Sweep-frequency measurements of solar bursts.
Sweep-frequency measurements of solar nonthermal radio emissions in meter and decimeter wave ranges, discussing low RF spectrograph and interferometer observations
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Results for “RF Measurement”
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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Interferometer using RF switching matrix
Radio frequency switching technique for single receiver and data processing channel to be used for phase movement measurement is discussed. Components of interferometer radio frequency unit, X-band receiver, and interferometer data processing unit are illustrated. Elimination of major measurement error source is described.
Vanvleet, R. N.↗
Multiple-reflection conical microwave antenna
Conical-Gregorian antenna concept, using conical reflector, promises excellent rf performance and offers potential advantages in areas of mechanical and structural design, surface measurement, and in furlability. Multiple reflection scheme between one or more subreflectors and main reflector is utilized. Subreflector can be reduced to as little as 0.1 the diameter of main reflector.
Oliver, R. E.↗
Measurement of klystron phase modulation due to ac-powered filaments
A technique for determining the intermodulation components in the RF spectrum of the S-band radar transmitter generated by having the klystron filaments heated by 400-Hz ac power is described. When the klystron is being operated with 400-Hz (ac) on the filament, the IPM is buried in the 400-Hz equipment interference noise. The modulation sidebands were separated and identified and found to be-67 db below the main carrier. This is well below the transmitter specifications, and operating the filaments on ac would not degrade the spectrum to where it would be detrimental to the radiated RF.
Finnegan, E. J.↗
Precise Phase Comparator for Nearly Equal Frequencies
New circuit precisely compares phases of two RF signals nearly equal in frequency, such as two hydrogen-maser frequency standards. Measuring circuit minimizes interactions between two sources. Also stabilized against thermal effects and against noise that could produce erroneous readings. Heat sinking, buffer amplifiers, and low-noise zero-crossing detector make picosecond precision possible.
Reinhardt, V. S.↗
Atomic ion clock with two ion traps, and method to transfer ions
An atomic ion clock with a first ion trap and a second ion trap, where the second ion trap is of higher order than the first ion trap. In one embodiment, ions may be shuttled back and forth from one ion trap to the other by application of voltage ramps to the electrodes in the ion traps, where microwave interrogation takes place when the ions are in the second ion trap, and fluorescence is induced and measured when the ions are in the first ion trap. In one embodiment, the RF voltages applied to the second ion trap to contain the ions are at a higher frequency than that applied to the first ion trap. Other embodiments are described and claimed.
Prestage, John D.↗
Evaluate Techniques for Penetrating a Shielded Enclosure Using Twisted Pair Wire
The aim of this project is to demonstrate techniques for effectively penetrating a radio shielded enclosure using Ethernet cable (CAT-6). This process requires that we measure the shielding performance by means of testing and data orchestration to collect and analyze our data to present observations with different test cases. Each test case would represent a different penetration strategy that utilizes distinctive wire coupling and characteristics (i.e. the type of bulkhead link, the twist of each CAT-6 cable, the shielding type of each CAT-6 cable, and the length of the cable). As the different cable setups are fabricated a prototype evaluation of setup is conducted to measure the signal integrity of our testing configuration. Our signal integrity is measured through the analysis of different parameters found in the prototype evaluation such as RF leakage, impedance mismatch, and decay rate. As each of these data values are effectively collected and analyzed the most effective cable setup is selected based upon its ability to penetrate the shielded enclosure. The testing data is compared in conjunction with the cost of the manufacturing of the prototype wire penetration.
St. Julian, Christopher↗
Langmuir Probe Measurements of Inductively Coupled Plasmas in CF4/Ar/O2 Mixtures
Fluorocarbon gases, such as CF4, and their mixtures are widely used in contemporary low-pressure and high-density plasma processing techniques. In such plasmas Langmuir probe is one of the most commonly employed diagnostic techniques to obtain electron number density (ne), electron temperature (Te), electron energy distribution function (EEDF), mean electron energy (Ee), ion number density (ni), and plasma potential (Vp). In this paper we report probe data for planar inductively coupled plasmas in CF4/O2/Ar mixtures. By varying the relative concentrations in the mixture, radial profiles of ne, ni, Te, Ee, Vp, EEDF were measured in the mid-plane of the plasma at 10 mTorr and 20 mTorr of gas pressures, and 200 W and 300 W of RF powers. Data show that ne and ni decrease with increase of CF4 content and decrease of gas-pressure but they increase with increase of RF-power, whereas Vp increases with decrease of gas-pressure and remains independent of RF-power. However, they all peak at the center of the plasma and decrease towards the edge while Te follows the other way and increases a little with increase of power. The measured EEDFs exhibit Druyvesteyn-like distribution at all pressures and powers. Data are analyzed and will be presented.
