Search NASA⌕ Search

SEARCH · Search NASA

Results for “CARRIER FREQUENCY”

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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Clock synchronization experiments using OMEGA transmissions

The OMEGA transmissions from North Dakota on 13.10 and 12.85 kHz were monitored at several sites using a recently developed OMEGA timing receiver specifically designed for this purpose. The experiments were conducted at Goddard Space Flight Center, Greenbelt, Maryland; U.S. Naval Observatory, Washington, D.C.; and at the NASA tracking station, Rosman, North Carolina. Results show that cycle identification of the two carrier frequencies was made at each test site, thus, coarse time (76 microseconds) from the OMEGA transmitted signals to within the ambiguity period of each OMEGA frequency was extracted. The fine time determination, which was extracted from the phase difference between the received OMEGA signals and locally generated signals, was about + or - 2 microseconds for daytime reception and about + or - 5 microseconds for nighttime reception.

Chi, A. R.↗
NASA NTRS1974

Signal simulator model A-111

A signal simulator designed to function as a signal source for Doppler tracking high data rate receivers is described. The simulator produces modulated signals whose carrier frequency can be varied between 200 and 900 MHz at rates greater than 20 MHz/sec. The modulation is phase shift keying with data rate up to 300 megabits per second.

Flattau, T.↗
NASA NTRS1974

Wideband infrared receiver backend

The design, operation, and configuration of the receiver backend for a wideband infrared tracking receiver are described. A squaring loop is incorporated into the receiver design to enable it to track the Doppler shifted carrier which is Phase Shift Keyed modulated. The receiver has a 400 MHz instantaneous bandwidth and tracks signals whose carrier frequency at the backend input is between 200 and 900 MHz with frequency variation rates greater than 20 MHz/second. The output data is compatible with MECL 3 logic.

Flattau, T.↗
NASA NTRS1975

A study of the use of vibration and stress wave sensing for the detection of bearing failure

Results from an experimental study of vibrations and stress waves emitted from ball bearings are presented. Fatique tests were run with both high quality bearings and man faulted bearings, all of one size. Tests were instrumented with different sensors to detect the noises from 10 Hz to 1 MHz. Frequency spectrum plots are presented. The modulation characteristics of the ultrasonic noises were analyzed, and acoustic emission type measurements were conducted. Results are presented which show that there are usable acoustic signal levels even beyond 500 KHz. These signal levels are modulated by a low frequency carrier which is a function of the stress loading and acoustic transmissibility. The results were correlated to fault size in the bearings. The correlation shows that the sensor used for signals from 100 KHz to 1 MHz gave the best sensitivity and detected the generation of very small spalls or pits.

Ensor, L. C.↗
NASA NTRS1977

GEOS-3 Doppler difference tracking

The Doppler difference method as applied to track the GEOS 3 spacecraft is discussed. In this method a pair of 2 GHz ground tracking stations simultaneously track a spacecraft beacon to generate an observable signal in which bias and instability of the carrier frequency cancel. The baselines are formed by the tracking sites at Bermuda, Rosman, and Merritt Island. Measurements were made to evaluate the effectiveness of the Doppler differencing procedure in tracking a beacon target with the high dynamic rate of the GEOS 3 orbit. Results indicate the precision of the differenced data to be at a level comparable to the conventional precise two way Doppler tracking.

Rosenbaum, B.↗
NASA NTRS1978

Direct-reading group-delay measurement

Technique for measuring modulation signal retardation in microwave components gives direct plot of dependence of delay time on carrier frequency. Recorder sensitivity can be adjusted to give convenient scale factor for group delay. From family of such recordings, it is possible to observe changes in group delay due to temperature, mechanical stress, and other factors.

Trowbridge, D. L.↗
NASA NTRS1980

Pioneer Saturn celestial mechanics experiment

The paper investigates a continuous round-trip radio link at S band (2.2 GHz) that was maintained during the Pioneer Saturn encounter between stations of the Deep Space Network and the spacecraft. From an analysis of the Doppler shift in the radio carrier frequency, a number of gravitational effects on the trajectory were determined. Gravitational moments for Saturn were found from a preliminary analysis, as well as mass values for the Saturn satellites Rhea, Iapetus, and Titan. It was determined that the densities of all three satellites are low and consistent with the compositions of ices. Theoretical calculations for the Saturn interior are described which use the latest observational data, including Pioneer Saturn and state-of-the-art physics for the internal composition.

Anderson, J. D.↗
NASA NTRS1979

The Surface Contour Radar, a unique remote sensing instrument

A 36 GHz computer controlled airborne Surface Contour Radar (SCR) is described, which was developed by the Naval Research Laboratory and NASA. The system uses pulse-compression techniques and dual frequency carriers spaced far enough apart to be decorrelated on the sea surface. The continuous wave transmitter is biphase modulated, the return signal is autocorrelated, and the code length and clock rate are variable, providing selectable range resolutions of 0.15, 0.30, 0.61 and 1.52 m. The SCR generates a false-color coded elevation map of the sea surface below the aircraft in real time, and can routinely produce ocean directional wave spectra with off-line data processing.

