Advanced Radar Research Center, University of Oklahoma
3190 Monitor Ave.
Norman, OK 73019
U.S.A.
http://arrc.ou.edu
Norman has a long history of radar research, development, and application among the Universityof Oklahoma (OU), National Oceanic and Atmospheric Administration (NOAA), and local industrial
partners. Under the leadership of President Boren, the Strategic Radar Initiative (“Radar Initiative”)
was started in 2003. Soon thereafter, scientists and engineers from Norman worked together todevelop an ambitious plan with the goal of developing a core of resident intellectual leaders andstudent talent unsurpassed in the world. Under the strategic Radar Initiative, existing and new
hired faculty members were united in 2004 to form the interdisciplinary Advanced Radar ResearchCenter (ARRC, http://arrc.ou.edu) with the mission of solving challenging radar research problems,
preparing students to become the next generation of scientists and engineers, and serving toempower economic growth and development in the field of weather radar. Currently, ARRC has 14
faculty members, four research scientists, eight engineers in radar software, hardware, andmechanicaldesignanddevelopment,
fiveadministrative
staffand
more
than
100
undergraduate and graduate students, postdocs,and visiting scholars from meteorology, hydrology,and engineering. ARRC is arguably one of thecountry’s largest academic research centers focusedon advancements in weather radar.
ARRC’s areas of emphasis exist in rapid hardware
prototyping, advanced signal processing, antennas,
hydrometeorology, clear-air sensing, UAS sensors, severe weather, applied electromagnetics, andmicrowave engineering, as highlighted in the left figure. ARRC operates a unique and extensive
set of instruments to investigate existing areas of study, and to explore new and importantresearch fields. Included in the ARRC facilities is a diverse set of radars of complementary
wavelengths, scanning options, and polarimetric capabilities including (1) S-band: Polarimetric
Phased Array Radar (PPAR) demonstrator (portable), (2) C-band: OU-PRIME (ground-base, dualpol, 1MW magnetron transmitter, and 0.5o beam width), SMART Radars (one single-pol and one
dual-pol mobile radars), (3) X-band: PX-1000 (compact, portable, dual-pol, solid state, polarimetricradar), RaXPol (mobile, dual-pol, and rapid scan of 180o/sec), AIR (mobile imaging radar with ultrahigh temporal resolution) and (4) UHF Wind Profiler: 915 MHz Boundary Layer Radar (clear-airturbulence sensing).
Through the collaborative nature instilled in its members, the ARRC has proven effective atdeveloping synergy between science and engineering in the field of radar. In the National Weather
Center and in its extensive laboratory and radar facilities, meteorology and engineering faculty andstudents work side-by-side to learn from each other and to tackle challenging problems in remotesensing,
microwave
engineering,andapplied
electromagnetics. One of the two anechoic chambers in
the recently completed Radar Innovations Lab (RIL) is
shown on the right figure, which is dedicated to precise
antenna characterization and is available for bothresearchers and students. This interdisciplinary esprit decorps has already had a profound effect on both theundergraduate and graduate educational experiences inradar provided to OU students. ARRC also strives toestablish and strengthen partnerships with academic,
research, and operation institutions and private sectors
both nationally and internationally. For example, ARRC

and DPRI and RISH from Kyoto University have had formal partnership to “enhance mutualcooperation and exchange of experience and knowledge toward sustainable capacity-building andthe prevention and mitigation of weather-related disasters.”

