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[hfsig] VMSK arisen again in new shape and form?

Anthony.N.Martin at selex-comms.com Anthony.N.Martin at selex-comms.com
Thu Dec 1 13:55:16 UTC 2005



This is a post I made on another forum back in July.
I have heard some suggestions that the parentage of VMSK
and XG are related. It is not certain that the modulation patented
by XG is that which they are actually using in demonstrators.
.....


>> http://www.xgtechnology.com/index.html

BFSK? What's BFSK? Real or snake oil?

Spectrum plot suggests narrow bandwidth. Is it fully modulated?
Given the high data rate, where are the sidebands?

If the sidebands are widely spread and much lower than the carrier,
there's so much power wasted in the carrier how can it have sensible
BER/SNR?

I smell snake-oil.

Nice "meet the team" page at XG. Where are the RF engineers...?

No details of BFSK on the website. A little light research.

US Patent 6901246   May 31, 2005
inventor Bobier, assignee XG Technology

Suppressed cycle based carrier modulation using amplitude modulation

A sinusoidal RF carrier is modulated for the transmission of digital binary
data streams through the amplitude suppression of carrier wavelets. These
wavelets are defined between zero crossover positions representing zero
energy locations. This modulation is accomplished when the carrier is
slightly
amplitude modulated with a modulation signal that is equal in frequency to
the
carrier itself and the modulation always begins or ends upon the exact zero
voltage crossing point of the RF cycle phase. The modulation is applied as
a slight shift of the amplitude of any single cycle, each cycle
representing a
single bit of data. A single cycle of RF will either represent a "1" or "0"
depending upon the amplitude of the cycle, relative to other adjacent
cycles
in the same carrier.


It cannot be correct that a massive carrier with tiny AM and extremely
short
symbol periods has the SNR vs BER characteristics proposed. Way too much
energy is wasted in the carrier, and the information is in the sidebands,
which are
small. Or is it time to fetch out the old AM rigs, and turn down the mod
depth as
much as you can!? Looks in need of a sound debunking, like Phil Karn did
with
VMSK.  http://www.ka9q.net/vmsk/

Note the sidebands peak at 1.5 * Fc, which is outside the spectrum plots.

Hmm, so where do they consider the noise bandwidth to be when
measuring BER vs SNR? That is the killer question.


May one ask why one can get a patent for ASK from the USPTO?


Also from Bobier:
US Patent 6,405,058  Wireless high-speed internet access system allowing
multiple
                        radio base stations in close confinement
US Patent 6,275,196  Parabolic horn antenna for wireless high-speed
internet access
USPTO database is dumping most www connects on the floor at the moment.
Pity they didn't do that more with patent applications.


Ant M1FDE

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