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CODAR Ocean Sensors - The Leaders in HF Radar Technology      

Inventions
 
 
CODAR HF Radar Inventions & Patents 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.
 
 
• 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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