenCable, EuroDOCSIS, and DVB/DAVIC
  • Represents a complete solution for dual downstream channels (In-Band and Out-of-Band) and the upstream channel
  • Includes direct interface to the OpenCable Point of Deployment (POD) module