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Conexant takes plunge for DVB-S2 wave

Posted: 16 Sep 2004 ?? ?Print Version ?Bookmark and Share

Keywords:dvb? conexant? satellite? set-top box? ldpc?

When the digital video broadcast for satellite version 2 (DVB-S2) specifications emerged last year, it was not the best of news for established silicon vendors serving the STB market. Changes in the specification forced a new round of complex silicon development for the set-tops.

The changes were driven by service providers' need for more bandwidth. But to play in the new STB market, silicon vendors found that they would need to design a new demodulator and a new low-density parity check (LDPC) error-correction unit. That is no small task. STMicroelectronics bared that it was working on such chips.

But Conexant Systems Inc. announced live silicon for DVB-S2: the CX24116. The chip includes a demodulator and an FEC unit, both compliant with the new specification as defined by the Digital Video Broadcasting Project consortium.

On the front-end, the chip required a new pair of fast 8bit ADC to handle the incoming analog I/Q signals and pass them to the demodulator. The demodulator handles both quadrature phase-shift keying (QPSK) and 8PSK modulation schemes at symbol rates of up to 30Msymbols/s.

The FEC block implements a concatenated LDPC/BCH (Bose-Chaudhuri-Hocquenghem) error-correction scheme. Both the decoder and the FEC block required new designs, said Conexant product director Manjit Gill.

In addition to the functional blocks, the chip includes an industry-standard 8bit microcontroller, which acts as a programmable state machine, to implement fast signal-acquisition algorithms, and which executes the driver code for the chip. By moving the driver on-chip, Conexant has simplified the external driver interface and reduced the amount of real-time work that must be done by the STB's control CPU, Gill said. That frees the set-top's CPU for other tasks such as graphics.

The CX24116, produced in a 130nm CMOS process by TSMC Ltd and packaged in a 100-pin exposed thin-quad flat pack, is sampling now.

- Ron Wilson

EE Times

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