Digital high definition television testing in North America

Abstract

The transmission of digital television signals involves the modulation of carriers: a single carrier per channel (SCPC) or multiple carriers per channel (MCPC), The 8-VSB modulation scheme adopted by the Grand Alliance in the United States is an SCPC one. An earlier alternative considered was a two-carrier scheme devised by the Advanced Television Research Consortium (ATRC), among whose members are Philips, Thomson, and the David Sarnoff Research Center, companies wellknown in Europe. The number of carriers may be in the thousands, as in the COFDM (coded orthogonal frequency division multiplexing) scheme which is currently under development in Europe and Japan. Each of these schemes could employ at least one of the well-known digital modulation systems, such as quadrature amplitude modulation (QAM), which requires that both sidebands be carried by the channel, or a vestigial sideband (VSB) system, which uses a single-sideband amplitude modulation method. Transient peak-to-average power of a digital television signal is of considerable importance as it affects the economics of terrestrial broadcasting, at least in the classic sense where one high-power transmitter serves a community. The Advanced Television Test Centre (ATTC) method of measurement can be carried out using generally available RF test equipment, and it has been shown to yield the same results as specialized test equipment.