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Motorola chipset digitally tweaks analog radio

Posted: 03 Oct 2002 ?? ?Print Version ?Bookmark and Share

Keywords:Motorola? symphony chipset? am radio chipset? analog radio chipset? symphony dsp?

As satellite digital radio services struggle for survival and terrestrial digital radio broadcasting in the United States faces at least three more months of dead air, Motorola Inc. is going retro, gambling on old-fashioned analog AM/FM.

Motorola's Semiconductor Products Sector is rolling out a "digital radio" chipset, called Symphony, designed to improve tuning, filtering and audio processing of analog AM/FM broadcast signals.

Leveraging software algorithms on a 24-bit DSP-based baseband/audio processor with 1,500MIPS of processing power, Symphony radio "can offer consumers less static, fading, pops and hisses while allowing them to receive more AM/FM radio channels," said John Hansen, strategic-marketing director for driver information systems at Motorola.

The company claims that the disparity in sound quality between analog radio and Symphony-based digitally processed radio is comparable to the difference between the sound quality of cassettes and CDs.

Symphony radio will get its first public airing this week in Los Angeles, California at the Audio Engineering Society's 113th annual convention, which opens October 5.

Citing the existence of 4,400 AM/FM radio stations worldwide, Hansen said, "Motorola made a conscious decision to go where the money is, with our options open for the future."

As competitors like Texas Instruments, Philips Semiconductors, STMicroelectronics and Agere Systems plunged into IC development for the various digital radio broadcast standards, Motorola said it spent five years developing software-based technologies to enhance analog radio reception.

The company has filed 18 patents covering RF, high-speed analog processing and digital logic processing to improve analog radio tuning in software running on a DSP, Hansen said.

Motorola and others have previously used DSPs to enhance audio - simulating concert-hall sound, for example - once the signal is digitized in a home theater or audio system or a high-end car radio. But Hansen called Symphony digital radio unique because the company "designed our DSP system architecture so that software tuning and audio processing can be handled through a single software thread."

Of the 1,500MIPS available on the 24-bit Symphony DSP, Motorola's engineers allocated 150MIPS for general audio processing and divided the remaining 1,350MIPS into nine independent cores, minimizing delays by allowing them to run different software in parallel, explained Hansen.

The Symphony hardware is a three-piece chipset. An RF front-end chip capable of AM, FM, and weather-band tuning receives the analog radio signal. An IF analog interface chip digitizes that signal. Then the 24-bit baseband audio DSP takes over to perform tuning and audio processing in software.

Radio system designers can exploit a variety of software algorithms already developed for the Symphony DSP, which has been used in such products as mastering and commercial-theater surround-sound systems; home-entertainment systems; and MP3, CD, and DVD digital audio players.

The current baseband processor is based on an 0.18?m process, but the production model for Symphony digital radio will be manufactured on a 0.13?m process, Hansen said. "Motorola has worked up a complete package of chips, software and marketing that will make Symphony easy for 'unsophisticated' radio manufacturers to use," said independent semiconductor analyst Jim Turley.

Software focus

Motorola's competitors generally agreed that the market is already heading for software-based radio. Texas Instruments Inc. has applied DSP to both radio tuning and digital audio processing for Eureka 147 and HD Radio, said John Gardner, marketing manager for digital radio at TI.

Eureka 147 is a pan-European digital audio broadcast standard; HD Radio, formerly known as IBOC, is a U.S. terrestrial digital radio standard.

Digitally processed radios do present some technical challenges. Gardner cited "battery life, or getting digitally processed radio to last as long or longer than analog, and cost" - bringing the costs to parity.

Still, industry watchers gave Symphony radio a fair shot at success. "If the approach had come out two or three years ago, before the advent of satellite radio, it would have made a much bigger splash," analyst Turley said. "But you could argue that Symphony is coming out at just the right time, by taking advantage of the buzz over satellite radio. The renewed interest in car radio may help rather than hurt Motorola's chances."

Subscription-based satellite digital radio services haven't exactly taken the market by storm. "I believe that satellite radio will fail. Nobody wants to pay to listen to the radio," Turley said. "Sirius is almost dead already. XM might not be far behind."

In-Stat senior analyst Michelle Abraham called Motorola's Symphony radio "interesting." Digital terrestrial radio will roll out as stations convert, she said, "while the new-architecture radios (such as Symphony) will enter the market independently of station conversions. They can be sold in areas where there are no digital stations."

Moreover, "There are no expensive changes required to the broadcasting infrastructure," Turley said. "There's no subscription fee for customers. There's no weird technology or funny antenna required. It provides a much cheaper alternative to satellite radio."

But the price of the chipset, which is sampling now at $29.95, could be an issue. "Just making the technology inexpensive enough for mainstream radios" could be a challenge, observed Abraham.

Schemes like Symphony won't necessarily be pitted against digital radio broadcast services. "We think there is a place for digitally processed AM/FM in HD Radio, certainly," said TI's Gardner, adding HD Radio boasts better sound quality.

Hansen said Motorola plans to adapt its software radio to work with different digital radio broadcast formats, once such formats become stable and services penetrate the market.

- Junko Yoshida

EE Times

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