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Optical phased array feasibility study, STL-029-21, Year 1 of 1
Presentation to be presented during the Site-Directed Research and Development (SDRD) program FY 2021 review meeting (Webex), September 22–23, 2021.
Science Applications of Phased Array Radars
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A Primer on Phased Array Radar Technology for the Atmospheric Sciences
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Three-dimensional broadband nonlinear phased array imaging
System include an ultrasonic transducer configured to couple to a nondestructive testing (NDT) sample and configured to produce and direct an ultrasonic probe wave at a selected frequency into a subsurface region of the NDT sample, a 3D laser scanning vibrometer configured to direct a detection beam in a scan area on a surface of the NDT sample and to receive a return beam from the scan area, and to detect, based on the return beam, a 3D motion of the surface across a wideband frequency range, and a processor, and a memory configured with instructions that, when executed by the processor, cause the processor to produce sub-surface image data of the NDT sample at multiple harmonics of the selected frequency in the wideband frequency range based on the detected 3D surface motion, wherein the sub-surface image data describes a nonlinear defect response produced in the NDT sample by interaction of the ultrasonic probe wave with the subsurface region.
Final Report: Guided Wave Phased Array for Spent Fuel Dry Storage Canister Evaluation
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Highly Variable Cycle Nozzle Concept: Validation of Flow and Noise Predictions
Results from experimental and numerical studies of highly Variable Cycle (HVC) exhaust model were presented. The model was designed and fabricated under a Supersonics NRA awarded to Rolls-Royce. The model had a lobed mixer for the core stream nozzle, and elliptic fan stream nozzle, and an ejector. Experiments included far-field acoustic array, phased array, and Particle Image Velocimetry (PIV) measurements. Numerical studies included flow simulations using the WIND-US code and far-field acoustic solutions using an acoustic analogy developed by Goldstein (2003) and Leib and Goldstein (2011). Far-field acoustic measurements showed increased noise levels over the round baseline nozzle when using non-static forward flight conditions. Phased array measurements showed noise sources near the ejector doors when tones were produced for small ejector door positions. Ejector door separation identified in the experiments was reproduced in the numerical flow simulations. Acoustic solutions were unable to match levels measured in the peak jet noise direction indicating additional development work is needed to predict noise from highly three-dimensional flows.
Phased Antenna Array for Global Navigation Satellite System Signals
Systems and methods for phased array antennas are described. Supports for phased array antennas can be constructed by 3D printing. The array elements and combiner network can be constructed by conducting wire. Different parameters of the antenna, like the gain and directivity, can be controlled by selection of the appropriate design, and by electrical steering. Phased array antennas may be used for radio occultation measurements.
Phased array-fed antenna configuration study
The scope of this contract entails a configuration study for a phased array fed transmit antenna operating in the frequency band of 17.7 to 20.2 GHz. This initial contract provides a basis for understanding the design limitations and advantages of advanced phased array and cluster feeds (both utilizing intergral MMIC modules) illuminating folded reflector optics (both near field and focused types). Design parametric analyses are performed utilizing as constraints the objective secondary performance requirements of the Advanced Communications Technology Satellite (Table 1.0). The output of the study provides design information which serves as a data base for future active phased array fed antenna studies such as detailed designs required to support the development of a ground tested breadboard. In general, this study is significant because it provides the antenna community with an understanding of the basic principles which govern near field phased scanned feed effects on secondary reflector system performance. Although several articles have been written on analysis procedures and results for these systems, the authors of this report have observed phenomenon of near field antenna systems not previously documented. Because the physical justification for the exhibited performance is provided herein, the findings of this study add a new dimension to the available knowledge of the subject matter.
Phased-Antenna-Array Conical Scanning
Antenna pointing faster than mechanical scanning. Three antenna phased array connected to receiving signal-processing system through two phase-shifting networks. Two networks simultaneously steer phased array in two slightly-different beam directions; one for scanning, one for tracking. Technique has many uses in military and civilian radar, principally in tracking aircraft, balloonborne weather instruments, and other moving signal sources or reflectors.
Adaptive array technique for differential-phase reflectometry in QUEST
A Phased Array Antenna (PAA) was considered as launching and receiving antennae in reflectometry to attain good directivity in its applied microwave range. A well-focused beam was obtained in a launching antenna application, and differential-phase evolution was properly measured by using a metal reflector plate in the proof-of-principle experiment at low power test facilities. Differential-phase evolution was also evaluated by using the PAA in the Q-shu University Experiment with Steady State Spherical Tokamak (QUEST). A beam-forming technique was applied in receiving phased-array antenna measurements. In the QUEST device that should be considered as a large oversized cavity, standing wave effect was significantly observed with perturbed phase evolution. A new approach using derivative of measured field on propagating wavenumber was proposed to eliminate the standing wave effect.
Development of In-Flow Phased Microphone Array Windscreen Corrections for Small and Large Arrays
The corrections needed in acoustic level measurements using an in-flow phased-array were documented with detailed measurements in the NASA Ames 25- by 18- by 11-Ft Anechoic Chamber for 4 different in-flow arrays fitted with conformal windscreens of stainless-steel wire cloth and Kevlar120 fabric. This study considered the effects of source measurement angle and distance, and the effects of compact vs large distributed broadband calibration-sources. The study verified a simple geometric scaling that accurately derives the windscreen correction for arbitrary incidence angles from the correction measured at normal incidence. The acoustic corrections for windscreens of stainless-steel wire cloth with 200x600 wires/inch were significantly smaller and more regular than for the Kevlar120 windscreen. The qualitative effects of screen tautness were measured and found to be insignificant for the typical assembly specifications at Ames. Correcting phased array peak levels with the measured windscreen corrections created results that compare well with free-field microphone measurements of broadband noise sources.
