Over the past few years, silicon tuners have been gaining momentum in the marketplace. Silicon tuners now dominate the satellite TV market as well as the handheld market. They are very popular in set-top boxes, and are gaining traction in consumer TV sets. This market acceptance has been accelerated by the benefits that silicon tuners provide over the traditional CAN tuners (named because the components are housed in a metal enclosure). These benefits include size, SW programmability, flexibility, ease of manufacture, thermal characteristics, enhanced performance and cost.
The first commercial application of silicon tuners was in the satellite market. All satellite TV reception passes through a set-top box. The size constraints of the set-top box favored the use of silicon tuners due to their small form factor.
Figure 1 : Silicon tuner size compared with a dime. Silicon tuners are much smaller than the discrete CAN tuners they replace.
The satellite standard and broadcast environment was much more suited to the early use of silicon tuners. The frequency range of the satellite systems spans only one octave (950 to 2150 MHz), and the system is not plagued with having to deal with analog interferers (as in the case of terrestrial and cable systems). The modulation schemes for satellite systems (QPSK and 8-PSK) are also less technically stringent than many terrestrial TV and cable TV systems.
The combination of these factors enabled satellite TV set-top box suppliers to take advantage of the silicon tuner's small size, lower power consumption and lower cost advantages.
Terrestrial and cable reception
Other environments, terrestrial and cable, are more challenging than those for satellite reception. For example, the frequency range from 42 to 864 MHz covers 4 octaves, and high dynamic range is necessary for terrestrial reception. The broad frequency range poses issues with filtering, local oscillator (LO) frequency generation, and the front-end low noise amplifiers (LNA). Further, the reception of analog channels has also posed challenges for silicon tuners in the past.
In order to address these environments, the front-end LNAs need to respond across a broad frequency range. This broad range means that the noise figure, distortion, and gain must meet the specifications at 42MHz, 864MHz, and all the frequencies in between. This is no small task on an integrated circuit. In other RF systems, which are narrowband, an LNA can be optimized to meet the specifications over the small frequency range of interest. This optimized LNA rarely works well in other frequency bands. The silicon TV tuner does not have this luxury.
Next: RF filtering and dynamic range
