David Carey, President, Portelligent (www.teardown.com)
TechOnline

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In growing numbers, consumers are now buying their broadcast audio despite the clutter of freely available AM and FM channels on their radio dials.

The two providers of satellite pay radio, Sirius and XM, hope that all of us spend-happy consumers keep it up and are responding to market growth with increasingly portable receiver designs to help listeners tune in anywhere in the mainland U.S.

The Delphi Roady2 XM Satellite Radio Receiver analyzed here in brief was released in mid-2004. As you might expect, analog technology mans the front lines of pulling in broadcast audio from the satellites (or potentially terrestrial repeaters) to bring an array of music, talk, news, and other programming to listeners.

Replacing the previous Delphi XM receiver's complex metal-shield-enclosed radio module is a commercially available monolithic Satellite Digital Audio Radio Service (SDARS) #MAX2140 receiver chip from Maxim. With on-chip VCO, the Bi-CMOSbased Maxim device requires only a separate IF SAW filter and reference oscillator, in this case from by RFMonolithics and KSS respectively.

Output from the receiver goes to a STMicroelectronics STA850 Source and Channel decoder chip, a big step forward in integration versus the original two-chip implementation of same. Two microprocessors and several memory components work with the decoder, including a special-purpose encryption controller, to handle user authentication. Anyone can receive the SDARS signals but only subscribers get to unlock the data stream and face the music. Demodulated and decoded music is passed to a 2-channel DAC from AKM Semi (#AK4384) and a National audio power amp (#LM4880) to complete the audio output food chain. If not using headphones, audio is coupled via a cassette adapter or a Rohm Wireless FM audio link (#BH1417F) that delivers FM-modulated audio through to an unused radio channel (ironic when you think about it).

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With further integration-driven price drops, expect more users to embrace pay-to-listen technology. Despite the "Digital Audio" moniker in SDARS, analog components play the key role of pulling in and pumping out your favorite audio—from rock to talk and everything in between.

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David Carey is President of Portelligent. The Austin, Texas company produces teardown reports and related industry research on Wireless, Mobile, and Personal Electronics. (www.teardown.com)