Tuning in DTV


This is the second article in a two-part series about over-the-air DTV reception technology, which is being added to TV sets in accordance with the FCC's tuner mandate, and plug-and-play order.

The FCC's digital tuner plan that kicked in July 1 might be more accurately described as the demodulator plan.

The demodulator is an integrated-circuit chip that takes a digital broadcast signal and turns it into the bitstream that becomes a television show in someone's home-hopefully.

The nature of 8-VSB, the modulation scheme in the digital broadcast standard developed by the Advanced Television Systems Committee (ATSC), makes demodulation difficult. It's like a beam of light in a room full of mirrors. Early demodulators were vexed by these reflected, or multipath signals.

"Traditional [analog] receivers lock onto a single signal and reject other reflected signals," said Bob Rast, president of Linx Pro Electronics, a research division of Zurich-based Micronas. With digital, "whenever the lead signal changes, the receiver breaks lock and has to re-acquire, so you get a glitch in the picture."

According to Rast and other folks who make demodulators-Zenith, ATI, Broadcom and Oren-the most recent chips defeat multipath interference. They are about to get a chance to prove the claim. Within three years, anything that picks up a TV signal will be required to handle ATSC transmissions, a la the FCC tuner mandate. (The first phase of the plan kicked in as of July 1 and applied to half of all TVs shipped-with screens 36 inches and larger.)

Additionally, TV makers are also turning out cable plug-and-play sets, and these, too, must have ATSC reception.


David Arland, vice president of corporate communications and government relations at Thomson, estimates that around 514,000 plug-and-play sets will ship during the third quarter of this year, meaning more sets with ATSC reception will hit stores in those three months than in first four years following the introduction of digital televisions into the market.

Set makers pushed for plug-and-play, though now they're casting a hairy eyeball at cable operators, who aren't keen on supplying plug-and-play cards because they prevent video-on-demand buys. (See "Can You Repeat All That?" p. 18)

The set makers were not as hospitable to the tuner mandate. Their lobby sued to bring it down and mounted a publicity campaign with the tag line, "TV tax."

Yet they knew there was an inherent risk in selling TVs that didn't receive over-the-air signals. Even the monitor-only products that make up the bulk of DTVs in homes have analog reception, according to Arland.

"Except for plasma monitors, almost all HDTV monitors have analog tuners because they start out as analog TV sets and are still used for plugging into regular cable," Arland said. "Consumers expect a TV to work like a TV, not a computer monitor."

Manufacturers say ATSC reception adds $350 to the retail price of a set. Yet much of that is for memory, which is also necessary for plug-and-play capability. Richard Lewis, senior vice president of research and technology at Zenith said adding the demodulator chip itself costs $79 in incremental manufacturing charges.

Mike Gittings, director of marketing at ATI, said his company is selling its multiformat demodulator chips for about $20. ATI's next-generation Xilleon chip, which combines multiformat demodulation with the "back-end" function of decoding, will go for $50 in quantities of 10,000, he said.


While set makers are still sore about the cost of adding ATSC reception, especially with so many broadcasters transmitting low-power DTV, they are also wary about doing it on the cheap. Thomson, for one, considers ATSC performance important because many consumers who get DISH, DirecTV or Voom satellite service will still pull local programming off the air, Arland said.


The FCC mandates were a much-needed boost for companies that made demodulator chips. With around 80 percent of American households getting television from cable or satellite, there was little motivation for TV makers to add ATSC reception to sets. And with demodulators previously trickling into digital TV sets at a rate of one for every eight built, there was little motivation-or money-to work out multipath bugs.

Consequently, the companies that make the chips are at various stages of progress. Linx, while renowned for its battle against multipath, is just now getting its technology into single-chip form. Zenith's TV-making competitors aren't flocking to buy its chips, and Broadcom is busy updating its technology, so ATI owns a big chunk of the demodulator market.

ATI's customer list includes Sony, Sharp, Philips, Panasonic, Samsung and Hisense, maker of the USDTV receivers. (USDTV is the over-the-air, multichannel service launched earlier this year in the Salt Lake City area.)

Meanwhile, Linx has hooked up with Thomson, which will integrate that company's chip into TVs starting next year.

Zenith, a division of Korea's LG Electronics, is preparing to roll out products containing the fifth generation of its demodulator technology. Generationally speaking, Zenith's first 8-VSB demodulator was a 19-by-24-inch box that came to be known as the "blue rack."

The blue rack defined the ATSC reception baseline. Subsequent generations squeezed the blue rack onto single-chip, improved-upon performance, and incorporated a digital architecture. (Generations 1-3 processed the signal in the analog domain; the switch to digital came in G4.)

Lewis said G5 improves on multipath interference, not only to the point of handling indoor reception, but mollifying 8-VSB's worst critics, as well.

"We've waited so long to see something like this," said Nat Ostroff, vice president of new technology for Sinclair Broadcast Group.

Sinclair railed against 8-VSB for years because of the multipath problems, but the company has done a 180. Ostroff said Sinclair is undertaking a campaign to promote over-the-air digital television, and to encourage its broadcast brethren to crank up to full power.

"We're preparing PSAs... promoting free, over-the-air HDTV, that will be made available to any station that wants to run them," Ostroff said.