On 12/01/2012 05:05 PM, Mark Kahrs wrote:
Very interesting topic. So, it appears that UrsaNav bought a pair of
companies that have interesting IP. In particular, CrossRate has a few
interesting patents -- this may be the most relevant:
United States Patent Application 20080144744:
A system for demodulation of the Loran Data Channel transmitted over the
Enhanced Loran (eLoran) system including a quadrature filter. The
quadrature filter calculates the real and quadrature phase components of a
received ninth pulse. The resultant components are used to obtain the angle
of the ninth pulse. This angle is then compared with a set of pre-tabulated
angles/symbols that are calculated using the same quadrature filter on
thirty-two different simulated ninth pulses. The closest angle match gives
the corresponding symbol. Such twenty-four symbols make up a single Reed
Solomon encoded message. This message is then passed through a Reed Solomon
decoder and the transmitted message is obtained.
Do read the paper, as it proposed to remove the ninth pulse and use a
OFDMA modulation for the data-part while the PNT part would be modified
variants of the traditional LORAN-C pulses. This patent would those not
be relevant for the proposed scheme.
Also, UrsaNav teamed with Nautel, noted LF amplifier designer for this
system. Interesting.
Considering that they intend to change pulse-shapes and even add a
complete new modulation technique, the transmitters need to support it.
Cheers,
Magnus
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