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Unique and patented CODAR
features give SeaSondes® the distinction of being
the only HF radar commercially available today as a truly complete
operational ocean monitoring system.
All required radar hardware & software are designed and implemented by CODAR
-- No dependence on third parties for ANY elements. |
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• CODAR Invents River
Version of Ocean-Monitoring SeaSondes -- the
RiverSonde:
Barrick, D. E., C.C. Teague & P.M. Lilleboe (2008), Systems and methods for monitoring river flow parameters using a VHF/UHF radar station, U.S. Patent Application 20090195437
Applying SeaSonde principles for open-ocean surface currents to small-scale river
flows
has something old but also something new -- it's not just a simple scaling of
frequency
and antennas by a factor of 20. Operation at a higher frequency (~430 MHz) is
necessary because the water roughness scales are much smaller. But at the higher
frequencies, the crossed-loop SeaSonde antenna design is not appropriate; so
CODAR
replaced it with a compact three-array Yagi unit. This employs something new
-- a
combination of MUSIC direction finding as well a beam forming. Dealing with aliasing
of
the Bragg echoes that does not happen with SeaSondes is part of the latest
invention. To operate within populated areas where this technology is important,
the
RiverSonde reduces output power to less than a watt, while consuming very little
input
power. The entire electronics sensor unit -- including antennas -- are mounted
on a
single post.
Click here to >> Download
Document << (approx. 172K)
• CODAR Invents a
Compact Beam-Forming Phased Array Mounted on a Single
Post:
D.E. Barrick, P.M. Lilleboe (2005), Circular Superdirective Receive Antenna Arrays, U.S. US 6 844 849
Phased array antennas that can form and scan narrow receive beams also offer
higher
directive gain, but require huge expanses of coastal land, sometimes hundreds
of
meters in length. CODAR has adapted superdirective antenna principles to create
circular arrays mounted on top of a post, out of reach, to do the same job. These
are a
tiny fraction of a wavelength, and so are the ultimate in compactness. Yet they
have
adequate efficiency so there is no decrease in signal-to-noise ratio over much
larger,
conventional linear arrays. Many applications suggest themselves for this invention.
Click here to >> Download
Document << (approx. 816K)
• CODAR Pioneers in Estimating Total Vectors when
Two-Site Data Are
Unavailable: Normal Modes:
Barrick, D.E. (2003), Synthesis of total surface current vector maps by fitting normal modes to single-site HF radar data, U.S. Patent 6 590 523.
Large area sectors of the sea can usually be seen by only one radar. Often, land
protrusions block visibility to even a single radar. By conventional wisdom,
such situations imply no total vectors. When this happens within nearly enclosed
bays, CODAR has adapted Normal Mode Analysis, a hydrodynamics-based method, to
fit directly to all available radial velocities, so as to produce continuous
total vector fields within the bay.
Click here to >> Download
Document << (approx. 1.1M)
• CODAR Invents GPS Modulation Synchronization So Multiple
Radars
Operate Simultaneously on Same Frequency:
D.E. Barrick, P.M. Lilleboe, and C.C. Teague (2001), Multi-station HF FMCW radar frequency sharing with GPS time modulation multiplexing, U. S. Patent 6 856 276
Proliferation of HF radars worldwide means that multiple stations can
no longer obtain approvals for separate operating frequencies. CODAR solved this
problem by employing worldwide satellite GPS (global positioning system) time
signals to synchronize the modulation timing of multiple HF FMCW radars. This
minimizes HF radar spectral occupancy with no interference penalty among SeaSondes
simulataneously sharing the same channel.
Click here to >> Download
Document << (approx. 716K)
• CODAR Invents and Applies Bistatic
Augmentation to SeaSonde Current-Mapping Radars:
D.E. Barrick, P.M. Lilleboe, B.J. Lipa and J. Isaacson (2001), Ocean surface current mapping with bistatic HF radar, U. S. Patent 6 774 837
This breakthrough invented at CODAR allows simple, tiny, low-cost, transmitter
units to be added to existing SeaSonde backscatter radars, converting a single
radar into many. Operating simultaneously with the GPS synchronization described
above, the same point on the sea is illuminated by multiple transmissions, the
echoes from which are all processed in the same PC-based receiver unit. This
extends the coverage distance and improves the accuracy and robustness of standard
backscatter
SeaSonde networks.
