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Graf, E. R.

Publications and source records attributed to Graf, E. R..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

The subsequence weight distribution of summed maximum length digital sequences

An attempt is made to develop mathematical formulas to provide the basis for the design of pseudorandom signals intended for applications requiring accurate knowledge of the statistics of the signals. The analysis approach involves calculating the first five central moments of the weight distribution of subsequences of hybrid-sum sequences. The hybrid-sum sequence is formed from the modulo-two sum of k maximum length sequences and is an extension of the sum sequences formed from two maximum length sequences that Gilson (1966) evaluated. The weight distribution of the subsequences serves as an approximation to the filtering process. The basic reason for the analysis of hybrid-sum sequences is to establish a large group of sequences with good statistical properties. It is shown that this can be accomplished much more efficiently using the hybrid-sum approach rather than forming the group strictly from maximum length sequences.

Weathers, G. D.↗
NASA NTRS1973

Statistical properties of filtered pseudorandom digital sequences formed from the sum of maximum-length sequences

The statistics of filtered pseudorandom digital sequences called hybrid-sum sequences, formed from the modulo-two sum of several maximum-length sequences, are analyzed. The results indicate that a relation exists between the statistics of the filtered sequence and the characteristic polynomials of the component maximum length sequences. An analysis procedure is developed for identifying a large group of sequences with good statistical properties for applications requiring the generation of analog pseudorandom noise. By use of the analysis approach, the filtering process is approximated by the convolution of the sequence with a sum of unit step functions. A parameter reflecting the overall statistical properties of filtered pseudorandom sequences is derived. This parameter is called the statistical quality factor. A computer algorithm to calculate the statistical quality factor for the filtered sequences is presented, and the results for two examples of sequence combinations are included. The analysis reveals that the statistics of the signals generated with the hybrid-sum generator are potentially superior to the statistics of signals generated with maximum-length generators. Furthermore, fewer calculations are required to evaluate the statistics of a large group of hybrid-sum generators than are required to evaluate the statistics of the same size group of approximately equivalent maximum-length sequences.

Wallace, G. R.↗
NASA NTRS1972

Television broadcast satellite systems, volume 1

Empirical expressions are derived to account for various components of the television satellite broadcast system. Computer programs are developed to determine the system weight in any general design. The factors of picture quality, propagation losses, and RF power requirements are discussed and determined.

Graf, E. R.↗
NASA NTRS1972

Television broadcast relay system, volume 2

A statistical analysis of propagation characteristics at 12 GHz for the design of a worldwide communication satellite system is reported. High power spaceborne TV transmitter design and the development of a low cost, low noise ground receiver for domestic reception are considered most important for implementation of a TVBS system.

Graf, E. R.↗
NASA NTRS1969

Improved VHF direction finding system

Direction finding device operating at very high frequencies requires a loop antenna, mechanical rotation, and large structures. The system is applicable to an unmanned configuration. Direction information is extracted in the form of a direction cosine analog.

Graf, E. R.↗
NASA NTRS1969

A thirty-six element array antenna system

Thirty-six element square array, with mutual coupling between crossed slots for array elements, is used as an electronically scanned tracking antenna. The system does not require the movement of the antenna or the presence of an operator.

Graf, E. R.↗