Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 9 of 9
Full-Text Articles in Engineering
Phased Array Digital Beamforming Algorithms And Applications, David Moyle Marsh
Phased Array Digital Beamforming Algorithms And Applications, David Moyle Marsh
Theses and Dissertations
With the expansion of unmanned aircraft system (UAS) technologies, there is a growing need for UAS Traffic Management (UTM) systems to promote safe operation and development. To be successful, these UTM systems must be able to detect and track multiple drones in the presence of clutter. This paper examines the implementation of different algorithms on a compact, X-band, frequency modulated continuous wave (FMCW) radar in an effort to enable more accurate detection and estimation of drones. Several algorithms were tested through post processing on actual radar data to determine their accuracy and usefulness for this system. A promising result was …
Real-Time Beamforming Algorithms For The Focal L-Band Array On The Green Bank Telescope, Mark William Ruzindana
Real-Time Beamforming Algorithms For The Focal L-Band Array On The Green Bank Telescope, Mark William Ruzindana
Theses and Dissertations
A phased array feed (PAF) provides a contiguous, electronically synthesized wide field of view for large-dish astronomical observatories. Significant progress has been made in recent years in improving the sensitivity of PAF receivers though optimizing the design of the antenna array, cryogenic cooling of the front end, and implementation of real-time correlation and beamforming in digital signal processing. FLAG is a 19 dual-polarized element phased array with cryogenic LNAs, direct digitization of RF signals at the front end, digital signal transport over fiber, and a real time signal processing back end with up to 150 MHz bandwidth. The digital back …
Passive And Electronically Steered Array Planar Feeds For Satellite Communications, Kyle C. Browning
Passive And Electronically Steered Array Planar Feeds For Satellite Communications, Kyle C. Browning
Theses and Dissertations
As the need for more bandwidth increases, satellite communication (SatCom) terminals are forced to climb higher in frequency. Higher frequency means greater propagation losses, and so antenna gain and sensitivity have to increase. The higher the gain, the more difficult it is to point the antenna. To make matters even more challenging, consumers are requesting satellite links in harsher environments and on moving vehicle and planes. In order to meet today's challenges and improve on dish feeds, research is ongoing to replace fixed-beam feedhorns with smaller, cheaper, and lighter PCB based antennas and to develop low-cost electronically steered array feeds …
Improved Channel Probing For Secret Key Generation With Multiple Antenna Systems, Britton T. Quist
Improved Channel Probing For Secret Key Generation With Multiple Antenna Systems, Britton T. Quist
Theses and Dissertations
Establishing secret keys from the commonly-observed randomness of reciprocal wireless propagation channels has recently received considerable attention. In this work we propose improved strategies for channel estimation between MIMO or beamforming systems for secret key generation. The amount of mutual information that can be extracted from the channel matrix estimates is determined by the quality of channel matrix estimates. By allocating increased energy to channel estimation for higher gain beamforming combinations at the expense of low-gain combinations, key establishment performance can be increased. Formalizing the notion of preferential energy allocation to the most efficient excitations is the central theme of …
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 …
Active Impedance Matching And Sensitivity Optimized Phased Array Feed Design For Radio Astronomy, David E. Carter
Active Impedance Matching And Sensitivity Optimized Phased Array Feed Design For Radio Astronomy, David E. Carter
Theses and Dissertations
One of the many challenges in radio astronomy is the ability to make accurate measurements quickly. In recent years engineers and astronomers have begun implementing phased array feeds (PAFs) as a way to negate the long observation times required by single antenna feeds. Unfortunately, large mutual coupling and other loss terms result in low sensitivity, restricting PAF usefulness in on dish observation. This thesis addresses several ways to reduce mutual coupling and maximize sensitivity for PAFs in radio astronomy. Antenna design of this magnitude requires accurate modeling capabilities. To this end, electromagnetic software models and low loss component designs are …
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 …
Transmission Strategies For Wireless Multi-User, Multiple-Input, Multiple-Output Communication Channels, Quentin H. Spencer
Transmission Strategies For Wireless Multi-User, Multiple-Input, Multiple-Output Communication Channels, Quentin H. Spencer
Theses and Dissertations
Multiple-Input, Multiple-Output (MIMO) processing techniques for wireless communication are of interest for next-generation systems because of their potential to dramatically improve capacity in some propagation environments. When used in applications such as wireless LAN and cellular telephony, the MIMO processing methods must be adapted for the situation where a base station is communicating with many users simultaneously. This dissertation focuses on the downlink of such a channel, where the base station and all of the users have antenna arrays. If the transmitter has advance knowledge of the users' channel transfer functions, it can use that information to minimize the interuser …