QAM and QPRS digital broadband cable systems

K. Sreenath, Kamilo Feher, Iwao Sasase

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)


The performance of high‐level modulation schemes in non‐linear broadband digital communication systems is investigated. The tolerance of 16‐, 64‐, 256‐QAM and 49‐, 225‐QPRS schemes to these non‐linearities is given in terms of their phase margins. Our research results show that high level QAM schemes are less sensitive to non‐linearities when operated in offset mode. Comparison of non‐linearly amplified broadband QAM and QPRS schemes reveals that QPRS schemes need less carrier‐to‐noise ratio (CNR) than corresponding QAM schemes for identical operating conditions. Also, when the non‐linearities are not severe, the degradation in performance is controlled by AM/PM characteristic of the broadband amplifier.

Original languageEnglish
Pages (from-to)139-148
Number of pages10
JournalInternational journal of digital & analog cabled systems
Issue number3
Publication statusPublished - 1989
Externally publishedYes


  • Digital broadband systems
  • Digital communications
  • Modulation
  • Spectral efficiency

ASJC Scopus subject areas

  • General Engineering
  • Computer Networks and Communications
  • Electrical and Electronic Engineering


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