Hybrid silicon tuners help TVs kick the CAN

October 1, 2008 OpenSystems Media

3Silicon tuners burst onto the scene four years ago with lackluster fanfare, delivering lower-quality performance than their bulky CAN tuner counterparts. However, today's production-proven silicon tuners exceed CAN tuner performance and picture quality while delivering additional benefits and differentiators. Neil explains how designers can help TV manufacturers manage the digital migration and maintain TV's relevancy by implementing second-generation silicon tuner platforms.

As TV transitions into a new digital era, an explosion of cable, satellite, terrestrial, and Internet content delivery technologies has hit the market. While these delivery mechanisms present additional options for consumers, the end viewing experience is still largely controlled by tuner performance. TV manufacturers must address critical specifications such as A74, NorDig, CableLabs, Boxer, digital sensitivity, adjacent channel rejection, and phase noise to meet terrestrial and cable requirements.

TV manufacturers must switch to different tuner architectures to meet evolving consumer and technical demands. Despite popular belief, the question is not digital versus analog. That transition is set. Analog tuners are making way for hybrid analog/digital tuners and later digital-only tuners in the 2011-2012 timeframe.

Until then, analog TV reception is still mandatory even in the United States for multiple reasons. First, U.S. multiple system operators are required to continue analog TV broadcasts for the basic network channels, including ABC, CBS, NBC, and PBS. The FCC mandated this to avoid disenfranchising cable subscribers who do not own digital TVs or digital set-top boxes. Furthermore, in anticipation of viewers connecting their new TVs to their older analog equipment such as VCRs and DVD players, TV companies are assuming that viewers will hang on to these analog products throughout their estimated 8-10 year lifetime.

Given this state of affairs, the question is not analog versus digital. The real question is CAN versus silicon.

Performance and the cliff effect

Digital reception introduces issues surrounding tuner performance and signal reception quality. With analog, TV signals deteriorate slowly over distances, but that is not the case with digital. Digital signals are either received or not whether the TV is on or off. If the TV is too far from the broadcast transmitter, viewers will only see a blank screen. Likewise, buildings, hills, and other geographical features can obstruct digital TV signals. This dramatic and sudden picture loss is referred to as the cliff effect.

CAN tuners' limited reception performance exaggerates the cliff effect. With 3 dBm better sensitivity compared to leading CAN tuners, certain silicon tuners can counter the cliff effect and be situated farther from digital transmitters without picture degradation. In fact, some silicon tuner-enabled TVs can be positioned twice as far away as equivalent CAN tuners and still receive quality signals.

The cliff effect poses an imminent challenge to the television industry as cable and satellite access is not guaranteed. For the digital transition to succeed, silicon tuners are needed to seamlessly capture digital signals over larger coverage areas and provide continuous, uninterrupted transmission.

This requirement applies to legacy analog as well as digital reception. At 3 dBm, the signal quality of a silicon tuner surpasses that of a CAN tuner, as illustrated in Figure 1. The picture is cleaner and crisper and contains better color with fewer artifacts, providing higher-quality TV services.

Figure 1

The shrinking circuit board

Beyond the digital transition, evolving consumer demands are forcing TV manufacturers to evaluate silicon tuners. Consumer tastes call for bigger, flatter, and lighter TV sets. Bulky CAN tuners cannot meet the trend as TV chassis shrink in depth, even as they expand in screen size. At some point, the desire to have increasingly thinner screens will prohibit CAN tuner use. To keep up with slimming flat-panel TV screens, TV product developers must work with constantly shrinking circuit boards.

During the past few years, hybrid analog/digital tuner module designs have provided the extra performance needed for digital TV and met TV manufacturers' requirements for analog, terrestrial, and cable reception. TV manufacturers sometimes add application-specific gain or filtering between the tuner module and the connector to enhance receiver performance. These types of designs frequently include a low-noise amplifier that provides additional gain to achieve better sensitivity in digital mode. CAN tuners that do not integrate the video and sound IF needed for analog TV reception are typically added as separate components.

TV manufacturers can achieve significant space savings with silicon tuners that incorporate these components. Silicon tuners come in a compact size – as small as 7 mm x 7 mm (~.25" x .25"), flat form factor, and depth no more than a few pieces of paper thick. Conversely, the height of CAN tuners either forces manufacturers to relocate them into separate boxes, which requires more cabling and components to be added to the home entertainment center, or prevents their use altogether.

