Research

Areas of interest from the ARRC faculty, research scientists, engineers and students.
Cycle of
Innovation
Challenge / Problem Statement The University of Oklahoma has a long history in the field of radar dating back to the 1960s when radars were first used for the detailed scientific study of severe weather. The Advanced Radar Research Center (ARRC) was established in 2005 with the goal of becoming the preeminent academic institution for enhancing safety, security, environmental quality, and economic prosperity through interdisciplinary research and development of innovative radar solutions to a wide range of societal challenges.

The first step in this cycle of innovation is to understand the technological challenge at hand, and propose a cost-effective solution based on sound engineering and scientific principles.
Conceptual & System Design The ARRC has distinguished itself in recent years by fielding several operational weather radar systems with a variety of architectures, ranging from traditional, dish-based systems like PX-1000 to large-scale conformal (CPPAR) and digital beamforming (AIR) arrays. At the same time, members of the ARRC have been tackling more fundamental system-related research challenges that are paving the way towards future antenna systems for a broad range of applications. In particular, several current programs are focused on enabling large-scale advanced digital phased array beamforming architectures and transceivers that take practical C-SWaP (cost, size, weight, and power) considerations into account. System reliability is always a concern for operational systems, as is calibration and software support, and the ARRC engineers actively work with faculty and students to address these technical challenges.
As our electromagnetic spectrum becomes increasingly crowded, new techniques and technologies will be required in order to address fundamental interference issues in front-end analog electronics. For both single antenna systems and phased arrays, the ARRC researchers are working towards viable reconfigurable antenna and filter structures that can protect both front-end electronics and system-level data products from the effects of interference in both space and frequency. Because the ARRC is developing full systems from the ground up and from concept to execution, there will be numerous opportunities in the future to test these interference mitigation techniques in practical systems.
  • Advanced digital architectures
  • Adaptive & Reconfigurable transmission
  • Low-C-SWaP
  • System Reliability
  • Expedited algorithm and supporting software design
Faculty members related to this area:
  • Boonleng Cheong
  • Caleb Fulton
  • Nathan Goodman
  • Robert Palmer
  • Jorge Salazar-Cerreño
  • Mark Yeary
  • Guifu Zhang
  • Rockee Zhang
RF Components

"The whole is greater than the sum of its parts." - Aristotle

Response: "The whole is not functional without its parts." - Sigmarsson

When it comes to radar and communications systems, the RF hardware represents a significant portion of the parts. Therefore, in order to advance the state-of-the-art system design, RF component research is very important. These include passive components such as attenuators, combiners, couplers, and filters and active components such as amplifiers, mixers, phase shifters, and switches. Currently there is a lot of focus on reconfigurable RF components for the next generation of agile, spectrum-efficient radio systems.

Research in the ARRC covers all aspects of RF component design leveraging advanced circuit theory and electromagnetics. Operating frequencies currently range from VHF up to W-band on platforms like traditional circuit boards such as laminates and ceramics. Additionally, semiconductor microfabrication allows for unique chip-scale designs. Examples of recent/ongoing RF-components-related projects include:

  • Integrated filters/antennas (filtennas)
  • RF phase shifters for antenna arrays
  • Phase-change material RF switches
  • Frequency selective surfaces (FSS)
  • Advanced packaging techniques
  • Multi-layer RF circuit boards
  • High-efficiency amplifiers
  • 3D printed components
  • Reconfigurable filters
Faculty members related to this area:
  • Caleb Fulton
  • Jorge Salazar-Cerreño
  • Hjalti Sigmarsson
  • Rockee Zhang
EM Fields & Antennas

Building on a legacy of applied electromagnetics research centered around dish-based radar systems and radar cross-section (RCS) engineering, the ARRC is now focused on advanced antenna and wave propagation research for a variety of application spaces.

Modern radar systems make use of phased arrays, and emerging weather radar systems are additionally dual-polarized. Much of the ARRC's current research efforts are addressing engineering challenges with the marriage of these two technologies for weather spaces, while simultaneously pushing array-based technologies in general (including reflectarrays) for radar and communications applications.

At the same time, much of the ARRC's current applied electromagnetics research goes far beyond radar to include other applications and challenges. The spectrum crisis has spurred development of multi-function, multi-frequency, and ultra-wideband antennas to enable enhanced spectrum efficiency. ARRC researchers are developing antennas with frequency tunability and pattern reconfigurability that directly address the requirements of future, spectrally-diverse systems. Finally, the ARRC's numerous manufacturing and testing resources are increasingly enabling the rapid prototyping of previously unmanufacturable structures using additive manufacturing and multi-layered circuit board structures.

