Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Frequency modulation”

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 577 records · Page 32
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

On-Chip Cavity Electroacoustics Using Lithium Niobate Phononic Crystal Resonators

Mechanical systems are pivotal in quantum technologies because of their long coherent time and versatile coupling to qubit systems. So far, the coherent and dynamic control of gigahertz-frequency mechanical modes mostly relies on optomechanical coupling and piezoelectric coupling to superconducting qubits. Here, we demonstrate on-chip cavity electroacoustic dynamics using our microwave-frequency electrically modulated phononic crystal resonators on lithium niobate. Leveraging the high dispersion of phononic crystal, our acoustic modes space unevenly in the frequency spectrum, emulating atomic energy levels. Atomiclike transitions between different acoustic modes are selectively achieved by applying electrical fields to modulate acoustic modes via the nonlinear piezoelectricity of lithium niobate. Among two modes, we demonstrate Autler-Townes splitting, ac Stark shift, and Rabi oscillation with a maximum cooperativity of 4.18. Extending to three modes, we achieve nonreciprocal frequency conversions with an isolation up to 20 dB. Nonreciprocity can be tuned by the time delay between the two modulating pulses. Finally, our cavity electroacoustic platform could find broad applications in sensing, microwave signal processing, acoustic computing, and quantum acoustics.

Rabi model↗
DOE OSTI2025

Gigahertz-frequency acousto-optic phase modulation of visible light in a CMOS-fabricated photonic circuit

Optical phase modulators operating at visible wavelengths are essential components for photonic technologies such as those for quantum control, communications, and laser ranging. However, they remain challenging to implement in scalable, integrated platforms capable of handling high optical powers. Here we present a visible-light, gigahertz-frequency acousto-optic phase modulator, fabricated on a 200-mm wafer in a volume CMOS foundry, that supports greater than 500 mW of optical power at 730 nm. The device combines a piezoelectric transducer and a photonic waveguide within a single, wavelength-scale structure that confines both a propagating optical mode and an electrically excitable breathing-mode mechanical resonance. By tuning the device’s geometry to optimize the optomechanical interaction, we achieve modulation depths up to 4.85 rad with 80 mW of applied microwave power at 2.31 GHz in a 2-mm-long device. This corresponds to resonant modulation figures of merit of V π = 1.32V and V π ⋅ L = 0.26V cm. To our knowledge, this is the lowest V π ever demonstrated in any acousto-optic phase modulator and represents a 15-fold reduction in V π and a 100-fold reduction in required microwave power relative to state-of-the-art modulators with high visible-wavelength power handling commonly employed in quantum control systems.

Freedman, Jacob M. [Univ. of Arizona, Tucson, AZ (↗
DOE OSTI2021

Online Detection of Low-Quality Synchrophasor Data Considering Frequency Similarity

Here, this letter proposes a new approach for online detection of low-quality synchrophasor data under both normal and event conditions. The proposed approach utilizes the features of synchrophasor data in time and frequency domains to distinguish multiple regional PMU signals and detect low-quality synchrophasor data. It is more effective to detect low-quality data with apparently indistinguishable profiles. Case studies from recorded synchrophasor measurements verify the effectiveness of the proposed approach for detecting low-quality synchrophasor data in frequency, voltage magnitude and voltage angle.

42 ENGINEERING↗
DOE OSTI2020

An ultrafast laser pulse picker technique for high-average-current high-brightness photoinjectors

Beam diagnostics in high brightness photoinjectors requires that optical pulses from a high-power drive laser be picked up with an ultrahigh pulse contrast ratio and without temporal profile distortion. In high-average-current high-brightness photoinjectors, high-power drive lasers are routinely operated at GHz-level pulse repetition rate and it is challenging to achieve pulse picking without any pulse distortion. Here, we report on a new ultrafast pulse picker technique for beam diagnostics in high-average-current high-brightness photoinjectors. By efficiently combining an ultrafast low-power electro-optic modulator, high-power fiber laser amplifiers, a high-power Pockels Cell, and a frequency doubling module, we have successfully demonstrated optical bunch (30 pulses per bunch) pickup from a 704 MHz high-power drive laser and achieved a 10 6 :1 pulse contrast ratio and nearly zero pulse distortion. The performance of this pulse picking technique has been verified through beam characterization and electron cooling in the low energy RHIC electron cooling accelerator at Brookhaven National Laboratory.

