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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.

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At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Fiber-Optic Coupler And Dynamic-Range Enhancer For CARS

Simpler equipment yields higher coupling efficiency with fewer adjustments. In improved scheme for coupling coherent anti-Stokes Raman spectroscopy (CARS) signal from measurement volume to monochromator, optical fiber and two lenses used in place of previous system. Cylindrical lenses focus light from optical fiber into beam of approximately rectangular cross section at input plane of monochromator. Optical wedge diverts part of beam in monochromator to produce less-intense secondary image.

Cutler, Andrew D.↗
NASA NTRS1992

High-Dynamic-Range Fiber-Optic Link For Microwave Signals

Ultrastable fiber-optic communications system transmits microwave signals between antenna sites of Deep Space Network (DSN) and central processing station several kilometers away. Permits relocation of critical components from front-end areas of DSN antennas to central location, permitting radio-frequency (RF) antenna arraying, improving DSN flexibility, maintainability, and system performance. Also useful in commercial analog and digital communications.

Logan, Ronald T., Jr.↗
NASA NTRS2000

High Resolution and Large Dynamic Range Resonant Pressure Sensor Based on Q-Factor Measurement

A pressure sensor has a high degree of accuracy over a wide range of pressures. Using a pressure sensor relying upon resonant oscillations to determine pressure, a driving circuit drives such a pressure sensor at resonance and tracks resonant frequency and amplitude shifts with changes in pressure. Pressure changes affect the Q-factor of the resonating portion of the pressure sensor. Such Q-factor changes are detected by the driving/sensing circuit which in turn tracks the changes in resonant frequency to maintain the pressure sensor at resonance. Changes in the Q-factor are reflected in changes of amplitude of the resonating pressure sensor. In response, upon sensing the changes in the amplitude, the driving circuit changes the force or strength of the electrostatic driving signal to maintain the resonator at constant amplitude. The amplitude of the driving signals become a direct measure of the changes in pressure as the operating characteristics of the resonator give rise to a linear response curve for the amplitude of the driving signal. Pressure change resolution is on the order of 10(exp -6) torr over a range spanning from 7,600 torr to 10(exp -6) torr. No temperature compensation for the pressure sensor of the present invention is foreseen. Power requirements for the pressure sensor are generally minimal due to the low-loss mechanical design of the resonating pressure sensor and the simple control electronics.

Gutierrez, Roman C.↗
NASA NTRS2006

Motor Controller System For Large Dynamic Range of Motor Operation

A motor controller system uses a rotary sensor with a plurality of signal conditioning units, coupled to the rotary sensor. Each of these units, which is associated with a particular range of motor output shaft rotation rates, generate a feedback signal indicative of the position of the motor s output shaft. A controller (i) converts a selected motor output shaft rotation rate to a corresponding incremental amount of rotational movement for a selected fixed time period, (ii) selects, at periodic completions of the selected fixed time period, the feedback signal from one of the signal conditioning units for which the particular range of motor output shaft rotation rates associated therewith encompasses the selected motor output shaft rotation rate, and (iii) generates a motor drive signal based on a difference between the incremental amount of rotational movement and the feedback signal from the selected one of the signal conditioning Units.

Howard, David E.↗
NASA NTRS1994

Conductance measurement circuit with wide dynamic range

A conductance measurement circuit to measure conductance of a solution under test with an output voltage proportional to conductance over a 5-decade range, i.e., 0.01 uS to 1000 uS or from 0.1 uS to 10,000 uS. An increase in conductance indicates growth, or multiplication, of the bacteria in the test solution. Two circuits are used each for an alternate half-cycle time periods of an alternate squarewave in order to cause alternate and opposite currents to be applied to the test solution. The output of one of the two circuits may be scaled for a different range optimum switching frequency dependent upon the solution conductance and to enable uninterrupted measurement over the complete 5-decade range. This circuitry provides two overlapping ranges of conductance which can be read simultaneously without discontinuity thereby eliminating range switching within the basic circuitry. A VCO is used to automatically change the operating frequency according to the particular value of the conductance being measured, and comparators indicate which range is valid and also facilitate computer-controlled data acquisition. A multiplexer may be used to monitor any number of solutions under test continuously.

Mount, Bruce E.↗
NASA NTRS2001

Power supply with air core transformer and seperated power supplies for high dynamic range

A power supply for a quadrupole mass spectrometer which operates using an RF signal. The RF signal is controllable via a feedback loop. The feedback loop is from the output, through a comparator, and compared to a digital signal. An air core transformer is used to minimize the weight. The air core transformer is driven via two out of phase sawtooth signals which drive opposite ends of the transformer.

Chutjian, Ara↗
NASA NTRS2007

Increasing the dynamic range of CMOS photodiode imagers

A multiple-step reset process and circuit for resetting a voltage stored on a photodiode of an imaging device. A first stage of the reset occurs while a source and a drain of a pixel source-follower transistor are held at ground potential and the photodiode and a gate of the pixel source-follower transistor are charged to an initial reset voltage having potential less that of a supply voltage. A second stage of the reset occurs after the initial reset voltage is stored on the photodiode and the gate of the pixel source-follower transistor and the source and drain voltages of the pixel source-follower transistor are released from ground potential thereby allowing the source and drain voltages of the pixel source-follower transistor to assume ordinary values above ground potential and resulting in a capacitive feed-through effect that increases the voltage on the photodiode to a value greater than the initial reset voltage.

