Television sets have changed dramatically over the past 50 years to meet evolving consumer needs. Picture quality enhancements at lower retail price points in thinner, greener television platforms continue to drive television manufacturers to seek components that reduce system cost, improve video and audio quality, and enable designs with wider screens and ultra-thin profiles. Despite these changes, the fundamental front-end tuner reception technology that determines how we receive and transmit television broadcasts has not changed in five decades.
THE EVOLUTION OF TELEVISION RECEPTION
Until recently, television broadcasts were recorded, encoded, and transmitted in analog formats such as NTSC, PAL, and SECAM. The introduction of digital broadcasts has brought a number of advantages including efficient use of bandwidth and system robustness while improving picture and sound quality. To date, many television markets have adopted digital transmissions. But at the same time, analog television continues to proliferate in major broadcast regions around the world.
In the United States, where the analog off-air shutoff is essentially complete, televisions continue to simultaneously support analog and digital cable. Since manufacturers build unified television platforms for the Americas, analog off-air support will be required for many years as Canada and Mexico’s analog off-air shutoff dates are in 2011 and 2021 respectively.
In Europe, only a select few countries have made the digital transition, but many still rely heavily on analog television. The digital transition is just starting in emerging markets in China, India, South America, the Middle East, and Southeast Asia, and many countries have no mandated date or plan to shut off their analog broadcasts.
Consequently, nearly all televisions must receive analog format signals, but a growing minority also supports digital formats such as ATSC, DVB, ISDB, and CTTB. Regardless, all signals, whether analog or digital in nature, rely on the RF domain for transmission. As such, the fundamental tuning technology has remained relatively unchanged for the past 50 years.
THE TELEVISION DEMYSTIFIED AND CHANGING CONSUMER NEEDS
A typical television receiver resides in a metal enclosure called the RF tuner module, more commonly referred to as the CAN tuner. The CAN tunes, filters, and demodulates both analog and digital broadcasts, producing signals that are processed into video and audio. The underlying functionality inside the CAN remains the same since the days of black and white television.
RF tuner modules account for most of the more than 500 million TV tuners shipped in televisions, set-top boxes, and recorder platforms in 2009, with silicon tuners accounting for a small but growing percentage. The top 10 tuner module manufacturers supply approximately 80% of the TV tuners shipped globally to the world’s largest and most respected TV manufacturers.
The integrity of the signal at each stage in the video path is crucial to the overall quality and performance of the system. A compromise of quality upstream in the signal path trickles downstream and results in visual artifacts, which tend to magnify on mid-size to large screens and degrade picture quality. For example, conventional CAN tuner designs are susceptible to interference from adjacent channels or ghosting. To attain an acceptable level of picture quality, conventional tuners require external components that add cost and space. Until recently, standard solutions involved multi-component designs requiring a number of discrete ICs from different vendors.
In addition to picture quality, TV manufacturers must address multiple global markets that support different transmission standards. In the past, different CAN tuners were required to support each regional broadcast standard, forcing television manufacturers to build different models for each region. Therefore, module makers can pass on significant cost savings to their TV customers by streamlining the supply chain, reducing the number of discrete components, and delivering a single global tuner. For example, Fresco Microchip has shipped more than 1 million global single-chip solutions that eliminate the system cost, space, and performance tradeoffs traditionally associated with CAN tuners.
THE FUTURE OF TELEVISION TUNERS
Industry experts predict that CAN tuners will account for the vast majority of tuners shipped in the foreseeable future because these modules deliver the best analog performance and lowest system cost for TV manufacturers. Silicon tuners find employment primarily in mobile, PC, or digital-only applications.
To achieve the performance required for the hybrid, analog-plus-digital, television market, the CAN tuner design (Fig. 1) is the de facto standard. It encapsulates a mixer oscillator phase-locked loop (MOPLL) IC, filters, and analog demodulator/IF processor in a single form factor, simplifying television design, integration, and manufacturability.
However, three silicon tuner architectures contend with CAN tuners in hybrid TV designs: a silicon tuner with a proprietary interface (Fig. 2) to an analog demodulator/IF processor , a silicon tuner with an open interface (Fig. 3) to popular hybrid receivers like Fresco’s FM1100 family, and a silicon tuner with integrated analog demodulator (Fig. 4) requiring an external tracking filter.
The challenge of silicon tuner configurations is balancing a cost-performance tradeoff for hybrid applications to achieve the same level of quality that RF tuner modules deliver. In spite of this, television manufacturers are using silicon tuners in a very small percentage of TV models and are willing to pay a premium to meet consumer demand for ultra-slim form factors. The broad acceptance of silicon tuners by TV manufacturers will ultimately require them to meet or exceed analog quality requirements at the competitive system price of CAN tuners.
Transitions in the television industry are slow and the migration from CAN tuners to silicon-based designs is no exception. The crossover will take several years to meet the stringent performance and cost requirements.