43 PARTICLE ACCELERATORS↗
DOE OSTI2024

Temporal light modulation: A phantom array visibility measure

At temporal light modulation (TLM) frequencies between 80 Hz and 20 000 Hz observers may perceive a series of repeated images called the phantom array effect (PAE) when they move their eyes in large saccades across a modulating light source or across a scene lit by the modulating light source. To date, there is no well-established measure for quantifying PAE visibility, but there is growing awareness of the need for one among design professionals and sensitive populations. This paper documents a new measure, the phantom array visibility measure (PAVM), which is based on the results of recent human factors experiments. The measure follows the mathematical underpinning used by the flicker visibility measure and the stroboscopic visibility measure, where the time-domain TLM waveform is converted into its Fourier frequency components; each component is evaluated through a threshold curve of modulation depth, then summed through an equation employing a Minkowski exponent. This scales the PAVM so that a value of 1 indicates a waveform at a threshold visibility in the conditions of the underlying experiment.

Tan, J.↗
NASA NTRS1984

Method and apparatus for pulse width modulation control of an AC induction motor

An inverter is connected between a source of DC power and a three-phase AC induction motor, and a micro-processor-based circuit controls the inverter using pulse width modulation techniques. In the disclosed method of pulse width modulation, both edges of each pulse of a carrier pulse train are equally modulated by a time proportional to sin .THETA., where .THETA. is the angular displacement of the pulse center at the motor stator frequency from a fixed reference point on the carrier waveform. The carrier waveform frequency is a multiple of the motor stator frequency. The modulated pulse train is then applied to each of the motor phase inputs with respective phase shifts of 120.degree. at the stator frequency. Switching control commands of electronic switches in the inverter are stored in a random access memory (RAM) and the locations of the RAM are successively read out in a cyclic manner, each bit of a given RAM location controlling a respective phase input of the motor. The DC power source preferably comprises rechargeable batteries and all but one of the electronic switches in the inverter can be disabled, the remaining electronic switch being part of a flyback DC-DC converter circuit for recharging the battery.

Geppert, Steven↗
NASA NTRS1985

Pulse width modulation inverter with battery charger

An inverter is connected between a source of DC power and a three-phase AC induction motor, and a microprocessor-based circuit controls the inverter using pulse width modulation techniques. In the disclosed method of pulse width modulation, both edges of each pulse of a carrier pulse train are equally modulated by a time proportional to sin .theta., where .theta. is the angular displacement of the pulse center at the motor stator frequency from a fixed reference point on the carrier waveform. The carrier waveform frequency is a multiple of the motor stator frequency. The modulated pulse train is then applied to each of the motor phase inputs with respective phase shifts of 120.degree. at the stator frequency. Switching control commands for electronic switches in the inverter are stored in a random access memory (RAM) and the locations of the RAM are successively read out in a cyclic manner, each bit of a given RAM location controlling a respective phase input of the motor. The DC power source preferably comprises rechargeable batteries and all but one of the electronic switches in the inverter can be disabled, the remaining electronic switch being part of a flyback DC-DC converter circuit for recharging the battery.

Slicker, James M.↗
NASA NTRS1989

Measuring Tension In A Tether

Proposed instrument measures tension in tether and transmits data on tension so tension monitored or adjusted as necessary. Positioned along length of tether, which measures tension only at ends. Device includes strain gauge to sense tension. Output of strain gauge controls modulation of battery- or solar-powered radio transmitter. In another version, transmitter receives radio signal on one frequency and returns signal on another frequency with modulation signifying tension. Yet another version, data on tension carried on beam of light. Laser-diode transmitter powered by battery, radio beam, beam of light, or solar energy.

Hinman, E. M.↗
NASA NTRS1972

Encoding and decoding of color information using two-dimensional spatial filtering.

