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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1970

Noise bandwidth of common filters

Noise bandwidth of optimum second order and bandpass Butterworth, Bessel and Chebyshev filters for communication and radar systems

Adkins, A. F.↗
NASA NTRS1972

End-to-end RMS error testing on a constant bandwidth FM/FM system

End-to-end root-mean-square (rms) tests performed on a constant bandwidth FM/FM system with various settings of system parameters are reported. The testing technique employed is that of sampling, digitizing, delaying, and comparing the analog input against the sampled and digitized corresponding output. Total system error is determined by fully loading all channels with band-limited noise and conducting end-to-end rms error tests on one channel. Tests are also conducted with and without a transmission link and plots of rms errors versus receiver signal-to-noise (S/N) values are obtained. The combined effects of intermodulation, adjacent channel crosstalk, and residual system noise are determined as well as the single channel distortion of the system.

Wallace, G. R.↗
NASA NTRS1972

On the selection of a sampling filter bandwidth for a digital data detector.

Consideration of the problem of selecting a low-pass sampling bandwidth for the digital mechanization of a matched-filter bit-synchronizer combination. An attempt is made to determine how large a data rate can be provided for a fixed sampling rate (limited by hardware considerations on the sampling device) without paying an excessive penalty in SNR performance.

Simon, M. K.↗
NASA NTRS1973

Preemphasis for an S-band constant bandwidth FM/FM system.

Preemphasis schedules are given for 11 constant-bandwidth FM subcarriers modulating an S-band transmitter at various receiver SNRs (9 dB, 15 dB and 25 dB). The criterion for establishing these preemphasis curves is the achievement, at various receiver IF SNR, of equal receiver output SNR for all channels. The empirically derived results are compared with a simplified, analytically derived schedule and the primary differences are explained. The S-band preemphasis schedule is also found to differ from the lower frequency VHF case.

Wallace, G. R.↗
NASA NTRS1977

Application of a modified complementary filtering technique for increased aircraft control system frequency bandwidth in high vibration environment

A modified complementary filtering technique for estimating aircraft roll rate was developed and flown in a research helicopter to determine whether higher gains could be achieved. Use of this technique did, in fact, permit a substantial increase in system frequency bandwidth because, in comparison with first-order filtering, it reduced both noise amplification and control limit-cycle tendencies.

Garren, J. F., Jr.↗
NASA NTRS1977

Small-size 81- to 83.5-percent efficient 2- and 4-stage depressed collectors for octave-bandwidth high-performance TWT's

In a joint USAF-NASA Program, Lewis Research Center is carrying out an efficiency improvement program on traveling wave tubes for use in electronic counter measures by applying multistage depressed collector (MDC) and spent beam refocusing techniques. In the analytic part of the effort, three-dimensional electron trajectories are computed throughout the TWT. On the experimental side, tube performance is evaluated first without the MDC; then, the spent beam is analyzed for symmetry, circularity, and velocity spread. The three-dimensional theory predicts a MDC-efficiency, at mid-band, of 81 per cent for a 2-stage MDC with symmetric, circular, and optimally refocused beams and 85.5 per cent for a 4-stage MDC. Experimental results to date have yielded MDC efficiencies of a minimum of 81 and 83 per cent for a 2- and 4-stage MDC, respectively, across a one-octave bandwidth of a 4.8 to 9.6 GHz 330-to-550-W TWT.

Kosmahl, H. G.↗
NASA NTRS1979

Narrow-bandwidth receiver

Synchronous switching circuit reduces bandwidth and improves sensitivity of communications receiver. With modified receiver, signals 35 db below level can be detected.

Manus, E. A.↗
NASA NTRS1977

Sharing the 620-790 MHz band allocated to terrestrial television with an audio-bandwidth social service satellite system

A study was carried out to identify the optimum uplink and downlink frequencies for audio-bandwidth channels for use by a satellite system distributing social services. The study considered functional-user-need models for five types of social services and identified a general baseline system that is appropriate for most of them. Technical aspects and costs of this system and of the frequency bands that it might use were reviewed, leading to the identification of the 620-790 MHz band as a perferred candidate for both uplink and downlink transmissions for nonmobile applications. The study also led to some ideas as to how to configure the satellite system.

Smith, E. K.↗
NASA NTRS1977

Systems for measuring response statistics of gigahertz bandwidth photomultipliers

New systems have been developed for measuring the average impulse response, the pulse-height spectrum, the transit-time statistics as a function of signal level, and the dark-count spectrum of gigahertz bandwidth photomultipliers. Measurements showed that the 0.53 microns pulse used as an optical test source had a 30 picoseconds and less than 70 ps pulse width. Calibration data showed the system resolution to be less than 20 ps for root mean square transit-time measurements. Test data for a static crossed-field photomultiplier showed 2-photoelectron resolution and less than 30-ps time jitter over the 1- to 100-photoelectron range.

Abshire, J. B.↗