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Full-Text Articles in Engineering
Phased-Array Feed Instrumentation And Processing For Astronomical Detection, Interference Mitigation, And Transient Parameter Estimation, Richard Allen Black
Phased-Array Feed Instrumentation And Processing For Astronomical Detection, Interference Mitigation, And Transient Parameter Estimation, Richard Allen Black
Theses and Dissertations
Radio astronomy, the survey and study of naturally occurring astronomical radio signals, is a challenging field in terms of engineering requirements. The typical astronomical signal of interest is incredibly faint, resulting in very low signal-to-noise ratios (SNRs) on the order of -30 dB or lower. To detect such signals, one must have an uncommonly low and stable receiver noise temperature, high gain through large aperture reflectors, and state-of-the-art signal processing algorithms. One must also be able to mitigate the effects of interference, the presence of which, even if extremely weak, can completely mask the faint astronomical signals of interest. To …
Advancements In Radio Astronomical Array Processing: Digital Back End Development And Interferometric Array Interference Mitigation, Mitchell Costus Burnett
Advancements In Radio Astronomical Array Processing: Digital Back End Development And Interferometric Array Interference Mitigation, Mitchell Costus Burnett
Theses and Dissertations
The Brigham Young University (BYU) Radio Astronomy Systems group, in collaboration with the National Radio Astronomy Observatory (NRAO), the Center for Astrophysics at West Virginia University (WVU), and the Green Bank Observatory (GBO) have developed, and commissioned, a broadband real-time digital back end processing system for a 38-element phased array feed (PAF) with 150 MHz of instantaneous bandwidth. This system is capable of producing coarse and fine channel correlations, and implements a real-time beamformer that forms 7 simultaneous dual-polarized beams. This thesis outlines the hardware and software development for the digital back end and presents on-telescope commissioning results. This system …
High-Sensitivity Phased Arrays For Radio Astronomy And Satellite Communications, Junming Diao
High-Sensitivity Phased Arrays For Radio Astronomy And Satellite Communications, Junming Diao
Theses and Dissertations
Radio astronomy is used to study stars, galaxies, black holes and gas clouds radiation at radio frequencies. Detecting extremely weak signals from deep space radio sources requires high sensitive feed system associated with large dish antennas. The key figure of merit is survey speed, or the time required to map a region of the sky to a given source flux density. Survey speed is proportional to the frequency bandwidth, the field of view or observable region of the sky, and the squared sensitivity, where sensitivity is related to reflector aperture efficiency and system noise temperature. Compared to the traditional single …
Real-Time Beamformer Development And Analysis Of Weak Signal Detection With Interference Mitigation For Phased-Array Feed Radio Astronomy, James Michael Brady
Real-Time Beamformer Development And Analysis Of Weak Signal Detection With Interference Mitigation For Phased-Array Feed Radio Astronomy, James Michael Brady
Theses and Dissertations
In recent years, the Brigham Young University (BYU) Radio Astronomy Systems group has developed phased-array feeds and the data acquisition processing systems necessary to perform radio astronomy observations. This thesis describes the development and testing of a real-time digital beamforming system that reduces both the time required to process phased-array feed data and the disk space used to record this data compared to post-processing beamforming systems. A real-data experiment is also discussed in this thesis, which focuses on some of the data post-processing required for one of BYU's data acquisition systems.Radio-frequency interference mitigation techniques for phased-array feed radio astronomy have …
Digital Back End Development And Interference Mitigation Methods For Radio Telescopes With Phased-Array Feeds, Richard Allen Black
Digital Back End Development And Interference Mitigation Methods For Radio Telescopes With Phased-Array Feeds, Richard Allen Black
Theses and Dissertations
The Brigham Young University (BYU) Radio Astronomy group, in collaboration with Cornell University, the University of Massachusetts, and the National Radio Astronomy Observatory (NRAO), have in recent years developed and deployed PAF systems that demonstrated the advantages of PAFs for astronomy. However, these systems lacked the necessary bandwidth and acquisition times to be scientifically viable. This thesis outlines the development of a 20-MHz bandwidth system that can acquire for much longer periods of time and across much larger bandwidths than previous BYU systems. A report of the deployment of this system on the 305-meter reflector at the Arecibo Observatory in …
Improved Methods For Phased Array Feed Beamforming In Single Dish Radio Astronomy, Michael James Elmer
Improved Methods For Phased Array Feed Beamforming In Single Dish Radio Astronomy, Michael James Elmer
Theses and Dissertations