Spatial frequency encoding is described as it applies to both photographic and television systems. In each case, color separations amplitude modulate spatial frequency carriers. The photographic system separates the carriers in the two-dimensional Fourier transform plane using coherent optics; the television system employs a two-dimensional electrical filter to perform the same separation. These filters are synthesized so that the two-dimensional bandwidths of the television camera are used efficiently. Nonlinear processing techniques are also described to minimize crosstalk between channels.

Schaefer, L. F.↗
NASA NTRS1980

A study of universal modulation techniques applied to satellite data collection

A universal modulation and frequency control system for use with data collection platform (DCP) transmitters is examined. The final design discussed can, under software/firmwave control, generate all of the specific digital data modulation formats currently used in the NASA satellite data collection service and can simultaneously synthesize the proper RF carrier frequencies employed. A novel technique for DCP time and frequency control is presented. The emissions of NBS radio station WWV/WWVH are received, detected, and finally decoded in microcomputer software to generate a highly accurate time base for the platform; with the assistance of external hardware, the microcomputer also directs the recalibration of all DCP oscillators to achieve very high frequency accuracies and low drift rates versus temperature, supply voltage, and time. The final programmable DCP design also employs direct microcomputer control of data reduction, formatting, transmitter switching, and system power management.

Source record↗
NASA NTRS2002

Discovery of a 450 Hz Quasi-Periodic Oscillation from the Microquasar GRO J1655-40 with the Rossi X-ray Timing Explorer

We report the discovery with the Proportional Counter Array on board the Rossi X-Ray Timing Explorer of a 450 Hz quasi-periodic oscillation (QPO) in the hard X-ray flux from the Galactic microquasar GRO J1655-40. This is the highest frequency QPO modulation seen to date from a black hole. The QPO is detected only in the hard X-ray band above approx. 13 keV. It is both strong and narrow, with a typical rms (root mean square) amplitude of 4.5% in the 13-27 keV range and a width of approx. 40 Hz (FWHM). For two observations in which we detect the 450 Hz QPO, a previously known approx. 300 Hz QPO is also observed in the 2-13 keV band. We show that these two QPOs sometimes appear simultaneously, thus demonstrating the first detection of a pair of high-frequency QPOs in a black hole system. Prior to this, pairs of high-frequency QPOs have been detected only in neutron star systems. GRO J1655-40 is one of only a handful of black hole systems with a good dynamical mass constraint. For a nonrotating black hole with mass between 5.5 and 7.9 solar masses, the innermost stable circular orbit (ISCO) ranges from 45 to 70 km. For any mass in this range the radius at which the orbital frequency reaches 450 Hz is less than the ISCO radius, indicating that, if the modulation is caused by Kepler motion, the black hole must have appreciable spin. If the QPO frequency is set by the orbital frequency of matter at the ISCO, then for this mass range the dimensionless angular momentum lies in the range 0.15 < j < 0.5. Moreover, if the modulation is caused by oscillation modes in the disk or Lense-Thirring precession, then this would also require a rapidly rotating hole. We briefly discuss the implications of our findings for models of X-ray variability in black holes and neutron stars.

Strohmayer, Tod E.↗
NASA NTRS2010

About the Compatibility of DORIS and VLBI Observations

We investigated the compatibility of the DORIS and VLBI observations at Badary Observatory. The DORIS beacon stands at 100-m distance from the main radio telescope dish and transmits signals on two frequencies: 2036.25 MHz and 401.25 MHz. The latter frequency is modulated to send messages containing an ID number, timing information, data from the meteorological sensors, and engineering data (e.g., power). Both frequencies affect the S/X band radio telescope receivers. The parameters of the DORIS signals were measured at the outputs of the S/X band intermediate frequency amplifier. It was found that: (1) The level of RFI, produced by the DORIS beacon, practically corresponds to the level of the system (antenna plus receiver) noise signal and does not overload the S/X band receivers. (2) The DORIS 401.25 MHz signal is out of the frequency bands recorded during standard VLBI sessions. As a result, RFI from DORIS does not affect VLBI observations. This conclusion was confirmed after data correlations of actual VLBI observations that were conducted with the DORIS beacon turned on/off.