Some specific areas include:

  • Dual-polarization phased array elements
  • Novel calibration methods
  • Reflectarrays
  • Multi-band antennas, UWB antennas, tunable antennas, RFID
  • Pattern reconfigurable antennas
  • Wave propagation
  • RCS engineering
Faculty members related to this area:
  • Caleb Fulton
  • Jessica Ruyle
  • Jorge Salazar-Cerreño
  • Guifu Zhang
  • Rockee Zhang
Backend Systems & Embedded Software Next, backend systems are connected to the antennas, and these mostly digital systems are governed by embedded software. These backend systems support transmit and receive functions. A combination of custom RF circuits, analog circuits, and/or digital circuits are used for transmission and reception. For instance, in some highly modern applications, waveform samples may be stored within the memory of a field programmable gate array (FPGA) and uploaded to a digital-to-analog converter (DAC) prior to being amplified and transmitted through an antenna. While in other applications, custom digital receivers are being designed to reduce the size, weight, and power needed for current and next-generation digital beamforming radars. For instance, ARRC's Atmospheric Imaging Radar (AIR) uses 36 in-house designed digital receivers. As mentioned previously, the flexible digital front ends are governed by embedded software. This software controls digital waveform generation techniques, digital beamforming (both on transmit and receive), and state-of-the-art digital calibration methods. For instance, the ARRC's Cylindrical Polarimetric Phased Array Radar (CPPAR) employs advanced digital calibration techniques for corrections that must be made for mutual coupling and other electromagnetic effects associated with its specific antenna design. In summary, backend systems and embedded software are key drivers for next-generation radar innovation.
Research areas that utilize backend systems & embedded software include:
  • Software-defined radar
  • Custom digital transceivers
  • Fully digital up/down conversion, polyphase filtering, decimation, etc.
  • Low-latency data routing
  • Real-time processing
Faculty members related to this area:
  • Boonleng Cheong
  • Caleb Fulton
  • Mark Yeary
  • Rockee Zhang
Fabrication & Test Facilities The Radar Innovations Laboratory (RIL) has all the necessary facilities and equipment to allow researchers to rapidly go from an idea to a conceptual design to a fully functional prototype. This is accomplished by a combination of a wide range of simulation, fabrication, and testing capabilities.

Simulations: The available circuits and electromagnetics simulation tools include: ADS, ANSYS HFSS, CST, FEKO, and Microwave Office.

Fabrication: The RIL has in-house fabrication capabilities for creating multi-layer printed circuit boards. These capabilities include: circuit board plotting, lithography, thru hole plating, and pick-and-place. Rapid prototyping of electromagnetically functional components is achieved via metallized 3D printed parts, both using stereolithography and fused deposition modeling. Fixtures and larger parts are created in a machine shop. Finally, entire systems can be assembled and prepared for fielding in a high-bay assembly area.

Testing: The heart of the RIL consists of several anechoic chambers and measurement facilities. Far-field measurements down to 300 MHz and up to 50 GHz; planar, cylindrical, and spherical near-field scanning; environmental antenna testing, and direct mutual coupling measurements are available. Furthermore, the RIL contains a full range of the standard high-frequency measurement equipment from Keysight, Tektronix, Copper Mountain, and many others.