Silicon tuners' small size also benefits TV applications that need small packaging due to shrinking screen sizes. Most small-screen TVs such as kitchen or bedroom units must add digital reception to the existing analog reception. This increases the size of the CAN tuner, making it difficult to fit into shrinking form factors. TV manufacturers can avoid this problem by migrating to silicon tuners as an enabling technology.

Reducing manufacturing complexity

CAN tuners are unique in size, material, and soldering requirements compared to other components on a PCB. TV manufacturers need specialized equipment to position CAN tuners and solder them onto a board. In many cases, CAN tuners are soldered by hand, which increases complexity, decreases yield, and necessitates specialized handling equipment and manufacturing processes.

In contrast, silicon tuners require no special handling or materials. Manufacturers can leverage the same equipment used to mount other integrated chips on a circuit board, reducing complexity and cost while increasing yield.

The semiconductor process technology at the heart of silicon tuners also features much tighter tolerances than CAN tuners. This is especially true for the coils within CAN tuners that need to be adjusted manually during manufacturing. As a result, CAN tuners are particularly susceptible to product-to-product variance.

CAN tuners usually comprise up to five large components and up to 150 small components. As a CAN tuner ages, its individual components wear at different rates. For example, coils age differently than resistors, which age differently than capacitors. This creates unpredictable reception and reduces functionality over time, which could ultimately degrade or eliminate signal reception in certain environments. Consumers demand better longevity as the costs of TV sets increase and feature sets expand.

On the other hand, silicon tuners are robust semiconductor devices with an extremely tight operating behavior that can withstand the test of time. Silicon tuners acceptable to the TV industry use a single, monolithic die with no separate pieces, meaning that little change is experienced over time due to aging components. This ensures tighter performance variations for TV sets and results in longer overall product lifetime.

It should be noted that some silicon tuners do not use a monolithic die and contain several different components within the chip package. Like the CAN tuners, these will wear differently over time and possibly raise some vibration concerns. Not all silicon tuners are created equal, and many are not suitable for use in TVs.

Reducing design costs across regions

Manufacturers cannot scale effectively to worldwide broadcast requirements without minimizing the costs between platforms across different regions. The ultimate goal is a worldwide platform that caters to the many complex regional variations for analog and digital TV, as well as the different transmitted bandwidths for audio and video.

With broadcast standards varying from region to region and the digital conversion occurring at different times, TV tuners applicable to worldwide standards help TV manufacturers reduce inventory and manufacturing costs or at least minimize any possible redesign necessary for different markets. Because silicon tuners can be used in Europe, the United States, and Asia, the tuner no longer presents an obstacle to meeting regional TV requirements.

The challenge that continually confounds CAN tuners is how to address the multifarious variations of worldwide TV standards. Many European countries transmit channels that consume 8 MHz of bandwidth per channel, while North America uses only 6 MHz. Other countries that use Phase Alternating Line (PAL) B require 7 MHz channels. Additionally, countries broadcast audio within varying bandwidth, ranging from 4.5 MHz all the way to 6.5 MHz. The modulation also varies with one standard requiring AM modulation. In addition, the international community uses different analog TV standards, as shown in Table 1.

Table 1

This complicated chart only covers analog TV standards – and only from a very high level. Digital TV is overlaid on the same channel bandwidth within each country but requires different standards throughout the world, including Advanced Television Systems Committee (ATSC) in North America; Digital Video Broadcasting (DVB) in Europe, Taiwan, and Australia; Integrated Services Digital Broadcasting (ISDB) in Japan and Brazil; and Digital Multimedia Broadcast-Terrestrial/Handheld (DMB-T/H) in China. These various standards demand a level of flexibility that a fixed-function CAN tuner either cannot support or requires additional circuitry to support each standard. Therefore, CAN tuners must be regionally specific in order to be cost-effective.

Silicon tuners can deliver one chip for all regions worldwide, regardless if the transmission is analog or digital. This simplifies product design, enabling a single platform for multiple markets instead of different chips for different regions. The chip for Europe will work in Asia and in North and South America because of its design architecture, which includes a DSP that changes the filter characteristics between different standards, enabling optimal digital filters for each mode at no additional cost. In the end, silicon tuners handle worldwide broadcast standards, simplifying inventory management and costs.

Until now, adding broadcast TV reception capabilities to an IP-based audio/video delivery system required regional standards to be introduced, negating the worldwide reach of IP. Silicon platforms enable a single worldwide TV architecture to be merged into a system receiving IP services, creating new applications not possible with CAN tuners.