Il'in, Gennady↗
NASA NTRS1986

Analysis of Jovian decametric data: Study of radio emission mechanisms

Catalogues of approx. 200 decametric arcs and approx. 200 gaps between arcs were studied, in an effort to reconcile the data with predictions for the model wherein reflections of Io-induced currents each emit in a conical pattern and yield a distinct radio arc. The most recent interpretations of this data suggest that these Io-produced Alfven waves persist for at least one or two passages of Io, and that the emission cone half angles are approx. 40 to 90 deg., varying from arc to arc. Below 1.2 MHz it was discovered that Jupiter emits radiation strongly modulated in frequency with periods of approx. 200 kHz; this quasi-sinusoidal emission (MSA) can shift more than 180 deg. in phase over periods of 6 seconds, although these shifts are usually much smaller. MSA is not strongly correlated with the longitudes of Io or Jupiter, and typically occurs in patches covering approx. 500 kHz or more for periods of a few minutes. Furthermore, this modulation sometimes resembles a train of impulses in frequency with exponential decays toward high frequencies. Comparison of these results with the previous studies of V-shaped S-bursts is suggestive of an emission mechanism.

Staelin, D. H.↗
NASA NTRS1989

High stability radio links

Radio telecommunication links are used for communication with deep space probes. These links consist of sinusoidal carrier signals at radio frequencies (RF) modulated with information sent between the spacecraft and the earth. This carrier signal is a very pure and stable sinusoid, typically derived from an atomic frequency standard whose frequency and phase are used to measure the radial velocity of the probe and from this and other data types derive its trajectory. This same observable can be used to search for space-time distortions cased by low frequency (0.1 to 100 MHz) gravitation radiation. How such a system works, what its sensitivity limitations are, and what potential future improvements can be made are discussed.

Kursinski, E. Robert↗
NASA NTRS2011

Receiver Signal to Noise Ratios for IPDA Lidars Using Sine-wave and Pulsed Laser Modulation and Direct Detections

Integrated path differential absorption (IPDA) lidar can be used to remotely measure the column density of gases in the path to a scattering target [1]. The total column gas molecular density can be derived from the ratio of the laser echo signal power with the laser wavelength on the gas absorption line (on-line) to that off the line (off-line). 80th coherent detection and direct detection IPDA lidar have been used successfully in the past in horizontal path and airborne remote sensing measurements. However, for space based measurements, the signal propagation losses are often orders of magnitude higher and it is important to use the most efficient laser modulation and detection technique to minimize the average laser power and the electrical power from the spacecraft. This paper gives an analysis the receiver signal to noise ratio (SNR) of several laser modulation and detection techniques versus the average received laser power under similar operation environments. Coherent detection [2] can give the best receiver performance when the local oscillator laser is relatively strong and the heterodyne mixing losses are negligible. Coherent detection has a high signal gain and a very narrow bandwidth for the background light and detector dark noise. However, coherent detection must maintain a high degree of coherence between the local oscillator laser and the received signal in both temporal and spatial modes. This often results in a high system complexity and low overall measurement efficiency. For measurements through atmosphere the coherence diameter of the received signal also limits the useful size of the receiver telescope. Direct detection IPDA lidars are simpler to build and have fewer constraints on the transmitter and receiver components. They can use much larger size 'photon-bucket' type telescopes to reduce the demands on the laser transmitter. Here we consider the two most widely used direct detection IPDA lidar techniques. The first technique uses two CW seeder lasers, one on-line and one offline that are intensity modulated by two different frequency sine-waves signals before being amplified by a common laser amplifier. The receiver uses narrowband amplitude demodulation, or lock-in, Signal processing at the given laser modulation frequencies [3,4]. The laser transmitter operates in a quasi CW mode with the peak power equal to twice the average power. The on-line and off-line lasers can be transmitted at the same time without interference. Another direct detection technique uses a low duty cycle pulsed laser modulation [5,6] with the laser wavelengths alternating between on-line and off-line on successive pulses. The receiver uses time resolved detection and can also provide simultaneous target range measurement. With a lower laser duty cycle it requires a much higher peak laser power for the same average power.

Sun, Xiaoli↗
NASA NTRS1965

Reducing distortion in an fm modulator.

Free-running oscillator incorporating correction circuit to improve linearity of voltage-variable capacitor for reducing second harmonic and intermodulation distortion

FREQUENCY MODULATION↗