  • Precision anechoic chambers
  • High-bay integration facilities
  • Environmental chamber for temperature cycle testing
  • Machining, fabrication, and prototyping
Faculty members related to this area:
  • Boonleng Cheong
  • Caleb Fulton
  • Robert Palmer
  • Hjalti Sigmarsson
  • Mark Yeary
  • Guifu Zhang
  • Rockee Zhang
Fielded Radars The ARRC supports several radar systems. As most of the key components are developed in-house, newly developed techniques can be implemented and tested on these radar systems assess the performance in practice. The AIR is one of many them has been used extensively to investigate adaptive beamforming techniques and pulse compression waveforms. Besides engineering research and development, the ARRC also deploys these radars for meteorological and hydrological missions. As an example, the PX-1000 radar was deployed in Colorado in the fall of 2014 and 2015 to help cover forest burned scars, which are prone to flash floods and landslides. These are also areas of with insufficient radar coverage from the existing weather radar network. Operated remotely, forecasters and emergency meteorologists responsible for the area were able to use the real-time data from the radar to monitor the weather conditions of the area.
Radar platforms that ARRC supports include:
  • Mobile weather radar
  • Advanced phased array radar
  • Airborne radar
  • Stream radar for hydrological studies
Faculty members related to this area:
  • Michael Biggerstaff
  • David Bodine
  • Boonleng Cheong
  • Caleb Fulton
  • Pierre-Emmanuel Kirstetter
  • Robert Palmer
  • Mark Yeary
  • Tian-You Yu
  • Guifu Zhang
  • Rockee Zhang
Click here for more information about the ARRC radar systems.
Signal Processing The ARRC has strong expertise in signal processing, covering a wide range of topics such as waveform design, adaptive array processing, compressive sensing, digital pre-distortion, image formation, clutter and interference cancellation, and multi-radar, multi-sensor fusion. One of our goals is providing innovative solutions for optimizing radar performance in terms of resolution, accuracy, interference and clutter mitigation, data quality, and multi-functionality.. Another strength is in the development of signal processing techniques tailored to emerging radar technologies such as cognitive and adaptive radar, multi-mission phased array radar (MPAR), all-digital and polarimetric phased arrays, and simultaneous SAR-GMTI.. Development of detection and tracking algorithms for both weather and defense, security, & intelligence (DSI) applications is another emphasis in the ARRC, where artificial intelligence techniques such as fuzzy logic, neural networks, genetic algorithms, and Bayesian frameworks are often used. Leveraging on GPU technology, ARRC's physics-based radar simulator can produce radar signals based on realistic target environments; therefore, the simulator is ideal for testing and verification of signal processing techniques. Signal processing research and algorithm development are further supported by the ARRC's innovative hardware platforms and deployable systems, which have the flexibility to be used as testbeds in a variety of configurations.
  • Cognitive and adaptive radars
  • Waveform design
  • Physics-based radar simulation
  • Multi-radar, multi-sensor fusion
  • Adaptive array processing
  • Fuzzy logic and neural networks
  • Clutter mitigation
  • SAR, ISAR and GMTI
  • Digital pre-distortion
  • Genetic optimization
Faculty members related to this area:
  • Boonleng Cheong
  • Caleb Fulton
  • Nathan Goodman
  • Robert Palmer
  • Alexander Ryzhkov
  • Sebastian Torres
  • Mark Yeary
  • Tian-You Yu
  • Guifu Zhang
  • Rockee Zhang
Applications

The vigorous development of radar technologies in the ARRC are driven not only by practical applications and needs, but also curiosity in fundamental science, engineering, and national safety. The ARRC applies its innovative systems and technologies to various fields of weather, climate, water, aeroecology, aviation, and DSI. The overarching goal of applying these technologies to the observation of natural and man-made hazards is to reduce their risk through better understanding of the phenomena, improved representation and data assimilation in numerical prediction models, and effective risk communication. Example topics include tornadoes and severe weather, radar hydrometeorology, climate and climatology, precipitation microphysics and dynamics, quantitative precipitation estimation (QPE) with ground-based, space-based radars, and multi-frequency radars etc.

Ensuring the safety and security of our nation comprises a multi-faceted radar challenge involving ever-changing technologies and strategies. The ARRC has expertise in DSI-related radar technologies including electronics and digital architectures for phased-array antennas, low-profile antenna design, novel materials for tunable circuits, adaptive radar measurement and processing, and other emerging radar system concepts. For instance, ARRC's portfolio includes dismount and slow-moving target detection, extremely wide-area search and track, target classification, high-resolution imaging, and exploitation of polarimetric radar.

  • Tornadoes and other severe weather
  • Radar hydrometeorology
  • Climatology and climate
  • Precipitation microphysics and dynamics
  • QPE with ground-based and space-based radars
  • Radar data assimilation and forecasting
  • Natural hazard prediction and disaster risk
  • Aeroecology
  • Multi-frequency radars
  • Dismount and slow moving target detection
  • Extremely wide area search and track
  • Target classification
Faculty members related to this area:
  • Michael Biggerstaff
  • David Bodine
  • Boonleng Cheong
  • Caleb Fulton
  • Nathan Goodman
  • Yang Hong
  • Pierre-Emmanuel Kirstetter
  • Robert Palmer
  • Alexander Ryzhkov
  • Mark Yeary
  • Tian-You Yu
  • Guifu Zhang
  • Rockee Zhang
Knowledge / Decisions After the cycle of innovation is complete with the design and development of advanced antennas, RF components, radar systems, field tests, algorithm development, data interpretation, etc., a more complete understanding of the scientific and/or engineering challenge is obtained. Often, this understanding is disseminated through the academic literature. Many of the ARRC's publications are provided on the Publicaiton page of the website.

Click here for the ARRC Publications.
Preface