The zero-IF revolution

The zero-IF revolutionMelanie Reynolds
Zero-IF tuner chips will offer set-top box designers cost and space savings according to the chip manufacturers.
Zero-IF (zero-intermediate frequency) technology removes the need for any IF stages, such as a SAW (surface acoustic wave) filter, by processing the RF signal directly from the satellite dish into baseband.
At the Cable and Satellite show last week, zero-IF products were talked about and demonstrated by LSI Logic and Infineon Technologies, the latter working with VLSI Technology.
LSI Logic says its L64733 zero-IF tuner IC and L64734 QPSK (quadrature phase shift keying) demodulator IC perform the functions previously done by up to four chips and reduces the external component count.
“Zero-IF is quite a revolutionary phase in the front end market,” said Kenroy Francis, director of set-top box development at LSI Logic. “It’s developed with the mindset to reach the next price point down.”
LSI worked with other companies on the ICs using known technology to come up with a solution which it believes splits the functions performed in a sensible way between the two chips.
The chips are being aimed at customers who have the skill and experience needed to design with RF. “It’s not a digital circuit, it’s still RF that we’re dealing with. You can’t just slap it down,” explained Francis.
Meanwhile, Infineon Technologies is offering its own zero-IF chip, the TUA6100, which can be combined with VLSI Technology’s VES1993 digital decoder.
This combination, the firms claim, offers a competitive front end solution to set-top box and integrated digital TV manufacturers.
The TUA6100 has common interfaces like I/O for an external baseband filter and I/Q output to the QPSK demodulator chip. It can support I/Q outputs from 1 to 45Msymbols/s. The VES1993 integrates A/C converters, anti-aliasing filters, QPSK decoding and forward error correction on a single chip.
Both LSI and Infineon’s chips are designed to support the DVB-S and DSSbroadcast systems.


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