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Low-cost X-band radars are an emerging technology that offer significant advantages over traditional systems for weather remote sensing applications. X-band radars provide enhanced angular resolution at a fraction of the aperture size compared to larger, lower frequency systems. Because of their low cost and small form factor, these radars can now be integrated into more research and commercial applications. This work presents research and development activities using a low-cost, X-band (9410 MHz) Phase-Tilt Radar. The phase-tilt design is a novel phased array architecture that allows for rapid electronic scanning in azimuth and mechanical tilting in elevation, as a compromise between cost and performance. This work focuses on field studies and experiments in three meteorological applications. The first stage of research focuses on the real-world application of phased array radars in forest fire monitoring and observation. From April to May 2013, a phase-tilt radar was deployed to South Australia and underwent a field campaign to make polarimetric observations of prescribed burns within and around the Adelaide Hills region. Measurements show the real-time evolution of the smoke plume dynamics at a spatial and temporal resolution that has never before been observed with an X-band radar. This dissertation will perform data analysis on results from this field campaign. Results are compared against existing work, theories, and approaches. In the second stage of research, field experiments are performed to assess the data quality of X-band phased array radars. Specifically, this research focuses on the measurement of and techniques to improve the variance of weather product estimators for dual-polarized systems. Variability in the radar products is a complicated relationship between the radar system specifications, scanning strategy, and the physics governing precipitation. Here, the variance of the radar product estimators is measured using standard radar scanning strategies employed in traditional mechanical antenna systems. Results are compared against adaptive scan strategies such as beam multiplexing and frequency diversity. This work investigates the improvement that complex scanning strategies offer in dual-polarized, X-band phased array radar systems. In the third stage of research, simulations and field experiments are conducted to investigate the performance benefits of adaptive scanning to optimize the data quality of radar returns. This research focuses on the development and implementation of a waveform agile and adaptive scanning strategy to improve the quality of weather product estimators. Active phased array radars allow radar systems to quickly vary both scan pointing angles and waveform parameters in response to real-time observations of the atmosphere. As an evolution of the previous research effort, this work develops techniques to adaptively change the scan pointing angles, transmit and matched filter waveform parameters to achieve a desired level of data quality. Strategies and techniques are developed to minimize the error between observed and desired data quality measures. Simulation and field experiments are performed to assess the quality of the developed strategies.
Phase array antennas are a promising technology for weather surveillance radars. Their fast beam steering capability offer the potential of improving weather observations and extending warning lead times. However, one major problem associated with this technology is their high acquisition cost to be use in networked radar systems. One promising technology that could have a significant impact in the deployment of future dense networks of short-range X-band weather radars is the ``Phase-Tilt Radar'', a system that uses a one-dimensional phase scanned antenna array mounted over a tilting mechanism. This dissertation addresses some of specific challenges that arise in designing and implementing air-cooled, low-cost, one-dimensional phased antenna arrays for phase-tilt radars. The goal of this work is to develop methods that can lead to reduce the cost and enhance the performance of this type of systems. Specifically, the thesis focuses on three concrete areas. The first one is on the development of a versatile low-cost beam steering system that can enable dual-polarimetric phased array radars to operate with high-frequency repetition pulses, difference pulsing schemes, and modern scanning strategies. In particular, the dissertation will present the development of critical components and describes the concept of operations of the beam steering system. The second area is to develop a calibration technique for small phased arrays. The work focused in finding the calibration settings for the array that best fit to the desired excitation. The technique provides lower random errors than conventional approaches, enabling the implementation of radiation patterns with sidelobes closer to the desired level. Additionally, the technique is extended to solve the gain-drift problem occurring in the two-way antenna pattern due to the temperature changes. The third area studies the use of mutual coupling as signal injection technique to maintain the calibration of both array and radar. Future air-cooled phased array radars will require the use internal circuitry to calibrate the aspect of the radar that tends to change over time. In particular, this work is focused on developing low-cost calibration techniques to correct the antenna gain and radar constant from effects of temperature changes and element failures.
The Multifunction Phased Array Radar (MPAR) is one potentially cost-effective solution to meet the surveillance needs and of several agencies currently using decades-old radar networks. These agencies including the National Oceanic and Atmospheric Administration s (NOAA) National Weather Service (NWS), the Federal Aviation Administration (FAA), the Department of Defense (DOD) and the Department of Homeland Security (DHS) have many and varied requirements and possible applications of modern radar technology. This book analyzes what is lacking in the current system, the relevant capabilities of phased array technology, technical challenges, cost issues, and compares possible alternatives. Both specific and overarching recommendations are outlined.
Weather radar is a vital instrument for observing the atmosphere to help provide weather forecasts and issue weather warnings to the public. The current Next Generation Weather Radar (NEXRAD) system provides Doppler radar coverage to most regions of the United States (NRC, 1995). This network was designed in the mid 1980s and deployed in the 1990s as part of the National Weather Service (NWS) modernization (NRC, 1999). Since the initial design phase of the NEXRAD program, considerable advances have been made in radar technologies and in the use of weather radar for monitoring and prediction. The development of new technologies provides the motivation for appraising the status of the current weather radar system and identifying the most promising approaches for the development of its eventual replacement. The charge to the committee was to determine the state of knowledge regarding ground-based weather surveillance radar technology and identify the most promising approaches for the design of the replacement for the present Doppler Weather Radar. This report presents a first look at potential approaches for future upgrades to or replacements of the current weather radar system. The need, and schedule, for replacing the current system has not been established, but the committee used the briefings and deliberations to assess how the current system satisfies the current and emerging needs of the operational and research communities and identified potential system upgrades for providing improved weather forecasts and warnings. The time scale for any total replacement of the system (20- to 30-year time horizon) precluded detailed investigation of the designs and cost structures associated with any new weather radar system. The committee instead noted technologies that could provide improvements over the capabilities of the evolving NEXRAD system and recommends more detailed investigation and evaluation of several of these technologies. In the course of its deliberations, the committee developed a sense that the processes by which the eventual replacement radar system is developed and deployed could be as significant as the specific technologies adopted. Consequently, some of the committee's recommendations deal with such procedural issues.