Among the research topics needing to be addressed to further the development of phased array feeds (PAFs) for radio astronomical use are challenges associated with calibration, beamforming, and imaging for single dish observations. This dissertation addresses these concerns by providing analysis and solutions that provide a clearer understanding of the effort required to implement PAFs for complex scientific research. It is shown that calibration data are relatively stable over a period of five days and may still be adequate after 70 days. A calibration update system is presented with the potential to refresh old calibrators. Direction-dependent variations have a much …
Design And Polarimetric Calibration Of Dual-Polarized Phased Array Feeds For Radio Astronomy, Taylor D. Webb
Design And Polarimetric Calibration Of Dual-Polarized Phased Array Feeds For Radio Astronomy, Taylor D. Webb
Theses and Dissertations
Research institutions around the globe are developing phased array feed (PAF) systems for wide-field L-band radio astronomical observations. PAFs offer faster survey speeds and larger fields of view than standard single-pixel feeds, which enable rapid sky surveys and significantly increased scientific capability. Because deep space astronomical signals are inherently weak, PAF systems must meet stringent noise and sensitivity requirements. Meeting these requirements requires detailed modeling of the phased array itself as well as the reflector it is mounted on. This thesis details a novel approach to dual-pol PAF design that models the array and reflector as a complete system in …
Development Of L-Band Down Converter Boards And Real-Time Digital Backend For Phased Array Feeds, Vikas Asthana
Development Of L-Band Down Converter Boards And Real-Time Digital Backend For Phased Array Feeds, Vikas Asthana
Theses and Dissertations
Recent developments in the field of phased array feeds for radio astronomical reflector antennas, have opened a new frontier for array signal processing for radio astronomy observations. The goal is to replace single horn feeds with a phased array feed, so as to enable astronomers to cover more sky area in less time. The development of digital backend signal processing systems has been a major area of concentration for the development of science-ready phased array feeds for radio astronomers. This thesis focuses on the development of analog down-converter receivers and an FPGA-based digital backend for real-time data processing and analysis …
Development Of An Experimental Phased-Array Feed System And Algorithms For Radio Astronomy, Jonathan Charles Landon
Development Of An Experimental Phased-Array Feed System And Algorithms For Radio Astronomy, Jonathan Charles Landon
Theses and Dissertations
Phased array feeds (PAFs) are a promising new technology for astronomical radio telescopes. While PAFs have been used in other fields, the demanding sensitivity and calibration requirements in astronomy present unique new challenges. This dissertation presents some of the first astronomical PAF results demonstrating the lowest noise temperature and highest sensitivity at the time (66 Kelvin and 3.3 m^2/K, respectively), obtained using a narrowband (425 kHz bandwidth) prototype array of 19 linear co-polarized L-band dipoles mounted at the focus of the Green Bank 20 Meter Telescope at the National Radio Astronomy Observatory (NRAO) in Green Bank, West Virginia. Results include …
Radio Frequency Interference Mitigation On The Very Small Array, Alan Joseph Stemmons
Radio Frequency Interference Mitigation On The Very Small Array, Alan Joseph Stemmons
Theses and Dissertations
Radio astronomical synthesis imaging arrays can create images with resolution much higher than can single dish telescopes. However, one of the biggest problems that imaging arrays face is radio frequency interference (RFI). This interference corrupts signals and prevents accurate image creation. Therefore, it is necessary to remove this interference. This thesis discusses the synthesis imaging procedure and array spatial filtering methods to remove interference, including Multiple Sidelobe Canceller (MSC), Subspace Projection (SP), and Cross-Subspace Projection (CSP). The CLEAN algorithm, an image restoration technique, is also discussed. Various improvements to the VSA are discussed, including upgrades to the hardware and software …
Nineteen-Element Phased-Array Feed Development And Analysis On Effects Of Focal Plane Offset And Beam Steering On Sensitivity, Jacob S. Waldron
Nineteen-Element Phased-Array Feed Development And Analysis On Effects Of Focal Plane Offset And Beam Steering On Sensitivity, Jacob S. Waldron
Theses and Dissertations
Presented herein is the design and construction process in the expansion of BYU's seven-element experimental platform to a nineteen-element platform for phased array feed experiments. The nineteen-element system was deployed at the National Radio Astronomy Observatory (NRAO) in Green Bank West Virginia for use on the Green Bank 20-Meter Telescope. Numerical simulations were performed to determine how sensitivity was affected by electronic beam steering and offset of the phased array feed (PAF) relative to the focal plane of the reflector. These simulated results were then compared to experimental data.
