One factor common to many electronic devices, ranging from calculators to television sets, is the extremely high speed with which internal operations of the device are executed. Calculators, for example, appear to perform mathematical computations instantaneously. However, this is only possible because long, meticulous sequences of logical operations can be completed within time intervals that are indiscernible to the human user. Likewise, the video refreshing sequence used in CRT-based TVs for each video frame is completed rapidly enough (two interleaved sets of lines at 30 Hz) to create the illusion of persistence of the image when perceived by human eyesight.

High speed is also important for Xceive’s XC3028 single-chip silicon TV tuner, particularly for its QuickTune capability. According to Alvin Wong, vice president of marketing for Xceive, this allows the device to acquire a channel lock on the order of 10 to 15 times faster than a conventional can tuner (Xceive’s device settling time is 5 ms vs. 150 ms for conventional “can” tuners), giving television OEMs access to higher performance and enabling new features for TV sets. One feature in particular, dubbed ChannelVista, would not be possible without the high-speed channel lock of the XC3028.

The ChannelVista feature takes advantage of legacy broadcast image aspect ratios, which are 4-to-3, leaving unused area in wide screens, which typically have an aspect ratio of 16-to-9. ChannelVista utilizes this unused area to provide picture-in-picture capability without blocking the main video image. Multiple viewing fields can be monitored within two vertical regions on either side of the main image, though the refresh rate for each image decreases as the total number of images displayed increases.

Fabricated in a 0.18 μm BiCMOS SiGe process, the XC3028 provides highly integrated functionality driven by firmware. For example, there are no external LNA requirements for the input path, and a SAW filter for the output path is built into the device. Firmware programmability also enables the part to serve as a global tuner for OEMs, supporting a range of functionality equivalent to as many as 60 analog can tuner modules.

Similar aspects of the device enable the QuickTune feature. The key components are an extremely fast PLL, a built-in analog demodulator, and an on-chip DSP.

Both the XC3028 and the XC2028 have an 80 dBc dynamic range, compared to 50 dBc for a typical can tuner, according to Wong. Furthermore, these tuners can provide tighter tolerances across operating temperature and from product-to-product.

The single chip solution enables small form factors. For example, the XC3028 can enable USB dongles that receive broadcast or cable television signals. Fujitsu laptop computers have the new tuners built in, according to Wong.

The capabilities of the XC3028 suggest the evolutionary course of silicon tuners in the future. Presently, the only precision component needed by the device is a single external crystal. While future developments in MEMS technology may lead to on-chip frequency reference structures, the next likely advance would be the sharing of a single external crystal among several devices, including the silicon tuner, within a Digital TV.

Wong also stated that another development would be the obvious migration to smaller process geometries. In the case of the XC3028, this would be a migration to 0.13 μm process technology. This will occur as scalability issues of the current design are addressed.

Another option being explored is multi-chip packaging. This would have benefits for TV OEMs when implementing features such as ChannelVista, which presently requires two silicon tuners, one for the main video image, and one to support the ChannelVista feature. However, a value-added increase in the average selling price would be the main driver for this option.

One trend that may eventually encompass all of radio electronics is software-defined radio (SDR). Ideally, SDR replaces the tuning function with the high-speed analog-to-digital conversion of the raw antenna signal. The converted data is then fed to a high-performance DSP.

Wong stated that SDR for Digital TV may emerge within the next ten years. However, there are many technical issues, requiring that SDR devices be designed from the ground up, just as Xceive’s silicon tuners were designed. In order to replace silicon technology in the future, SDR must meet strict tuner performance requirements and standards. It must also be cost effective. Furthermore, there will be a transition period, as would be required for any other new technology.

Wong stated that the transition period of companies adopting the new technology is the primary challenge of gaining acceptance for silicon tuners in the marketplace at this stage of their development. He has used the analogy of transitioning from vacuum tubes to transistors to relate the benefits of migrating from can tuners to silicon tuners.

According to Wong, Xceive is planning to release a new silicon tuner that exceeds the performance of any other commercial can or silicon tuner. If the previous analogy of the transistor can be extended to include the transistor radio, it will be interesting to see what new product categories OEMs will develop using this new device.