Many years ago (1978), in a former life at Zenith Electronics Corp., I co-authored a paper entitled, "A Tutorial on Ghost Canceling in Television Receivers." The paper was published in the IEEE Transactions on Consumer Electronics, February 1979. It ran 36 pages, the longest ever published by that society, and subsequently won an Outstanding Paper Award. That was long ago and all but forgotten. Surprisingly, I was asked to deliver an invited paper on a "Historical Overview of Equalization in Consumer Electronics" at the IEEE's International Conference on Consumer Electronics (ICCE) in Las Vegas last month . The ICCE immediately follows CES and has four parallel papers sessions describing the technology which will be the basis of some of the new products three to five years hence. CES, in contrast, covers what will be on sale this year.

Walter S. Ciciora, Ph.D., Recognized Industry Expert on Cable & Consumer Electronics Issues

This request gave me an opportunity to think about how technologies go through cycles in which they are very important, followed by periods when they are no longer of interest, and then important again. As an example, a good friend, Ted Hartson, likes to say, "I'm so old I remember when television came over the air and telephone calls came on a wire." Of course, now the cycle is that most television comes on a cable and more than half of phone calls come by cellular technology.

Yet another example is the implementation of color television. The first color television system standardized by the Federal Communications Commission used a monochrome picture tube and a rotating color filter wheel. That was soon canceled by the FCC and replaced with the NTSC shadow mask system. But don't think color wheels are gone. They reappeared in the color camera used during the first lunar landings. And today, they are a part of the Digital Light Processor (DLP) system of micro-mirrors commonly used in projectors for PowerPoint presentations and in some front and rear projection television displays. There is only one chip in the device and a rotating wheel provides the red, blue and green colors in rapid succession. The eye fuses the result into a color picture.

Equalization technology also has been cyclical. My interest at Zenith was in ghost canceling in television receivers. The broadcast TV signal bounces off of buildings, mountains, and even airplanes. These additional paths are longer than the main path, resulting in relative delays. This causes the received signal to be displaced to the right along the picture screen. Cable headends countered this problem either by a direct feed, or a highly directional antenna, or with the use of multiple antennas configured to cancel out the bothersome reflections.

The motivation in the Zenith case was to provide an edge over competitors' receivers. Television receiver technology had advanced to the point where the pictures were as good as the NTSC standard could deliver. All that was left was the ghost problem, which the equalizer was designed to correct. Unfortunately, the electronics were costly, slow, power-hungry, and of limited capability. And just as we had our hopes up, cable television made great strides in the marketplace. There were very few ghosts in cable signals. The economics no longer worked. Anyone who could afford a television receiver with ghost canceling was probably a cable subscriber and didn't need it. Those who didn't subscribe to cable either couldn't afford this expensive feature or had better things to do with their time than watch television. Interest in ghost canceling died.

Later, interest grew in vertical interval digital signals called Teletext. Here, equalization could be used to reduce errors in transmission. At this point, the technology matured a bit and was more capable and a bit more affordable. Just when it looked like equalization would have a role to play, it became clear that no one knew how to make money with Teletext, and it faded away in the U.S.

Next came the ATSC broadcast digital television system which required an automatic equalizer to work. The first implementation was a disaster. It required three expensive, power-hungry chips and didn't work very well. The trade press speculated that maybe broadcast digital television might not be possible. By the fifth generation, cost, power consumption and performance were under control. Recently, a sixth generation became available. We still have the economic problem. Those who could afford a digital TV will most likely be cable, DBS, or telco subscribers and not need the equalizer. Those who aren't subscribers likely can't afford the new digital receivers. But now the equalizers are "baked into" the chips. They are there, whether they will ever be used or not.

Finally, we have an application that likely will succeed and desperately needs an automatic equalizer, the portable digital television receiver. These are expected in laptops, personal digital assistants and cell phones. So the cycle is complete. A number of papers on these devices were presented at the ICCE conference. Early models were shown at CES. Now it's up to us to figure out how this fits into the cable business.

Have a comment? Contact Walt by e-mail at: wciciora@ieee.org