Search NASA⌕ Search

SEARCH · Search NASA

Results for “PHASE LOCK”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
NASA NTRS1999

Stable CW Single Frequency Operation of Fabry-Perot Laser Diodes by Self-Injection Phase Locking

Previously, single-frequency semiconductor laser operation using fiber Bragg gratings has been achieved by tWo methods: 1) use of the FBG as the output coupler for an anti-reflection-coated semiconductor gain element'; 2) pulsed operation of a gain-switched Fabry-Perot laser diode with FBG-optical and RF-electrical feedback'. Here, we demonstrate CW single frequency operation from a non-AR coated Fabry-Perot laser diode using only FBG optical feedback.

Duerksen, Gary L.↗
NASA NTRS2006

Interrupt-based Phase-locked Frequency Multiplier

A method aud system utilize a processor's digital timer and two interrupts to form a frequency multiplier. The first internipt's processing time window is definable by a first uumber of counts C(sub 1), of the digital timer while the second interrupt's processing time window is definable by a second number of counts C(sub 2) of the digital timer. A count value CV utilized by the systedmethod is based on a desired frequency multiplier N(sub 1), the timer clock rate, and the tiole required for one cycle of an input signal. The first interrupt is triggered upon completion of one cycle ofthe input sigual at which point the processing time window associated therewith begins. The second interrupt is triggered each time the timer's overflow signal is generated at which point the processing time window associated with the second interrupt begins. During the occurrence of the second interrupt's processing. the count value CV is modified to maintain the first interrupt's processing time window approximately centered between two of the second internipt's processing time windows.

Palumbo, Daniel L.↗
NASA NTRS2005

Frequency and Phase-lock Control of a 3 THz Quantum Cascade Laser

We have locked the frequency of a 3 THz quantum cascade laser (QCL) to that of a far-infrared gas laser with a tunable microwave offset frequency. The locked QCL line shape is essentially Gaussian, with linewidths of 65 and 141 kHz at the -3 and -10 dB levels, respectively. The lock condition can be maintained indefinitely, without requiring temperature or bias current regulation of the QCL other than that provided by the lock error signal. The result demonstrates that a terahertz QCL can be frequency controlled with l-part-in-lO(exp 8) accuracy, which is a factor of 100 better than that needed for a local oscillator in a heterodyne receiver for atmospheric and astronomic spectroscopy.

Betz, A. L.↗
NASA NTRS1994

Hydrogen-Maser/Ruby-Maser/Quartz-Crystal Oscillator

Highly stable oscillator suitable for use as 100-MHz frequency standard consists of 100-MHz hydrogen maser combined with double-phase-locked-loop receiver. Generates 100-MHz signal with reduced noise. Contains 100-MHz voltage-controlled quartz-crystal oscillator (VCO) locked in phase to superconducting-cavity maser oscillator (SCMO). SCMO, locks in phase to hydrogen maser, phase-locking receiver and its SCMO/ VCO combination to hydrogen maser. Aspects of SCMO described in previous reports, including "Performance of Superconducting-Cavity Maser" (NPO-18175), NASA Tech Briefs, Vol. 15, No. 6. Performances of component oscillators complement each other.

Wang, Rabi T.↗
DOE OSTI2024

Shapiro steps and stability of skyrmions interacting with alternating anisotropy under the influence of ac and dc drives

