• CODAR Invents an End-to-End Tsunami Warning System for HF Radars:
D.E. Barrick, B.J. Lipa, J. Isaacson (2016), Coastal HF Radar System for Tsunami Warning, U.S. Patent Application 15/140,325
Although the capability of detecting tsunamis with coastal HF radars was discovered and published by Barrick in 1979, this was just the beginning of evolution toward a useful warning system. Capturing signals from actual tsunamis in 2011 enabled our development of a pattern-recognizer that would pull tsunamis out of background currents and noise. False alarms had to be dealt with and mitigated. So an end-to-end system was developed that filters by a variety of means in order to reduce false alarms and optimize tsunami detection. This led to a partnership with NOAA to integrate unique HF near-field warnings into their Tsunami Warning Centers.
• CODAR Invents Negative Pseudo-Range Processing with Multi- Static FMCW Radar:
W.C. Rector, D.E. Barrick, B.J. Lipa, H.. Aguilar Jr. (2016), Negative Pseudo- Range Processing with Multi-Static FMCW Radars to Double the Quantity and Quality of Information, U.S. Patent 9 442 188, China Application 2015 0112466.5, Japan Application 2015-039784, Republic of Korea Application 10-2015-0034653
CODAR SeaSondes have a unique way of determining target range from their FMCW signals. Range from target time delay is transformed by our linear signal chirp into a frequency offset proportional to range. Because of the complex numbers used in describing the signals, we also get numbers that correspond to negative range, which is normally meaningless for radar users. However, we have discovered utility to these negative ranges. For bistatic geometries, it doubles the amount of joint radar area coverage possible. In addition, it can be useful for removing radio interference from the positive range cells where sea echo and ship echoes may be contaminated.
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• CODAR Invents Combined Transmit/Receive Single-Post Antenna for HF/VHF Radar:
D.E. Barrick, P.M. Lilleboe (2013), U.S. Patent 8 447 065 (previously U.S. Patent 8 031 109), China Patent 2010 10231472.X
CODAR established our hallmark feature that broke from the past and all our competitors. We eliminated the large phased-array antennas that occupy hundreds of meters of ocean property in favor of two simple single antennas for transmit and receive that each take only a couple meters space. Because even that was inconvenient in certain cases, we found a way to combine these two into a single-mast dome-mounted unit. Offered for frequencies above 10 MHz, this can be enclosed by a security fence or mounted on a building rooftop. All of this is done at reduced cost and no penalty in sensitivity or performance over the huge phased arrays of yesteryear.
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• CODAR Invents River
Version of Ocean-Monitoring SeaSondes -- the
RiverSonde:
Barrick, D. E., C.C. Teague & P.M. Lilleboe (2010), Systems and methods for monitoring river flow parameters using a VHF/UHF radar station, U.S. Patent 7 688 251, China Patent ZL 2008 100950935, Japan Patent 5460066.
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.
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• 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. Patent 6 844 849, Germany Patent 102004 033 375, Japan Application 2004-202574, UK Patent 2403853
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.
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• 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.
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• CODAR Invents GPS Modulation Synchronization So Multiple
Radars
Operate Simultaneously on Same Frequency:
D.E. Barrick, P.M. Lilleboe, and C.C. Teague (2005), Multi-station HF FMCW radar frequency sharing with GPS time modulation multiplexing, U. S. Patent 6 856 276, Germany Patent 10231660, Japan Patent 4036697, UK Patent GB2393871
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.
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• CODAR Invents and Applies Bistatic
Augmentation to SeaSonde Current-Mapping Radars:
D.E. Barrick, P.M. Lilleboe, B.J. Lipa and J. Isaacson (2004), Ocean surface current mapping with bistatic HF radar, U. S. Patent 6 774 837, Germany Patent 10231661, Japan Patent 4043878, UK Patent GB2382481
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.
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• 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.
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• CODAR Invents Crossed-Loop/Monopole Antenna System with FMCW Waveform Pulsing to Optimize Use with Backscatter Radars:
D.E. Barrick, B.J. Lipa, P.M. Lilleboe, and J. Isaacson (1994), Gated FMCW HF radar and signal processing for range/Doppler/angle determination, U. S. Patent 5 361 072
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 beamforming or older square NOAA direction-finding array of preceding patent. 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.
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• 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.
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• 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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