When color TV broadcasting was adapted, the composite video signal was backward-compatible with existing black and white television sets. Receivers designed for the new color broadcast signal chiefly relied on a single component, the now famous 3.58 MHz color burst crystal, to decode the color video information embedded within the conventional black and white TV signal. With the looming nationwide transition to digital broadcasting scheduled for 2009, all conventional analog receivers will be rendered essentially inoperative. However, makers of televisions and set-top boxes that can receive both the new digital signals and analog broadcasts may be attracted to what could be the 21st-century equivalent of the color burst crystal, the silicon TV tuner.

A newly released silicon tuner product from Microtune, the MicroTuner MT2131, maintains a similar emphasis on backward compatibility by supporting multiple broadcast formats and transmission methods. The device is a single-chip silicon TV tuner that supports analog, digital, and cable TV signals. It therefore enables OEMs to provide a smooth future transition for consumers regardless of the nature of the television coverage they presently experience.

This silicon tuner can interface to either a cable TV extension or receiving antenna with simple RC networks. Due to its high level of integration, the need for several other passive components has been eliminated as well. For example, the single-ended input eliminates an external transformer balun. Tuners based on the MT2131 tuner board can therefore be approximately 65% of the size of existing “canned” tuners that are more reliant on hundreds of discrete components.

Jim Fontaine, president and CEO of MicroTune, stated that definitions for the new part started with specifications for cable television, but evolved when customers requested a component that would also meet stringent ATSC DTV receiver requirements.

Fontaine also stated that the tuner is a critical component for TV image quality, though much emphasis is placed on the television display at present. While consumers can inspect the visual quality of a display at an electronics store, this does not necessarily reveal the image quality that will be experienced in the home. However, as the number of digital television sets receiving terrestrial broadcasts grows, the importance of receiver quality will become apparent.

The MT2131 uses a patented filtering technique that improves image rejection while at the same time overall receiver sensitivity. Receiver sensitivity can have an impact on the type of antenna used to receive terrestrial broadcasts. In some communities, an antenna placed in the attic would be mandatory. While these antennas generally do not provide the sensitivity of antennas that project above the roof, that issue can be addressed through the use of a receiver with sufficient sensitivity.

The new tuner also addresses the issue of backward compatibility, which is important because different industries and geographic regions will migrate to digital broadcasting at different rates. For example, though the transition to digital terrestrial broadcasting is slated for 2009 in the United States, it could be significantly longer before a similar transition occurs in Canada, Mexico and other countries, according to Fontaine. Microtune’s customers have also expressed interest in applying the MT2131 in European and Asian markets where a transition from various analog formats to DVB-T has been underway. There is also an entire generation of legacy short-range broadcasting equipment that will still be in service beyond the expected transition to digital broadcasting, such as certain types of video surveillance cameras.

Nevertheless, the transition to digital video broadcasting is inevitable. With the availability of low-cost, high performance silicon tuners, it will also be welcomed.

Silicon TV tuners poised to replace cans
While the evolution of TV receivers has accelerated on many fronts in the last decade, fully integrated silicon tuner design has lagged behind this evolutionary wave. The silicon TV tuner is now perfected and will rapidly replace traditional can tuners, just as transistors replaced vacuum tubes during the mid-1960s...

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