Digital TV gets an analog lift - Embedded.com

Digital TV gets an analog lift

The Dish Network 332 receiver is one of several customer-premises equipment boxes available for satellite TV programming. Using a constellation of nine satellites, Dish delivers digital video, data and audio channels of programming to a rooftop. Despite the digital nature of satellite content, it all starts with an analog radio front end and the supporting analog power supply components.

Virtually all components in the Dish 322 box are mounted to one side of a large circuit board within a sheet-metal enclosure. Interestingly, the unit could have been substantially smaller, but cost constraints and, to some extent, consumer expectations for receiver box size allow Dish to buck the diminutive-form-factor drivers from the portable electronics world. A two-layer pc board with generously spaced surface-mount and through-hole components supports most chips and helps keep cost down.

All I/Os to the unit are via threaded coax receptacles and RCA jacks that, along with a phone jack and S-Video socket, are mounted to the back of the unit. The user interfaces and a smart-card receptacle for user authentication are on the front.

The receiver centers on a Broadcom chip set. Two separate RF analog satellite inputs each connect to a Broadcom BCM3440 receiver. These chips in turn are connected to Broadcom BCM4500 tuners, which connect to the Broadcom BCM7319 STB decoder chip. The decoder is mounted in a 456-I/O BGA package; the rest are mounted in leaded SMT packages.

The receiver chips and tuner chips sit atop dense arrays of vias on the main board for thermal management. A separate remote antenna board, with a Melexis TH71101 FSK/FM/ASK receiver, provides a mechanism for external programming to merge with satellite-based content.

A second, shielded daughtercard packs a Motorola MC44BC374 phase-locked-loop-tuned modulator to launch received programming onto a standard TV cable outlet. A Silicon Labs telephone interface chip set (Si3021 and Si3012) is also used.

The estimated cost of manufacturing hovers around $90, a figure offset by the various programming and box rental fees associated with Dish service. Hardware enables the Dish service-and, in turn, analog components enable the hardware.

David Carey, president of Portelligent (www.teardown.com), a producer of teardown reports and related industry research on wireless, mobile and personal electronics.

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In Brief
Though digital satellite subscriber growth is stagnating in mature markets, worldwide the number is expected to grow by 40 million through 2008, from 61 million active subscribers at the end of 2003 (InStat/MDR). Total revenue is expected to reach $70 billion by 2008. Vying for a slice of that market is the Dish 332 receiver. Designed around a Broadcom chip set, the receiver's guts reside in a two-layer printed-circuit board, with generously spaced SMT and through-hole components supporting most chips. A separate antenna board from Melexis and a daughtercard containing a Motorola PLL-tuned modulator form the TV outlet. Because the satellite system relies on standard telephone service to handle traffic for programming and authentication, a Silicon Labs telephone interface chip set is also used. Estimated cost of manufacturing? $90.

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