DSP functionality enables flexibility

Manufacturers can reap other benefits from a DSP-based architecture. In this architecture, a DSP runs firmware that defines tuner performance, characteristics, and behavior. This allows tuners to be adjusted for specific needs, including customer differentiation, evolving customer expectations, new broadcast requirements, new broadcast standards, or nonstandard signals that are often the bane of fixed-function tuners.

Independent facilities, TV companies, and standards authorities throughout Europe, Asia, and the United States have thoroughly field-tested this silicon tuner design. During early testing, any corner case conditions were resolved by modifying the firmware running on the DSP, allowing the device to be brought to market quickly and efficiently.

The DSP also enables critical levels of performance not possible with traditional silicon tuners. TV applications demand extreme performance and strict reliability across some of the most stringent standards of any consumer application. All TV companies maintain their own requirements that can be far more onerous than those set forward by standards authorities. While CAN tuners have fixed filters that approximate the ideal with analog hardware components that deteriorate over time, DSP-based silicon tuners provide filtering that replaces these components with a tight digital implementation.

Finally, DSP performance can be used to change filtering dynamically. The DSP constantly monitors the RF front end, and filter characteristics applied to the incoming RF signal can be changed depending on the condition of that signal, as shown in Figure 2. For example, a filter can be changed as the analog RF signal deteriorates. More low-pass filtering can be applied as a counter-measure to provide a better quality display than possible with a CAN tuner under these conditions.

Figure 2

As the digital living room offers more and more sources of music, video, and other advanced data services, consumers are expecting these feature sets to be seamlessly integrated into their TVs. Today, IP delivery of these services is separate from TV services. Even the latest Apple TV and Roku boxes expect a TV to be the display device but do not integrate the TV function or vice versa. This will change as silicon tuner technology is integrated into these systems.

User experience applications

Eliminating manufacturing complexity is not enough to push manufacturers to "kick the CAN." In the end, consumer demand drives the market. Brands will differentiate their TV product lines through silicon tuners' advanced feature sets. Consumers are taking notice, forcing top brands to consider speeding the adoption cycle for silicon tuners or risk losing market share in a tight global market.

Silicon tuners can improve the overall TV experience by delivering high-quality pictures and unique features to address common consumer demands, as demonstrated by two applications in which Xceive's DSP-based silicon tuners are deployed.

ChannelVista provides multiple Picture-in-Picture (PiP) capabilities with virtual tuners that can display more than one channel on the same screen with only one tuner. By time-slicing the tuner across multiple channels, the TV System-on-Chip (SoC) can update the screen with more than one channel at the same time. This gives the illusion of PIP without the cost of additional tuners.

Another implementation is a visual channel list that displays simultaneous video from all the viewer's favorite channels on the same screen. The viewer can then select a favorite channel based on real-time video and not generic descriptions. This fine-tunes the viewing experience and allows the viewer to avoid changing to a channel during an advertisement.

In dual-tuner environments, ChannelVista enhances the viewer experience further by providing one real-time main Picture-out-of-Picture (PoP) and any number of sub broadcast PIP channels simultaneously shown around or alongside it, creating a rich media center application.

QuickTune likewise leverages silicon tuners' ultra-fast per-signal detection to provide a complete channel scan of more than 100 channels in less than 3-5 seconds. Whereas a traditional CAN tuner's channel detection time is 150 milliseconds, a silicon tuner is 30x faster at 5 milliseconds. With this technology, viewers can switch from one picture to another quickly and complete channel scan setup in a short amount of time.

Making the paradigm shift

To maintain TV's relevancy in the modern digital living room and support the smooth transition from analog to digital, engineers face a paradigm shift to meet new digital requirements. The traditional "switch" moniker is a misnomer, as reality calls for a gentle transition from analog to hybrid to digital. This requires higher-end digital TV reception while still appealing to a cost-sensitive mass market. At the same time, consumers are demanding sharper images with more color and advanced broadcast features.

These challenges are prompting design engineers to accommodate next-generation silicon tuner technology. Unlike traditional bulky CAN tuners, silicon tuners can address the problems surrounding signal reception quality and tuner performance. In addition to delivering better user experience applications, silicon tuners enable thinner TV board architectures to meet consumer demand for thinner and flatter TV screens.

In today's multimedia-hungry world, hybrid silicon tuners deliver the top performance, quality, and features required for TV markets worldwide.

Neil Mitchell is VP of marketing for Xceive, based in Santa Clara, California. He has more than 20 years of business and marketing management experience in the digital TV and semiconductor industries.


Neil Mitchell (Xceive)
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