Research Achievements and Challenges
The ARRC consists of a vibrant group of faculty and students from both engineering andmeteorology, focused on solving challenging radar problems and preparing the next generation ofstudents. The technology and science emerging from the ARRC is absolutely on the bleeding edgeof the field, much of which is targeted at solving challenging phased array weather radar problems– the key component of future severe weather sensing systems. Additionally, ARRC developed
and fielded several sophisticated mobile radar systems along with accompanying signal processing
algorithms. These innovative sensing systems with enhanced capability can not only help us better
understanding fundamentals of severe storms, but also provide early warning of these hazardous
weather events. These can therefore reduce the risk of these weather related disasters. Some
examples are provided in the following.
Atmospheric Imaging Radar (AIR)Fast updates of radar observations on the order of few seconds have been desirable. For example,
sequences of radar images, visual observations, and videos in tornadoes and sub-tornado-scalevortices confirm the need for observations with volumetric updates on the time scale of 1 – 10 s, inorder to capture their formation and evolution, and their relationship to their parent storm.
Additionally, the rapid advection and small scales of the rolls in hurricane boundary layer require
temporal sampling on time-scales of tens of seconds
or less to be able to understand their formation andevolution, particularly as they merge and interact with
low-level features that occur at different scales andacross surface roughness interfaces. In order toimprove the temporal resolution on spotlight operation,
the single-polarized X-band Atmospheric Imaging
Radar (AIR) was developed in the ARRC, as shownon the left figure. AIR operates in a ``floodlight'' mode,utilizing a 25o vertical fan beam on transmit and 36
receiving arrays capable of a 1o beam width using
digital beamforming (DBF). In other words, a Range
Height Indicator (RHI) of radar measurements can be formed simultaneously, similar to taking apicture with an electromagnetic camera. This configuration, combined with mechanical scanning inazimuth, allows the current AIR to collect 180 o by 20 o volumes in approximately 9 s. The AIR has
operated during each of the past three spring convective seasons in the Southern plains (20122014), and is scheduled to operate in the Spring of 2015. As of 2014, a total of 8 tornadoes andover 20 supercells have been scanned at ranges as close as 3 km. The 3D view of storms withultra-high update times offered by AIR demonstrates its ability to accurately determine verticalvortex structure without the concern of advection.
Polarimetric Phased Array Radar Technology
Based on a sound theoretical foundation built over many years of research, the ARRC incollaboration with the National Severe Storms Lab (NSSL) of National Oceanic and AtmosphericAdministration (NOAA) built a portable polarimetric phased array radar (PPAR) testbed, which cansupport both conventional planar arrays (enhanced with dual polarization capability) and cylindricalarrays. The ARRC has designed and built complete polarimetric transmit/receive (TR) modules
exploiting the latest advances in gallium nitride semiconductor technology. The project has also
developed a diversified waveform generation, transmission and acquisition solution scalable tolarge arrays. This small-scale demonstrator is a significant achievement; however, a full-scale,higher performance system is the ultimate goal. Consequently, a design study for the full system,
funded by OU with Lockheed Martin as a sub-contractor, was completed in early 2014. The fullsystem is expected to exploit latest technologies to perform multiple tasks such as observations ofweather and aircraft, including unmanned aerial systems for collision avoidance and target
identification.

PX-1000
The PX-1000 is a transportable polarimetric X-band radar that utilizes twosolid-state transmitters, and a parabolic reflector with 1.8° beam width.
The control, data processing and visualization of PX-1000 are handled bya sleek software termed “iRadar”, developed in the ARRC. Designed,fabricated, and operated by the ARRC, the PX-1000 dual-channel
independent transmit chain opens up possibilities of novel waveformdiversity for improving polarimetric radar quality. For example, a time
frequency multiplexing (MTF) waveform, which was designed to alleviate
the limitation of blind range inherited in pulse compression, was tested
and demonstrated using PX-1000. In addition to advanced signal
processing, development such as spectral analysis and adaptive clutter
filtering, real-time acquisition of time-series data also facilitates pulse
compression development. The PX-1000 is well suited for long-term field
campaigns. For example, PX-1000 was deployed in Oklahoma, New
Mexico, Colorado, etc in the US for the study of wind shears, tornadoes,
cloud electrification in lightning, and quantitative precipitation estimate inmountainous areas. In addition, PX-1000 was successfully deployed inSouth Korea near Gwangju for a field campaign of snow precipitation.
The added value of a compact X-band radar in mountainous areas is best
demonstrated by PX-1000 on the right panel. The area of interest is in theMineral County, Colorado depicted by yellow circle on the top panel. It isevident from the top panels that the adjacent S-band WSR-88Ds (KGJX)
cannot provide the information of surface precipitation due to severe
beam blockage, while the strategically located PX-1000 can offer
accurate and timely information of the precipitation, as shown on the bottom panel, which wasused by the local forecast office and emergence managers for the decision of issuing warning.
Research Challenges and Opportunities
It is recognized in the ARRC that the greatest technological challenges in future weather radar isthe seamless integration of polarimetry and phased array in a practical system. Based on thetechnological foundation built in the past few years, the ARRC is moving forward on the design,fabrication, test, and deployment of the most advanced weather radar in the world. The plannedpolarimetric phased array radar will have over 7,000 antenna elements per face, each with its own
digital transmission and reception circuitry. This “all-digital” design will be the first of its kind in theworld, and will allow for optimal use of both polarimetric and phased array technology, solving theprimary roadblock for the development of advanced weather radar. In addition, this radar will allow
for the first time virtually complete control over the way electromagnetic energy is transmitted into
the atmosphere. Within one year of the beginning of the project, it is planned to have a functioning
Line Replaceable Unit (LRU), which will be replicated to build the entire radar. Initially started as
an internally funded project, congressional authorization will be required in order to support thecompletion of this ambitious project. Early estimates for the cost of the entire system are near
$30M.