Pain, Bedabrata↗
NASA NTRS2007

Servomotor and Controller Having Large Dynamic Range

A recently developed micro-commanding rotational-position-control system offers advantages of less mechanical complexity, less susceptibility to mechanical resonances, less power demand, less bulk, less weight, and lower cost, relative to prior rotational-position-control systems based on stepping motors and gear drives. This system includes a digital-signal- processor (DSP)-based electronic controller, plus a shaft-angle resolver and a servomotor mounted on the same shaft. Heretofore, micro-stepping has usually been associated with stepping motors, but in this system, the servomotor is micro-commanded in response to rotational-position feedback from the shaft-angle resolver. The shaft-angle resolver is of a four-speed type chosen because it affords four times the resolution of a single-speed resolver. A key innovative aspect of this system is its position-feedback signal- conditioning circuits, which condition the resolver output signal for multiple ranges of rotational speed. In the preferred version of the system, two rotational- speed ranges are included, but any number of ranges could be added to expand the speed range or increase resolution in particular ranges. In the preferred version, the resolver output is conditioned with two resolver-to-digital converters (RDCs). One RDC is used for speeds from 0.00012 to 2.5 rpm; the other RDC is used for speeds of 2.5 to 6,000 rpm. For the lower speed range, the number of discrete steps of RDC output per revolution was set at 262,144 (4 quadrants at 16 bits per quadrant). For the higher speed range, the number of discrete steps per revolution was set at 4,096 (4 quadrants at 10 bits per quadrant).

Alhorn, Dean C.↗
NASA NTRS2007

High-Accuracy, High-Dynamic-Range Phase-Measurement System

A digital phase meter has been designed to satisfy stringent requirements for measuring differences between phases of radio-frequency (RF) subcarrier signals modulated onto laser beams involved in the operation of a planned space-borne gravitational-wave-detecting heterodyne laser interferometer. The capabilities of this system could also be used in diverse terrestrial applications that involve measurement of signal phases, including metrology, navigation, and communications.

Shaddock, Daniel↗
NASA NTRS2008

Large-Scale Structure of the Molecular Gas in Taurus Revealed by High Spatial Dynamic Range Spectral Line Mapping

Viewgraph topics include: optical image of Taurus; dust extinction in IR has provided a new tool for probing cloud morphology; observations of the gas can contribute critical information on gas temperature, gas column density and distribution, mass, and kinematics; the Taurus molecular cloud complex; average spectra in each mask region; mas 2 data; dealing with mask 1 data; behavior of mask 1 pixels; distribution of CO column densities; conversion to H2 column density; variable CO/H2 ratio with values much less than 10(exp -4) at low N indicated by UV results; histogram of N(H2) distribution; H2 column density distribution in Taurus; cumulative distribution of mass and area; lower CO fractional abundance in mask 0 and 1 regions greatly increases mass determined in the analysis; masses determined with variable X(CO) and including diffuse regions agrees well with the found from L(CO); distribution of young stars as a function of molecular column density; star formation efficiency; star formation rate and gas depletion; and enlarged images of some of the regions with numerous young stars. Additional slides examine the origin of the Taurus molecular cloud, evolution from HI gas, kinematics as a clue to its origin, and its relationship to star formation.

molecular clouds↗
NASA NTRS2021

A High Dynamic-Range Photon-Counting Receiver for Deep Space Optical Communication

The Deep Space Optical Communication (DSOC) project will demonstrate free-space optical communication at almost 3 AU, or 3 orders of magnitude further than any previous attempt. DSOC will utilize the 5m Palomar Hale Telescope to receive the downlink signal, which will couple the downlink light onto an optical table and into a superconducting nanowire single photon detector (SNSPD). The output of the SNSPD is digitized by the Ground Laser Receiver Signal Processing Assembly (GSPA) using a high throughput streaming time to digital converter (TDC). The GSPA is a scalable FPGA-based receiver which demodulates and decodes the DSOC downlink signal through novel signal processing algorithms implemented on Xilinx UltraScale+ FPGAs, as well as Python-based software monitor and control routines. Exploiting the unique TDC-based architecture, the GSPA supports over four orders of magnitude of downlink data rates across multiple orders of magnitude of signal and background powers. In this paper we present an overview of the hardware, firmware and software architectures to implement this system, as well as performance analysis for links ranging from near-Earth to 2.8 AU.

Srinivasan, Meera↗
NASA NTRS1971

Isosceles detector provides maximum resolution in expanded range

Dynamic range expansion system for radio frequency /RF/ signal detection equipment consists of RF amplifiers, RF amplitude modulated detectors, and operational amplifier. The analog output gives maximum resolution over fixed voltage range, without switching. Two minor drawbacks of this circuit are cited.

Watterson, R. F.↗