Rao, M. V. V. S.↗
Design of a Combined Beacon Receiver and Digital Radiometer for 40 GHz Propagation Measurements at the Madrid Deep Space Communications Complex
NASA Glenn Research Center (GRC) and the Jet Propulsion Laboratory (JPL) have jointly developed an atmospheric propagation terminal to measure and characterize propagation phenomena at 40 GHz at the Madrid Deep Space Communications Complex (MDSCC) in Robledo de Chavela, Spain. The hybrid Q-band system utilizes a novel design which combines a 40 GHz beacon receiver and digital radiometer into the same RF front-end and observes the 39.402 GHz beacon of the European Space Agencys Alphasat Aldo Paraboni TDP5 experiment. Atmospheric measurements include gaseous absorption, rain fade, and scintillation. The radiometric measurement is calibrated by means of an included noise diode as well as tipping calibration. The goals of these measurements are to assist MDSCC mission operations as the facility increasingly supports Ka-band missions, as well as to contribute to the development and improvement of International Telecommunications Union (ITU) models for prediction of communications systems performance within the Q-band through the Aldo Paraboni Experiment. Herein, we provide an overview of the system design, characterization, and plan of operations which commenced at the MDSCC beginning in March 2017.
Radiowave Propagation↗
Thermal evaluation method for Klystron RF power
The feasibility of adding instrumentation to the cooling system of a microwave transmitter for use as a calorimetric power measurement calibration is examined. It considers the accuracy of the basic measurements as well as heat sources and losses not measured. Experimental results are presented in support of the theory.
Conroy, B. L.↗
Effect of reactor loading on atomic oxygen concentration as measured by NO chemiluminescence
It has previously been observed that the etch rate of polyethylene samples in the afterglow of an RF discharge in oxygen increases with reactor loading. This enhancement of the etch rate is attributed to reactive gas phase products of the polymer etching. In the present work, emission spectroscopy is employed to examine the species present in the gas phase during etching of polyethylene. In particular, the concentration of atomic oxygen downstream from the polyethylene samples is studied as a function of the reactor loading. It is found that the concentration of atomic oxygen increases as the reactor loading is increased. The increase of etch rate with increased reactor loading is attributed to the increase of atomic oxygen concentration in the vicinity of the sample.
Lerner, N. R.↗
Design of a Combined Beacon Receiver and Digital Radiometer for 40 GHz Propagation Measurements at the Madrid Deep Space Communications Complex
NASA Glenn Research Center (GRC) and the Jet Propulsion Laboratory (JPL) have jointly developed an atmospheric propagation terminal to measure and characterize propagation phenomena at 40 GHz at the Madrid Deep Space Communications Complex (MDSCC) in Robledo de Chavela, Spain. The hybrid Q-band system combines a 40 GHz beacon receiver and digital radiometer into the same RF front-end and observes the 39.402 GHz beacon of the European Space Agencys Alphasat Aldo Paraboni TDP5 experiment. The goals of these measurements are to assist MDSCC mission operations as well as to contribute to the development and improvement of International Telecommunications Union (ITU) models for prediction of communications systems performance within the Q-band. Herein, we provide an overview of the system design, characterization, and plan of operations to commence at the MDSCC beginning in March 2017.
Radio Attenuation↗
Parametric testing of an externally configured thermionic converter
A 25.4-cm long externally configured converter was performance tested by electrically heating the emitter to simulate reactor thermal power input. The measured maximum output power was limited by the maximum input power available from the electric RF induction heater. With maximum heater input power, the converter electric output was 178 W (1.95 W/sq cm) at an emitter temperature of 1946 K. This electric output power was smaller than expected. A reactor-core-length (25.4-cm long) cylindrical thermionic converter power and maintaining the emitter-to-collector gap without shorting are of major importance to the feasibility of a 25.4-cm-long reactor fuel element. The emitter of the converter is located externally to the collector to increase the fuel-volume fraction and to allow redundant collector cooling in a reactor configuration.
