Digital satellite radio, one of the fastest growing consumer electronics products in years, is near the top of the list of most requested options for new cars and trucks. Available through subscription, XM Radio and Sirius Satellite Radio both broadcast 100 channels of high-quality digital audio from satellites that provide continuous coast-to-coast coverage with music, sports, news, and talk.
Silicon Laboratories' all-CMOS two-chip set should make it easier to fabricate these satellite radios and serve the burgeoning market. Designed to the XM Radio standard, the Si2210 RF/IF tuner and the Si2200 RF/IF synthesizer reduce pc-board space by 60% and cut component count by 70%, significantly lowering the radio's bill of materials.
This dual-path, superheterodyne CMOS chip set enables reception from the satellite or a terrestrial repeater in urban areas that have dense buildings and other structures blocking satellite signals (see the figure). The two receive paths permit satellite and repeater diversity reception simultaneously. Or, the radio may combine the satellite and terrestrial signals into one path.
The 2.3-GHz satellite signals are downconverted to an IF of 119.6 MHz, where they're filtered with a surface-acoustic-wave (SAW) filter and downconverted to baseband. A 23.92-MHz crystal sets the clock frequency that's shared with the synthesizer.
The Si2200 synthesizer chip produces the RF and IF local oscillator frequencies. It integrates the RF and IF voltage-controlled oscillators, varactors, and loop filters, thereby eliminating most external components. The Si2201 and Si2200 both have a serial peripheral interface (SPI) used with an embedded controller to provide software control and monitoring.
The Si2210 is packaged in a 64-pin TQPF, and the Si2200 comes in a 28-pin MLP. Chip-set prices begin at $8.85 in 10,000-unit quantities. Samples are available now. An evaluation board is available for $150.