29-05-2012, 04:39 PM
DESIGN OF AN FPGA-BASED ARRAY FORMATTER
FOR CASA PHASE-TILT RADAR SYSTEM
[attachment=23398]
ABSTRACT
Weather monitoring and forecasting systems have witnessed rapid advancement
in recent years. However, one of the main challenges faced by these systems is poor
coverage in lower atmospheric regions due to earth's curvature. The Engineering
Research Center for the Collaborative Adaptive Sensing of the Atmosphere (CASA)
has developed a dense network of small low-power radars to improve the coverage of
weather sensing systems. Traditional, mechanically-scanned antennas used in these
radars are now being replaced with high-performance electronically-scanned phased-
arrays. Phased-Array radars, however, require large number of active microwave
components to scan electronically in both the azimuth and elevation planes, thus sig-
ni cantly increasing the cost of the entire radar system. To address this issue, CASA
has designed a \Phase-Tilt" radar, that scans electronically in azimuth and mechan-
ically in elevation. One of the core components of this system is the Phased-Array
controller or the Array Formatter.
INTRODUCTION
State-of-the-art weather prediction systems rely on the use of advanced radar
systems for ecient and accurate information. Radar systems study the quantity of
interest by transmitting an electromagnetic signal in space and detecting the echoed
signal received from the target [17]. The comparison of transmit and receive signals
reveals crucial target information, such as location, size, etc. The process is repeated
several times to increase the accuracy of the target information collected. Current
radar systems are digitally controlled using modern computers and sophisticated data
acquisition systems. A modern radar system typically consists of a computer, an
antenna panel for transmitting and receiving signals, and a data acquisition system
for processing digital and analog signals as shown in Figure 1.1. The Data Acquisition
Systems consists of Analog to Digital Converters, analog and digital circuitry, and
hardware support to perform complex signal processing algorithms. They also require
several high-speed interfaces to communicate with di erent radar components.
Dual-Polarized Radars
Dual-polarized radars have the ability to transmit or receive signals in either
polarization. The variable transmit and receive electric eld polarizations in the
signals allows dual-polarized radars to measure hydrometeor characteristics, such as
shape, size, and di erentiate thermodynamic phase [6]. This helps in determining
rainfall rates, and sometimes discriminate between between liquid or ice phases of the
hydrometeor [6]. A weather radar usually transmits in one polarization and receives
in the other or same polarization depending on the scattering characteristics of the
target.
Phase-Tilt Antenna Scanning Sub-system
The Phase-Tilt antenna scanning sub-system consists of 64 T/R Modules, antenna
elements, and a Mechanical Actuator or Tilt Controller as shown in Figure 2.2. A
picture of the passive antenna array is shown in Figure 2.5. The antenna scanning
sub-system consists of four Line Replaceable Units (LRUs).
FOR CASA PHASE-TILT RADAR SYSTEM
[attachment=23398]
ABSTRACT
Weather monitoring and forecasting systems have witnessed rapid advancement
in recent years. However, one of the main challenges faced by these systems is poor
coverage in lower atmospheric regions due to earth's curvature. The Engineering
Research Center for the Collaborative Adaptive Sensing of the Atmosphere (CASA)
has developed a dense network of small low-power radars to improve the coverage of
weather sensing systems. Traditional, mechanically-scanned antennas used in these
radars are now being replaced with high-performance electronically-scanned phased-
arrays. Phased-Array radars, however, require large number of active microwave
components to scan electronically in both the azimuth and elevation planes, thus sig-
ni cantly increasing the cost of the entire radar system. To address this issue, CASA
has designed a \Phase-Tilt" radar, that scans electronically in azimuth and mechan-
ically in elevation. One of the core components of this system is the Phased-Array
controller or the Array Formatter.
INTRODUCTION
State-of-the-art weather prediction systems rely on the use of advanced radar
systems for ecient and accurate information. Radar systems study the quantity of
interest by transmitting an electromagnetic signal in space and detecting the echoed
signal received from the target [17]. The comparison of transmit and receive signals
reveals crucial target information, such as location, size, etc. The process is repeated
several times to increase the accuracy of the target information collected. Current
radar systems are digitally controlled using modern computers and sophisticated data
acquisition systems. A modern radar system typically consists of a computer, an
antenna panel for transmitting and receiving signals, and a data acquisition system
for processing digital and analog signals as shown in Figure 1.1. The Data Acquisition
Systems consists of Analog to Digital Converters, analog and digital circuitry, and
hardware support to perform complex signal processing algorithms. They also require
several high-speed interfaces to communicate with di erent radar components.
Dual-Polarized Radars
Dual-polarized radars have the ability to transmit or receive signals in either
polarization. The variable transmit and receive electric eld polarizations in the
signals allows dual-polarized radars to measure hydrometeor characteristics, such as
shape, size, and di erentiate thermodynamic phase [6]. This helps in determining
rainfall rates, and sometimes discriminate between between liquid or ice phases of the
hydrometeor [6]. A weather radar usually transmits in one polarization and receives
in the other or same polarization depending on the scattering characteristics of the
target.
Phase-Tilt Antenna Scanning Sub-system
The Phase-Tilt antenna scanning sub-system consists of 64 T/R Modules, antenna
elements, and a Mechanical Actuator or Tilt Controller as shown in Figure 2.2. A
picture of the passive antenna array is shown in Figure 2.5. The antenna scanning
sub-system consists of four Line Replaceable Units (LRUs).