Agere Systems Inc has announced technical details and the first samples of broadband receiver chip sets for a planned satellite digital audio radio service in North America
The eight-chipset is being initially aimed at US automotive applications after three years of joint development by Agere (formerly Lucent Microelectronics) and Sirius Satellite Radio Inc. New York-based Sirius plans to start up its subscription-based satellite radio services by the end of 2001 with up to 100 channels of audio entertainment programming.
Agere said it has begun shipping engineering samples of the complex chip set to seven consumer electronics manufacturers: Alpine, Clarion, Delphi Delco, Jensen, Kenwood, Panasonic, and Visteon. Volume production of the satellite radio receiver chips is scheduled to begin early this autumn, using 0.25-micron CMOS and BiCMOS processes at a joint-venture foundry fab operated by Agere and Chartered Semiconductor Manufacturing Pte Ltd in Singapore.
"Our approach has been to use a true broadband receiver architecture," said Rob Franzo, director of Agere's automotive products group--which is part of the companies new business initiative. "While some might say it shouldn't take this number of eight devices, it was done to validate the system and make sure there were no compromises." The architecture is also set up to enable rapid integration of the set in the near future with the baseband portion of the receiver being packed on a single IC.
But first, the development project focused on providing highly reliable and clear reception of the satellite broadcasts oin moving vehicles, using the 12.5MHz spectrum licensed by Sirius for radio service across the entire country. To do this, the system uses and processes three signals simultaneously. The design combined the use of coded orthogonal-frequency division multiplexed (COFDM) for signals broadcast from ground atennas, and two time-division multiplexed quadrature phase shift keyed (TDM-QPSK) bands for reception from signals sent from three satellites.
"The system transmit signal in frequency time space and modulation diversity, which results in very good performance against blockage and fading," explained Franzo, referring to the difficulties of maintaining high-quality digital audio in moving vehicles across the entire United States.
"No information is destroyed or thrown away in the channel until it reaches the concatenated decoder chain," he said, explaining the broadband receiver architecture. "That provides a lot of flexibility in terms of the roadmap for integration of the chip set and future design iterations for our products following this initial one."
Agere is not releasing pricing information on the current eight-chipset designs. The radio receiver manufacturers licence the technology from Sirius, which includes the chipset into the package as part of its efforts to launch the satellite radio service.
While subscription-based nationwide radio is a new concept, the market potential is huge, according to Agere and its partner Sirius. In the United States there are more than 200 vehicles travelling on roads, and Sirius hopes to entice listeners with 50 channels of commercial-free music and 50 channels of news, sports, talk, comedy, and children's programming.
The idea is to give travellers on the highway something to listen to other than the same old set of CDs or local radio programs, Franzo said.
To deliver high-quality digital audio, the Agere chipset first processes three including sets of signals that contain the same information (two being time-division multiplexed from the satellites, and the other frequency-division multiplexed from the terrestrial antennas). The TDM and COFDM signals are processed and filters by radio frequency (RF) and intermediate frequency (IF) chips to an IF output of 75MHz. An analogue-to-digital converter undersamples the 75MHz IF to 60 megasamples for a digital image with 15MHz of bandwidth of encoded signals (two TDM and one COFDM).
The signals are then digitally filtered and demodulated before being combined into for 100 channels of radio signals by a maximum ratio combiner. A concatenated decoder chain IC is used to select a specific channel for playing through a digital audio processor--which contains an Agere 1600 digital signal processor (DSP) core and an ARM RISC processor. In addition to the eight ICs in the chip set, the radio receiver will use DRAM, SRAM and flash memory chips.
Agere is not announcing a product roadmap at this time, but Franzo said it was possible to integrate an entire baseband receiver on a chip using finer process geometries in the next 16 to 18 months.
--J. Robert Lineback