Here we use atomistic simulations to examine the sliding dynamics of a skyrmion in a two-dimensional system containing a periodic one-dimensional stripe pattern of variations between low and high values of the perpendicular magnetic anisotropy. The skyrmion changes in size as it crosses the interface between two anisotropy regions. On applying combined dc and ac driving in either parallel or perpendicular directions, we observe a wide variety of Shapiro steps, Shapiro spikes, and phase-locking phenomena. The phase-locked orbits have two-dimensional dynamics due to the gyrotropic or Magnus dynamics of the skyrmions and are distinct from the phase-locked orbits found for strictly overdamped systems. Along a given Shapiro step when the ac drive is perpendicular to the dc drive, the velocity parallel to the ac drive is locked while the velocity in the perpendicular direction increases with increasing drive to form Shapiro spikes. At the transition between adjacent Shapiro steps, the parallel velocity jumps up to the next step value, and the perpendicular velocity drops. The skyrmion Hall angle shows a series of spikes as a function of increasing dc drive, where the jumps correspond to the transition between different phase-locked steps. At high drives, the Shapiro steps and Shapiro spikes are lost. When both the ac and dc drives are parallel to the stripe periodicity direction, Shapiro steps appear, while if the dc drive is parallel to the stripe periodicity direction and the ac drive is perpendicular to the stripe periodicity, then there are only two locked phases, and the skyrmion motion consists of a combination of sliding along the interfaces between the two anisotropy values and jumping across the interfaces.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1980

Torque control for electric motors

Method for adjusting electric-motor torque output to accomodate various loads utilizes phase-lock loop to control relay connected to starting circuit. As load is imposed, motor slows down, and phase lock is lost. Phase-lock signal triggers relay to power starting coil and generate additional torque. Once phase lock is recoverd, relay restores starting circuit to its normal operating mode.

Bernard, C. A.↗
NASA NTRS1973

Code regenerative clean-up loop transponder for a mu-type ranging system

A loop transponder for regenerating the code of a mu type ranging system is disclosed. It includes a phase locked loop, a code generator, and a loop detector. The function of the phase locked loop is to provide phase lock between a received component wk of the range signal and a replica rafter wk of the received component, provided by the code generator. The code generator also provides a replica of the next component rafter w(w+1). The loop detector responds to wk rafler wk and rafter w(k+1) to determine when the next component w(k+1) is received and controls the code generator to supply w(k+1) to the phase locked loop and to generate a replica rafter w(k+2) of the next component.

Hurd, W. J.↗
NASA NTRS1985

Nondestructive ultrasonic measurement of bolt preload using the pulsed-phase locked-loop interferometer

Achieving accurate preload in threaded fasteners is an important and often critical problem which is encountered in nearly all sectors of government and industry. Conventional tensioning methods which rely on torque carry with them the disadvantage of requiring constant friction in the fastener in order to accurately correlate torque to preload. Since most of the applied torque typically overcomes friction rather than tensioning the fastener, small variations in friction can cause large variations in preload. An instrument called a pulsed phase locked loop interferometer, which was recently developed at NASA Langley, has found widespread use for measurement of stress as well as material properties. When used to measure bolt preload, this system detects changes in the fastener length and sound velocity which are independent of friction. The system is therefore capable of accurately establishing the correct change in bolt tension. This high resolution instrument has been used for precision measurement of preload in critical fasteners for numerous applications such as the space shuttle landing gear and helicopter main rotors.

Allison, S. G.↗
NASA NTRS1973

Telecommunication systems engineering

Telecommunication network concepts are discussed together with carrier-tracking loops employing the phase-lock principle, phase and Doppler measurements in two-way phase-coherent tracking systems, range measurements by phase-coherent techniques, and questions of phase-coherent detection with perfect reference signals and with noisy reference signals. The design of one-way and two-way phase-coherent communication systems is considered, giving attention to the optimal design of single-channel systems, the design of two-channel systems, and the design of multichannel systems. Other topics explored include the design and the performance of phase-coherent systems preceded by band-pass limiters, symbol synchronization and its effects on data detection, noncoherent communication over the Gaussian channel, and tracking loops with improved performance.

