Abstract

Abstract Examined in this article are the critical requirements for high speed digital modem applications in a Hybrid Fiber Coax (HFC) environment. An overview of the basic elements and modulation formats of the system including the RF (Radio Frequency) tuner, IF (Intermediate Frequency) amplifiers, and frequency allocations for 2‐way transmission on a single cable are presented. A brief introduction to the data protocols and layer architectures of the modern TCP/IP internet stack is given. Requirements for IMD (Inter‐Modulation Distortion) and NF (Noise Figure) in a digital QAM (Quadrature Amplitude Modulation) system are contrasted with the traditional analog NTSC (National Television Standards Committee) format, which the cable systems were initially designed to support. RF, IF and overall system requirements for downstream and upstream data paths are presented including detailed performance requirements for AFEs (Analog Front Ends), ADCs (Analog to Digital Converters) and DACs (Digital to Analog Converters).

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