QAM for terrestrial and cable transmission

Author

Bryan, David A.

Author_Institution

Philips Lab., Briarcliff Manor, NY, USA

Volume

41

Issue

3

fYear

1995

fDate

8/1/1995 12:00:00 AM

Firstpage

383

Lastpage

391

Abstract

We introduce quadrature amplitude modulation (QAM) and discuss QAM architectures used to overcome transmission impairments typically encountered on 6 MHz wide terrestrial and cable TV VHF/UHF channels. The input data to the QAM transmitter is mapped into N bit words called symbols; N determines the QAM level. The signal-to-noise ratio at the receiver determines the QAM level that can be used. Typical terrestrial and cable channels allow N=4 and N=8, leading to user data rates of about 20 and 40 Mbits/s, respectively. Transmission impairments include random noise, reflections, phase noise, and frequency offset. Adaptive equalizers are used by the cable and terrestrial QAM receivers to remove amplitude and phase distortion due to reflections and filter imperfections. The cable adaptive equalizer consists of feed-forward and feedback sections; the terrestrial equalizer uses a feed-forward section only. Both the cable and terrestrial receivers accomplish both start-up and steady-state equalization using only the user data. We also describe carrier recovery and symbol timing recovery for the terrestrial receiver

Keywords

UHF radio propagation; VHF radio propagation; adaptive equalisers; cable television; quadrature amplitude modulation; radio receivers; telecommunication channels; television broadcasting; timing; 20 Mbit/s; 40 Mbit/s; QAM architectures; QAM transmitter; VHF/UHF channels; adaptive equalizers; amplitude distortion; cable channels; cable transmission; carrier recovery; data rates; filter imperfections; frequency offset; phase distortion; phase noise; quadrature amplitude modulation; random noise; receiver; reflections; signal-to-noise ratio; symbol timing recovery; terrestrial channels; terrestrial transmission; transmission impairments; Acoustic reflection; Adaptive equalizers; Cable TV; Communication cables; Feedforward systems; Frequency; Phase noise; Quadrature amplitude modulation; Signal to noise ratio; Transmitters;

fLanguage

English

Journal_Title

Consumer Electronics, IEEE Transactions on

Publisher

ieee

ISSN

0098-3063

Type

jour

DOI

10.1109/30.468056

Filename

468056