Shimada, K.↗
An active radar calibration target
An active radar calibrator (ARC), consisting of a receive antenna and a transmit antenna with an RF amplifier in between, is proposed as a tool for conducting high-precision calibration measurements of radar systems. The ARC can be designed to have a large radar cross-section with a broad pattern. Its major advantages over passive reflectors are its small physical size and its suitability for calibrating radars operating in a cross-polarized antenna configuration.
Brunfeldt, D. R.↗
Materials screening chamber for testing materials resistance to atomic oxygen
A unique test chamber for exposing material to a known flux of oxygen atoms is described. The capabilities and operating parameters of the apparatus include production of an oxygen atom flux in excess of 5 x 10 to the 16th atoms/sq cm-sec, controlled heating of the sample specimen, RF circuitry to contain the plasma within a small volume, and long exposure times. Flux measurement capabilities include a calorimetric probe and a light titration system. Accuracy and limitations of these techniques are discussed. An extension to the main chamber to allow simultaneous ultraviolet and atomic oxygen exposure is discussed. The oxygen atoms produced are at thermal energies. Sample specimens are maintained at any selected temperature between ambient and 200 C, to within + or - 2 C. A representative example of measurements made using the chamber is presented.
Pippin, H. G.↗
Linear ion trap based atomic frequency standard
In order to develop a trapped ion-based fieldable frequency standard with stability 1 x 10 to the -13th/sq rt tau for averaging times tau greater than 10,000 s, a hybrid RF/DC linear ion trap was developed which permits storage of large numbers of ions with reduced susceptibility to the second-order Doppler effect caused by the RF confining fields. The authors have confined Hg-199(+) ions in this trap and have measured very high Q transitions with good SNRs. In preliminary measurements they obtained stabilities of 1.6 x 10 to the -13th/sq rt tau (tau between 50 and 800 s) with a 160-mHz wide atomic resonance linewidth and a signal-to-noise ratio of 40 for each measurement cycle. Atomic resonance lines as narrow as 30 mHz on the 40.5-GHz clock transition have been measured with no appreciable reduction in the ion signal. A stability of 7 x 10 to the -14th/sq rt tau is made possible by the signal-to-noise and line Q of this measured transition. Analysis of fundamental sources of frequency instability indicates that a long-term stability of 2 x 10 to the -16th is feasible for this device with existing technology for tau = 10 to the 6th s or more.
Prestage, John D.↗
K- and Ka-band mobile-vehicular satellite-tracking reflector antenna system for the NASA ACTS mobile terminal
This paper describes the development of the K- and Ka-band mobile-vehicular satellite-tracking reflector antenna system for NASA's ACTS Mobile Terminal (AMT) project. ACTS is NASA's Advanced Communications Technology Satellites. The AMT project will make the first experimental use of ACTS soon after the satellite is operational, to demonstrate mobile communications via the satellite from a van on the road. The AMT antenna system consists of a mechanically steered small reflector antenna, using a shared aperture for both frequency bands and fitting under a radome of 23 cm diameter and 10 cm height, and a microprocessor controlled antenna controller that tracks the satellite as the vehicle moves about. The RF and mechanical characteristics of the antenna and the antenna tracking control system are discussed. Measurements of the antenna performance are presented.
Densmore, Art↗
RF Properties of Epitaxial Lift-Off HEMT Devices
Epitaxial layers containing GaAs HEMT and P-HEMT structures have been lifted-off the GaAs substrate and attached to other host substrates using an AlAs parting layer. The devices were on-wafer RF probed before and after the lift-off step showing no degradation in the measured S-parameters. The maximum stable gain indicates a low frequency enhancement of the gain of 1-2 dB with some devices showing an enhancement of F(sub max)F(sub T) consistently shows an increase of 12-20% for all lifted-off HEMT structures. Comparison of the Hall measurements and small signal models show that the gain is improved and this is most probably associated with an enhanced carrier concentration.
Young, Paul G.↗