This dissertation details the development and operation of a novel dual-polarized Phase-Tilt Weather Radar (PTWR) designed for meteorological applications. The use of radar has a well-documented history in detection and classification of weather phenomena, but due to the limited mechanical scanning speed, its usage for severe weather observations remains far from ideal. The PTWR utilizes phased-array technology and provides unique capabilities such as smart scanning, fast scan update, and tracking. This technology is considered a candidate for a replacement and consolidation of the current US weather and surveillance radar networks. The dissertation can be divided into three parts. First, the hardware design of the radar is presented. Methods of an element and array calibration are discussed. The measured sidelobe level and pattern match exhibit satisfactory performance. The algorithms for signal processing in alternate transmit alternate receive mode of operation are described in detail. The PTWR weather detection capability is validated by an inter-comparison with a collocated X-band high-power radar. These tests showed correlation exceeding 90% for measurements of reflectivity in a convective storm system. The results support the hypothesis that phased-array technology poses an attractive solution for weather remote sensing. The second part addresses the radar waveform considerations. The sensitivity of the radar can be improved by several decibels by means of pulse compression techniques. This is necessary, since the PTWR utilizes low-power solid-state transmitters. The work discusses the trade-offs in waveform design and introduces a novel compression filter, which outperforms traditional window-based solutions. The pulse compression performance is validated using clutter data collected by the PTWR, proving that a deep sidelobe reduction in excess of 40dB can be achieved at the minimal penalty in signal-to-noise level (below 0.5dB). Finally, the third part focuses on the scanning geometry of a 1-D phase-tilt ar- chitecture. It is shown that as the elevation angle is increased, the measurements are affected by a self-induced apparent canting angle. The methods of polarization rotation correction are presented. The biases in typical weather radar products such as reflectivity, differential reflectivity, correlation coefficient, and specific propagation phase, are investigated. The analysis shows that for elevation angles below 15deg , the retrievals errors are acceptable.
The Electronically Steered Phased Array is one of the most versatile antennas used in radars applications. Some of the advantages of electronic steering are faster scan, no moving parts and higher reliability. However, the cost of phased arrays has always been prohibitive - in the order of $1M per square meter. The cost of a phased array is largely impacted by the cost of the high frequency electronics at each element and the cost of packaging. Advances in IC integration will allow incorporating multiple elements such as low noise amplifier, power amplifier, phase shifters and up/down-conversion into one or two ICs. Even though the cost for large quantities of ICs (both Silicon and GaAs) has lowered, the high cost of IC packaging and the array backplane still make the use of phase arrays for radar applications costly. The focus of this research is on techniques that reduce the packaging and the backplane cost of large electronically steered arrays. These techniques are based on simplified signal distributions schemes, reduction of layers in the backplane and use of inexpensive materials. Two architectures designed based on these techniques, as well as a novel BGA active antenna package for dual polarized phased arrays are presented. The first architecture, called the series fed row-column architecture, focuses on the reduction of phase shifters and control signals used in the backplane of the array. The second architecture, called the parallel plate feed architecture, is based on a simplified scheme for distribution of the local oscillator signal. A prototype making use of each one of these architectures is presented. Analysis of advantages and disadvantages of each of these architectures is described. The necessity of cost reduction is a factor that can possibly impact the polarization performance of the antenna. This factor is a motivation to study and develop calibration techniques that reduce the cross-polarization of electronically steered phased arrays. Advances on Interleaving Sparse Arrays, a beam forming technique for polarization improvement/correction in phased arrays, are also presented.
This book reviews the principles of Doppler radar and emphasizes the quantitative measurement of meteorological parameters. It illustrates the relation of Doppler radar data and images to atmospherix phenomena such as tornados, microbursts, waves, turbulence, density currents, hurricanes, and lightning. Radar images and photographs of these weather phenomena are included. Polarimetric measurements and data processing An updated section on RASS Wind profilers Observations with the WSR-88D An updated treatment of lightning Turbulence in the planetary boundary layer A short history of radar Chapter problem sets
This 2001 book provides a detailed introduction to the principles of Doppler and polarimetric radar, focusing in particular on their use in the analysis of weather systems. The design features and operation of practical radar systems are highlighted throughout the book in order to illustrate important theoretical foundations. The authors begin by discussing background topics such as electromagnetic scattering, polarization, and wave propagation. They then deal in detail with the engineering aspects of pulsed Doppler polarimetric radar, including the relevant signal theory, spectral estimation techniques, and noise considerations. They close by examining a range of key applications in meteorology and remote sensing. The book will be of great use to graduate students of electrical engineering and atmospheric science as well as to practitioners involved in the applications of polarimetric radar systems.
This edition is the most comprehensive and informative available on radar systems and technology. Thoroughly revised and updated to reflect the advances made in radar over the past two decades. Charts/graphs.
With their images practically ubiquitious in the daily media, weather radar systems provide data not only for understanding weather systems and improving forecasts (especially critical for severe weather), but also for hydrological applications, flood warnings and climate research in which ground verification is needed for global precipitation measurements by satellites. This book offers an accessible overview of advanced methods, applications and modern research from the European perspective. An extensive introductory chapter summarizes the principles of weather radars and discusses the potential of modern radar systems, including Doppler and polarisation techniques, data processing, and error-correction methods. Addressing both specialist researchers and nonspecialists from related areas, this book will also be useful for graduate students planning to specialize in this field