Corrections for Mirror Sources in Phased Array Processing Techniques

Abstract Since 2007 the advancement of the National Weather Radar Testbed Phased-Array Radar (NWRT PAR) hardware and software capabilities has been supporting the implementation of high-temporal-resolution (∼1 min) sampling. To achieve the increase in computational power and data archiving needs required for high-temporal-resolution sampling, the signal processor was upgraded to a scalable, Linux-based cluster with a distributed computing architecture. The development of electronic adaptive scanning, which can reduce update times by focusing data collection on significant weather, became possible through functionality added to the radar control interface and real-time controller. Signal processing techniques were implemented to address data quality issues, such as artifact removal and range-and-velocity ambiguity mitigation, absent from the NWRT PAR at its installation. The hardware and software advancements described above have made possible the development of conventional and electronic scanning capabilities that achieve high-temporal-resolution sampling. Those scanning capabilities are sector- and elevation-prioritized scanning, beam multiplexing, and electronic adaptive scanning. Each of these capabilities and related sampling trade-offs are explained and demonstrated through short case studies.

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Finding the boom: Phased array processing applied to sonic boom direction of arrival estimation

International Journal of Aeroacoustics ◽

10.1177/1475472x17718737 ◽

2017 ◽

Vol 16 (4-5) ◽

pp. 230-254

Author(s):

Todd Schultz ◽

James R Underbrink ◽

LC Hunting ◽

James Giannakis ◽

Matthew D Moore ◽

...

Keyword(s):

Wave Front ◽

Phased Array ◽

Array Processing ◽

Time Estimation ◽

Direction Of Arrival ◽

Test Point ◽

Propagation Path ◽

Sonic Boom ◽

Circular Aperture ◽

Aperture Diameter

From 29 October 2012 to 7 November 2012, 73 supersonic passes of an F-18 aircraft were observed over a dry lake bed at Edwards Air Force Base as part of NASA’s Farfield Investigation of No-boom Thresholds project, which was conceived to measure the characteristics of sonic booms at the boundaries of their decay, where overpressure is exceptionally low, thereby stretching the limits of current prediction methods. Each pass was recorded by a 55-microphone phased array sensor system with a circular aperture diameter of 2000 ft (609.6 m). The data were processed using a novel time domain array processing algorithm to estimate the direction of arrival and trace speed of the sonic boom wave front along the plane of the phased array. The results from the phased array processing are consistent with the known location of the test aircraft for each processed flight and are consistent with expectations for direction of arrival due to atmospheric refraction. Near real-time estimation of the sonic boom direction of arrival, trace speed along the ground, and visualization of the propagation of the sonic boom wave front are possible. This could allow the test team to assess the data and determine if the target of the test point has been met while the test aircraft is still in flight. This would enable improved test efficiency and efficacy, ultimately improving the value of the test campaign. The measured direction of arrival also provides sonic boom propagation numerical prediction code validation. Most sonic boom prediction codes provide the propagation path of the sonic boom and thus the direction of arrival of the sonic boom at a point on the ground. Thus for predictions made using the actual flight data measured at the time of the test, the predicted direction of arrival and measured direction of arrival can be directly compared to help validate the prediction codes.

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