Kenney, J. E.↗
NASA NTRS1981

DSN command system

Modification of the currently operational DSN Command System MK 3-80 consisted of improvement of the uplink carrier frequency tuning capability to satisfy Voyager 2 requirements. Upgrading of Command System monitoring functions in the Network Operations Control Center is discussed. The DSN Command System requirements and functional design are described for the Mark 4 Network.

Thorman, H. C.↗
NASA NTRS1980

Centered CW interference rejection using spread spectrum techniques

A mathematical model is developed for the rejection of CW interference by spread spectrum techniques. When this interference is known to be exactly at the carrier frequency of the spread spectrum signal, this information can be used to design optimal IF filtering prior to despreading. The application of this approach to the pilot beam receiver of the Solar Power Satellite is considered as an example.

Scholtz, R. A.↗
NASA NTRS1981

GPS aiding of ocean current determination

The navigational accuracy of an oceangoing vessel using conventional GPS p-code data is examined. The GPS signal is transmitted over two carrier frequencies in the L-band at 1575.42 and 1227.6 MHz. Achievable navigational uncertainties of differenced positional estimates are presented as a function of the parameters of the problem, with particular attention given to the effect of sea-state, user equivalent range error, uncompensated antenna motion, varying delay intervals, and reduced data rate examined in the unaided mode. The unmodeled errors resulting from satellite ephemeris uncertainties are shown to be negligible for the GPS-NDS (Navigation Development) satellites. Requirements are met in relatively calm seas, but accuracy degradation by a factor of at least 2 must be anticipated in heavier sea states. The aided mode of operation is examined, and it is shown that requirements can be met by using an inertial measurement unit (IMU) to aid the GPS receiver operation. Since the use of an IMU would mean higher costs, direct Doppler from the GPS satellites is presented as a viable alternative.

Mohan, S. N.↗
NASA NTRS1982

Sound broadcasting satellite systems for individual reception by mobile receivers

In this paper, the feasibility of a multi-channel sound broadcasting satellite system for operation in a band between 0.5 and 2.0 GHz is investigated. Considered are sound broadcasting satellite systems that provide conventional FM sound broadcasting for individual receivers in a wide geographical area. Comparative weight estimation of sound broadcasting satellites is carried out for various sizes of coverage area and spacecraft antenna, and for different carrier frequencies in the band from 0.5 to 2.0 GHz. It is concluded that relatively light (1200 to about 1500 lbs) spacecraft are feasible, even with low-cost portable or mobile receiving systems.

Park, Y. H.↗
NASA NTRS1983

Triangular system solutions on an optical systolic processor

It is noted that the simplified system of equations presented by Casasent and Ghosh (1983) can also be solved optically. One realization of this is described, with attention given to data flow and speed for the case of a lower triangular system of equations. The solution of an upper triangular system of equations can be handled in analogous fashion. The problem requires a matrix-vector processor. Only one carrier frequency input to the acoustooptic cell and only one output detector are used. To multiply a matrix by a vector in this system, the time-multiplexed vector elements are fed into the acoustooptic cell.

Ghosh, A.↗
NASA NTRS1985

Discriminator Aids Phase-Lock Acquisition

Voltage-controlled oscillator in suppressed-carrier detector acquire carrier frequency and phase quickly with help of frequency-discriminator arrangement. To obtain discriminator function, filter bandwidth in quadrature (Q) leg of detector is widened with respect to bandwidth of filter in inphase (l) leg.

Carson, L. M.↗
NASA NTRS1985

Calibrating for Ionospheric Phase Delays

Technique determines ionospheric phase delay on real-time universally applicable basis in terms of electrons per meter squared by coherently modulating two L-band carrier frequencies received from two Global Positioning System satelites. Two pseudorandom number sequences cross-correlated to derive delay time.

Macdoran, P. F.↗
NASA NTRS1983

Reflectance Measurements, Part 2

Improving the productivity of spectroreflectometer readings taken to monitor induced contamination of lenses, mirrors, and coatings in the space environment are described. More sophisticated modelling techniques were applied to the laboratory data collected last summer in order to produce a more accurate model of the nonlinearities and noise sources of the instrumentation. This would ultimately allow for correction of known anomalies by the digital computer, yielding an anticipated order to magnitude improvement in the accuracy of the reflectance measurements, while reducing the total measuring time. The construction of and programming for a modernized version of the electronics used in Beckman DK-2 spectroreflectometers suffered because of a schedule lag in fabrication of a modified form of the carrier frequency pickoff. Separate development of the electronics and the computer programming was partially accomplished.

Brown, R. A.↗
NASA NTRS1984

60-GHz integrated-circuit high data rate quadriphase shift keying exciter and modulator

An integrated-circuit quadriphase shift keying (QPSK) exciter and modulator have demonstrated excellent performance directly modulating a carrier frequency of 60 GHz with an output phase error of less than 3 degrees and maximum amplitude error of 0.5 dB. The circuit consists of a 60-GHz Gunn VCO phase-locked to a low-frequency reference source, a 4th subharmonic mixer, and a QPSK modlator packaged into a small volume of 1.8 x 2.5 x 0.35 in. The use of microstrip has the advantages of small size, light-weight, and low-cost fabrication. The unit has the potential for multigigabit data rate applications.

Grote, A.↗