[opendtv] Mobile 8-VSB from Linx/Micronas
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: "OpenDTV (E-mail)" <opendtv@xxxxxxxxxxxxx>
- Date: Wed, 10 Nov 2004 10:32:19 -0500
This article could not have been more a propos.
Micronas is the German company that bought Linx.
Make sure you read to the end of the article.
Because 8-VSB is a single-carrier system, any
diversity tuning technique ought to be even more
beneficial to 8-VSB, to combat deep notches in
the received spectrum, than it is for COFDM.
In COFDM, the redundancy offered by the FEC
spreads each bit transmitted over a number of
different subcarriers, which are scattered
throughout the frequency band. So that helps
survive deep nulls even without diversity
tuning. But with 8-VSB, the equalizer alone is
often unable to compensate for very deep nulls.
You can't create energy where none exists.
But since these deep nulls tend to be very
localized, if two antennas are available at the
receiver, any antenna spacing at all (e.g. one
wavelength) will usually be enough to get useful
energy out of one antenna where a null exists at
the other antenna.
I think that diversity antennas combined with use
of the training sequence is what will allow 8-VSB
to work in mobile scenarios.
If you want to use the link, remember to remove
any "2D" or "3D" characters that follow the
"equals" sign in the URL.
Bert
--------------------------------------
Micronas unveils modulator for mobile DTV
By Junko Yoshida , EE Times
November 10, 2004 (5:41 AM EST)
URL: http://www.eet.com/article/showArticle.jhtml?articleId=3D52600424
MUNICH, Germany - Seeking to solve mobile reception
problems associated with digital TV signals in
automotive applications, Micronas has unveiled a new
Codfm (coded orthogonal frequency-division multiplex)
demodulator IC.
The chip uses diversity technology licensed by
Micronas from Rohde & Schwarz, based here, a producer
of communications and test and measurement equipment.
Micronas said at the Electronica show here that is
has become the first chip company to license the
patented diversity technology called Maximum Ratio
Combining (MRC).
Diversity techniques improve signal reception
performance by using two or more antenna/demodulator
combinations. MRC uses information from each
demodulator and obtains for each data-carrier of the
signal the best possible transmission quality.
Micronas added to MRC its own digital filtering
algorithms that combine a channel estimator with
adaptive prediction and a diversity interface. "We've
turned MRC into a true adaptive MRC," said Wladimir
Punt, system marketing manager at Micronas. "The
adaptive MRC can give better confidence in the channel
analysis," resulting in strong Cofdm demodulation
behavior in dynamic environments, he added.
The European modulation scheme adopted for its
DVB-T-based terrestrial digital TV standard is believed
to be better suited for mobile TV reception compared to
8VSB used for U.S. terrestrial digital TV. "It's
largely because DVB-T embedded helper information
inside broadcast signals," said Punt, to cope with
severe channel conditions.
But even the DVB-T standard has problems when its
signals need to be received in a fast-moving car in
downtown areas with many tall buildings. When receiving
many multipath signals, a car TV receiver suffere from
deep fading or complete cancellation of the desired
channel. Further, the movement of the receiver causes
so-called Doppler effects, distorting the DVB-T channel
information.
Micronas plans to launch its new diversity demodulator
with adaptive MRC in the first half of 2005. "We will
have our prototype designed into a car for field
testing next year," said Punt. "You will see our chip
in a high-end car in 2006."
Micronas is also planning to apply adaptive MRC to the
company's 8VSB demodulator chip used for U.S. digital
TV broadcasts.
Copyright 2003 CMP Media
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