Lindsey, W. C.↗
NASA NTRS2017

NASA GSFC Report on CCSDS Recommendations 2.1.8A B Minimum Earth Station Transmitter Frequency Resolution for Spacecraft Receiver Acquisition

In Fall 2016, ESA presented paper SLS-RFM 16-10 documenting a possible issue with the frequency lock-in range specification in Recommendation 2.1.8A of typically 267 to 1067 Hz in considerings (b) from considerings (a) for loop bandwidths [2B(sub LO)] in the range of 200 to 800 Hz with a recommendation of 100 Hz step size for frequency sweeping. The paper calculated the lock-in range to be (+/-)266 to (+/-)1064 rad/s or (+/-)42 to (+/-)168 Hz. Also, Recommendation 2.1.8B has the same issue for considering (a) and (b), i.e. for 2B(sub LO) =10 Hz, a lock-in range of 13 Hz was specified and a recommendation of 5 Hz step size for frequency sweeping. ESA also provided test results from the Rosetta and Exomars transponders. The results were somewhat inconsistent since the tests to verify lock-in and pull-in range did not include acquisition time, which is vital to the definition of these performance measures. This paper will address these test results below. However, we first examine the rationale for Recommendation 2.1.8A/B and its consistency with the theory of 2nd order phase lock loop operations. Our approach is to design a digital phase locked loop (DPLL) from phase locked loop (PLL) requirements. All analysis will be performed with a DPLL.

digital phase locked loop↗
NASA NTRS2000

A New Interferometer for Monitoring Atmospheric Phase Fluctuations

Water vapor in the Earth's troposphere introduces an extra electrical path in the propagation of radio signals through the atmosphere. The distribution of water vapor is irregular and distorts the wavefronts of incoming radio waves, limiting the angular resolution that can be achieved with ground-based telescopes. The level of fluctuations depends both on the location of the site ,and on the prevailing atmospheric conditions. The ability to measure the fluctuations is therefore important when choosing a site for a new instrument, and for scheduling observations of existing telescopes. Existing phase monitors are radio interferometers that monitor monochromatic beacon tones from geostationary communications satellites at a frequency of about 12 GHz. They have a classical heterodyne design based on two satellite receiving antennas; each has a front-end for amplifying and down-converting the incoming signals using a local oscillator that is phase-locked to a common reference frequency. In addition to multiple phase-locked loops these instruments require expensive phase-stable cabling to reduce the effects of thermal drift. The new system uses two consumer 18" digital satellite TV dishes to monitor satellite TV broadcast signals over a bandwidth of 500 MHz (12.2 to 12.7 GHz). The novel design eliminates the need for phase-locked loops and thermally stable components, and uses a pair of Gilbert Cell multipliers to perform the broadband correlation. A phase monitor has been been built and deployed at the site of the Berkeley-Illinois-Maryland Association Millimeter Array in Northern California, and has been operating successfully since June 1998, measuring the difference in electrical path length for parallel lines of sight to the satellite separated by a baseline of 100 m. With a hardware cost of approximately $4000, it is much cheaper than previous instruments, and the low power requirements and high reliability make the system suitable for site testing in remote locations.

Lay, Oliver↗
NASA NTRS1981

Investigation of air transportation technology at Ohio University, 1980

Specific configurations of first and second order all digital phase locked loops were analyzed for both ideal and additive gaussian noise inputs. In addition, a design for a hardware digital phase locked loop capable of either first or second order operation was evaluated along with appropriate experimental data obtained from testing of the hardware loop. All parameters chosen for the analysis and the design of the digital phase locked loop were consistent with an application to an Omega navigation receiver although neither the analysis nor the design are limited to this application. For all cases tested, the experimental data showed close agreement with the analytical results indicating that the Markov chain model for first and second order digital phase locked loops are valid.

Mcfarland, R. H.↗
NASA NTRS2010

Closed-Loop Control of Vortex Formation in Separated Flows

In order to phase lock the flow at the desired shedding cycle, particularly at Phi,best, We designed a feedback compensator. (Even though the open-loop forcing at Wf below Wn can lead to phase-locked limit cycles with a high average lift,) This feedback controller resulted in the phase-locked limit cycles that the open-loop control could not achieve for alpha=30 and 40 Particularly for alpha=40, the feedback was able to stabilize the limit cycle that was not stable with any of the open-loop periodic forcing. This results in stable phase-locked limit cycles for a larger range of forcing frequencies than the open-loop control. Also, it was shown that the feedback achieved the high-lift unsteady flow states that open-loop control could not sustain even after the states have been achieved for a long period of time.

Colonius, Tim↗