A start-up supplier of integrated circuits has broken
through a barrier to achieving efficiency in television and set-top tuning that has
daunted the efforts of many major suppliers in the past.
The company, Plano, Texas-based Microtune Inc., said it
will begin delivering chips that support all of the functions of off-air and cable
tuner/receivers in the analog and digital modes in the second quarter of this year.
Along with integrating tuner functions, the chip provides
means of improving off-air reception while overcoming impedance mismatches in cable tuning
that can cause data signals to corrupt standard TV signals, officials said.
"This is a significant achievement," said Gene
Norrett, semiconductor-industry analyst for Gartner Group Inc.'s Dataquest.
"With all of the effort that Japanese manufacturers have put into this, you would
have thought that if it could be done, it would have been done by now."
Such integration is extremely difficult at the chip level
for several reasons, starting with the potentially devastating impact of RF leakage in the
closely packed circuitry of a microprocessor, Microtune chief technical officer John
Norsworthy said.
"People have managed to achieve some level of
integration by using two silicon chips in combination with a gallium-arsenide device, but
never on a single chip," he said.
Norsworthy added that Microtune's approach uses
conventional CMOS (complementary metal-oxide semiconductor) chip-etching technology, in
combination with standard "bipolar" techniques developed by IBM Corp.
Further complicating the integration task is the fact that
off-air tuners and cable tuners use different architectures, Norsworthy said.
Broadcast tuners in traditional TV sets use
single-conversion tuners, where the signals are modulated from the off-air frequencies to
intermediate frequencies and brought into balance to accommodate different power levels
from different channel sources.
The more expensive tuners used in cable set-tops -- while
not requiring the signal-balancing precision of off-air tuners, because the balancing
occurs at the headend -- require a dual-conversion process, upconverting each channel
before downconverting to the intermediate frequency in order to prevent leakage back into
the cable system, Norsworthy noted.
Microtune is betting on its ability to offer fully
integrated tuners at costs matching those of cable set-top tuners, Microtune CEO Doug
Bartek said. Initial shipments in quantities of 10,000 or more will be priced at about
$19.95 per chip -- twice the cost of a broadcast tuner, but just a few dollars more than
tuners used in set-tops.
"Because the cable tuner is really a component of the
cable network, cable companies can trade off tuner costs against the savings that they
afford through gains in network performance," Bartek said. "So we think that the
cost difference won't be a big issue for set-tops, whereas tuner prices are acutely
important to TV-set manufacturers."
Another strong selling point is the ability of the tuner to
overcome interference problems associated with the use of broadcast digital channels,
Bartek said.
The digital-broadcast spectrum allocated by the Federal
Communications Commission resides in the so-called taboo slots in the UHF field, where
digital signals operating at low power are supposed to reach households without
interfering with the higher-power analog signals.
But operating at lower power in the digital domain has
created problems for broadcasters, which have found that signals break up in fringe areas
of coverage where people are accustomed to receiving good quality signals off air.
As a result, Norsworthy said, some broadcasters are seeking
waivers from the FCC to pump digital signals at higher power, which could overwhelm the
ability of conventional tuners to discriminate between adjacent channels.
"We think that our device, with much better
selectivity among channels, will overcome this problem," Norsworthy said.
By supporting reception and tuning of the QAM (quadrature
amplitude modulation) and VSB (vestigial sideband) digital-broadband standard signals,
together with NTSC (National Television Systems Committee) analog, the Microtune chip also
provides a means of tightly integrating data and television feeds, officials said.
Along with cost considerations, this is a strong reason for
targeting the digital cable set-top and personal computer-TV arenas, where lead times are
shorter and the need for tight integration is greater than is the case among TV-set
manufacturers.
To accommodate PC-TV needs, the company is producing a
second chip that integrates integrated-frequency demodulation on the chips to accommodate
analog-TV reception.
"PC manufacturers don't like to have the analog
IF on the [circuit] board," Norsworthy said.
Norrett agreed that Microtune has a strong opportunity in
the cable market.
"If you're a cable set-top manufacturer running
all kinds of different signals through the box, this is an especially appealing
solution," Norrett said.
Microtune is talking to suppliers in all sectors of its
potential market base, Bartek said, declining to identify potential customers.
The company is talking to cable interests about the need to
tune signals out to 1 gigahertz in conjunction with some MSOs' plans to extend fiber
to where the full bandwidth potential of coaxial can be exploited without the degradation
effects of amplifiers.
"We're designing to 0.6 microns [circuit
dimensions], effectively, which leaves us a lot of room to add functions by going to lower
dimensions," Norsworthy said.
State-of- the-art for CMOS-integrated circuits is now in
the 0.3-micron range and approaching 0.25 microns.