Automated Array Assembly, Phase 2
The Automated Array Assembly Task, Phase 2 of the Low Cost Silicon Solar Array Project is a process development task. The contract provides for the fabrication of modules from large area tandem junction cells (TJC). During this quarter, effort was focused on the design of a large area, approximately 36 sq cm, TJC and process verification runs. The large area TJC design was optimized for minimum I squared R power losses. In the TJM activity, the cell-module interfaces were defined, module substrates were formed and heat treated and clad metal interconnect strips were fabricated.
An Agile Beam Transmit Array Using Coupled Oscillator Phase Control
A few years ago York and colleagues suggested that injection locking of voltage controlled oscillators could be used to implement beam steering in a phased array [I]. The scheme makes use of the fact that when an oscillator is injection locked to an external signal, the phase difference between the output of the oscillator and the injection signal is governed by the difference between the injection frequency and the free running frequency of the oscillator (the frequency to which the oscillator is tuned). Thus, if voltage controlled oscillators (VCOs) are used, this phase difference is controlled by an applied voltage. Now, if a set of such oscillators are coupled to nearest neighbors, they can be made to mutually injection lock and oscillate as an ensemble. If they are all tuned to the same frequency, they will all oscillate in phase. Thus, if the outputs are connected to radiating elements forming a linear array, the antenna will radiate normal to the line of elements. Scanning is accomplished by antisymmetrically detuning the end oscillators in the array by application of a pair of appropriate voltages to their tuning ports. This results in a linear phase progression across the array which is just the phasing required to scan the beam. The scan angle is determined by the degree of detuning. We have constructed a seven element one dimensional agile beam array at S-band based on the above principle. Although, a few such arrays have been built in the past, this array possesses two unique features. First, the VCO MMICs have buffer amplifiers which isolate the output from the tuning circuit, and second, the oscillators are weakly coupled to each other at their resonant circuits rather than their outputs. This results in a convenient isolation between the oscillator array design and the radiating aperture design. An important parameter in the design is the so called coupling phase which determines the phase shift of the signals passing from one oscillator to its neighbors. Using this array, we have been able to verify the theoretical predictions concerning the effect of this phase on both the locking range and ensemble frequency of the array. However, the scan range achieved fell somewhat short of the theoretical value because of the amplitude variation of the oscillator outputs with tuning.
Design for steering accuracy in antenna arrays using shared optical phase shifters
Uniform linear phased arrays where many radiating elements share a relatively small number of phase shifters are investigated. Such architectures arise in arrays which derive the time delays in the signal paths from a small group of independent phase shifters. In particular, a true time-delay device which has been suggested recently for optically controlled arrays is used as the basic phase shifter. Different architectures, viz. alternative procedures of deriving the necessary time delay for each antenna in the face of phase-shifter inaccuracies, are examined. The variance of the steered beam's direction is used as the performance criterion. The direction-optimal architecture is obtained by means of quadratic programming, and is shown not to be unique. The nonuniqueness of the optimal architecture is exploited to improve other characteristics of the array's beam shape, and the optimal solution is shown to compare favorably with a suboptimal interleaved solution which is easier to implement.
Phased array-based nonlinear wave mixing technique: Application to lack-of-fusion porosity characterization in additively manufactured metals
The objective of this research is to demonstrate the effectiveness of a phased array-based nonlinear wave mixing technique to characterize internal, localized microscale damage in an additively manufactured (AM) component. By using phased arrays for the generation of the incident waves, it is possible to produce a nonlinear wave mixing scanning technique without the need for immersion or changing coupling conditions. The phased arrays can be configured to generate incident waves in multiple directions that meet the resonance conditions required for nonlinear wave mixing at a variety of internal locations. This allows for the scanning of a specimen without the removal and re-coupling of the source transducers, leading to greater scanning speed and repeatability. To demonstrate the accuracy of this phased array wave mixing approach, measurements of acoustic nonlinearity in an AM component are first made with a bulk wave second harmonic generation through thickness measurement. Next, nonlinear wave mixing measurements are made with single element transducers to confirm the sensitivity of the proposed nonlinear wave mixing approach to lack-of-fusion porosity in AM metals. Finally, phased arrays are used to highlight the effectiveness of the proposed nonlinear wave mixing technique in these same AM components.
Automated Array Assembly, Phase 2. Low-cost Solar Array Project, Task 4
Work was done to verify the technological readiness of a select process sequence with respect to satisfying the Low Cost Solar Array Project objectives of meeting the designated goals of $.50 per peak watt in 1986 (1975 dollars). The sequence examined consisted of: (1) 3 inches diameter as-sawn Czochralski grown 1:0:0 silicon, (2) texture etching, (3) ion implanting, (4) laser annealing, (5) screen printing of ohmic contacts and (6) sprayed anti-reflective coatings. High volume production projections were made on the selected process sequence. Automated processing and movement of hardware at high rates were conceptualized to satisfy the PROJECT's 500 MW/yr capability. A production plan was formulated with flow diagrams integrating the various processes in the cell fabrication sequence.