Click here to >> Download
Document << (approx. 1M)
• CODAR Discovers and Implements MUSIC Direction-Finding
Algorithm
That Replaces Least Squares:
D. E. Barrick, and B. J. Lipa (1999), Radar angle determination with MUSIC direction finding, U. S. Patent 5 990 834
As much as the CODAR least-squares direction-finding algorithm revolutionized
HF radar current mapping, it had a drawback due to the linear dependence among
multiple signals from different directions. This was eliminated by application
of a specially designed MUSIC (MUltiple SIgnal Classification) algorithm that
actually capitalizes on this linear dependence, thereby providing totally robust
performance in complex signal environments.
Click here to >> Download
Document << (approx. 980K)
• CODAR Invents Pulsing Format with FMCW Waveform That
Allows Its Use with Backscatter Radars:
D.E. Barrick, B.J. Lipa, P.M. Lilleboe, and J. Isaacson (1994), Gated FMCW DF radar and signal processing for range/Doppler/angle determination, U. S. Patent 5 361 072
When radar transmitter and receiver are co-located (i.e., backscatter), pulsing
must be applied to prevent destruction of dynamic range or damage to receiver.
CODAR invented a pulsing format that accomplishes this, while not introducing
aliasing or blind zones encountered with all prior waveforms and retaining the
highly efficient, low-data-rate advantages
of the original FMCW signal.
Click here to >> Download
Document << (approx. 1.6M)
• CODAR Creates Crossed-Loop/Monopole Antenna
System:
Carr, a CODAR employee invents the first crossed-loop / monopole antenna. Carr, A.C. (1984), Three-element antenna, U.S. Patent 5 361 072 Barrick and his partners reduce its size to a tiny box. U.S. Patent 5 361 072
Click here to >> Download
Document << (approx.
1.6M)
Three antennas are combined inside a tiny box, mounted on single
pole out of reach, on offshore rig, or building roof. Has demonstrated
optimal efficiency and better accuracy for current mapping
than phased-array beam-forming or older square NOAA direction-finding
array of preceding patent.
• CODAR Develops and Tests Objective Least-Squares Algorithm for Current Mapping:
[Lipa, B.J. and D.E. Barrick (1983), Least-squares methods for
the extraction of surface currents from CODAR crossed-loop data: Application
at
ARSLOE, IEEE J. Oceanic Engr., vol. OE-8, pp. 226-253]
This robust,
objective algorithm overcomes the arbitrary, ambiguous "closed-form" algorithms
developed at NOAA for direction finding. It allows objective statistical testing
that selects among signal hypotheses. The result is increased accuracy while
eliminating ambiguities, so as to map complex current features better than the
older, more cumbersome phased array antenna systems.
• CODAR Invents Radar Direction Finding to Replace Conventional Phased-Array
Antenna Beam Forming:
Barrick, D.E. and M.W. Evans (1979), CODAR: coastal HF radar for real-time current mapping, U. S. Patent 4 172 255
This breakthrough got rid of the large, cumbersome, expensive, conventional
phased-array
antennas that had hindered widespread HF radar acceptance.
Click here to >> Download
Document << (approx. 720K)
• CODAR Staff Invents Highly Efficient
Radar FMCW Waveform for Low-Data-Rate PC Digital Processing with High-Bandwidth Signals:
[Barrick, D.E. (1973), FM/CW radar signals and
digital processing, NOAA Tech. Report ERL 283-WPL 26]
Until
this invention, high pulse power and high data rate processors were required for
radars to achieve great ranges and good spatial resolution. The FMCW (frequency-modulated
continuous wave) signal with receiver demodulation and low-rate PC digital processing
was the breakthrough that leap-frogged ahead two generations to the present robust,
low-cost, efficient SeaSondes.
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