Characterization Of A Phased Array Feed Model, David A. Jones
Characterization Of A Phased Array Feed Model, David A. Jones
Theses and Dissertations
Creating accurate software based models of phased array feeds (PAFs) is one of many steps to successfully integrating PAFs with current and future radio telescopes, which is a goal of many groups around the globe. This thesis characterizes the latest models of a 19 element hexagonal PAF of dipoles used by the BYU radio astronomy research group and presents comparisons of these models with experimental data obtained using a prototype array. Experiments were performed at the NRAO site in Green Bank, West Virginia, and utilized the outdoor antenna test range and 20 meter radio telescope. Accurate modeling of the PAF …
High-Speed Data Acquisition And Fpga Detected Pulse Blanking System For Interference Mitigation In Radio Astronomy, Micah Alexander Lillrose
High-Speed Data Acquisition And Fpga Detected Pulse Blanking System For Interference Mitigation In Radio Astronomy, Micah Alexander Lillrose
Theses and Dissertations
Radio astronomy is the discipline dedicated to the study of celestial emissions in the radio band from a few MHz to 300 GHz. In recent years, spurious emissions from man-made devices that operate at these frequencies have made detection of astronomical signals difficult. These harmful RF transmissions are called radio frequency interference (RFI). One strategy to remove RFI is to apply spatial filtering using an array antenna. This thesis documents the development of a high-speed data acquisition system used to record data from 7- and 19-element phased array feeds. The system supports synchronous sampling over all channels and streams data …
A Prototype Platform For Array Feed Development, James Richard Nagel
A Prototype Platform For Array Feed Development, James Richard Nagel
Theses and Dissertations
Radio frequency interference (RFI) is a growing problem for radio astronomers. One potential solution utilizes spatial filtering by placing an array of electrically small antennas at the focal plane of a parabolic reflector. This thesis documents the design and characterization of a prototype array feed and RF receiver that were used to demonstrate the spatial filtering principle. The array consists of a 7-element hexagonal arrangement of thickened dipole antennas tuned to a center frequency of 1600 MHz. The receiver is a two-stage, low-noise frequency mixer that is tunable over the entire L-band. This thesis also documents a new receiver design …
Effects Of Mutual Coupling On Interference Mitigation With A Focal Plane Array, Michael A. Jensen, Karl F. Warnick
Effects Of Mutual Coupling On Interference Mitigation With A Focal Plane Array, Michael A. Jensen, Karl F. Warnick
Faculty Publications
A focal plane array feed of electrically small elements has been proposed as a means for achieving high sensitivity for radio astronomy applications in the presence of radio frequency interference (RFI). For a broadband system, mutual coupling effects become significant as the array element spacing becomes small relative to the electromagnetic wavelength. We present a theoretical framework for modeling the effects of mutual coupling and for determining the optimal multiport matching network between array elements and front-end transistor low-noise amplifiers for maximum signal-to-noise ratio (SNR). Numerical results are given for a model scenario including spillover and amplifier thermal noise and …
Beamforming Techniques And Interference Mitigation Using A Multiple Feed Array For Radio Astronomy, Chad K. Hansen
Beamforming Techniques And Interference Mitigation Using A Multiple Feed Array For Radio Astronomy, Chad K. Hansen
Theses and Dissertations
Radio frequency interference has become a large problem to radio astronomers. This thesis proposes the idea that radio frequency interference can be mitigated using a phased array feed in conjunction with a large reflector. A phased array feed would allow radio astronomers to observe fainter signals than is currently possible, while at the same time enabling rapid sky surveys. A phased array feed was designed and simulated, and sensitivity optimization was performed on the array feed. It was shown that higher sensitivity can be achieved using a 7-element phased array feed than with a conventional waveguide feed. Simulations were ran …
Real-Time Adaptive Cancellation Of Satellite Interference In Radio Astronomy, Andrew Joseph Poulsen
Real-Time Adaptive Cancellation Of Satellite Interference In Radio Astronomy, Andrew Joseph Poulsen
Theses and Dissertations
Radio astronomy is the science of observing the heavens at radio frequencies, from a few kHz to approximately 300 GHz. In recent years, radio astronomy has faced a growing interference problem as radio frequency (RF) bandwidth has become an increasingly scarce commodity. A programmable real-time DSP least-mean-square interference canceller was developed and demonstrated as a successful method of excising satellite down-link signals from both an experimental platform at BYU, and the Green Bank Telescope at the National Radio Astronomy Observatory in West Virginia. A performance analysis of this cancellation system in the radio astronomy radio frequency interference (RFI) mitigation regime …