13 research outputs found
Cross-eye gain in multiloop retrodirective cross-eye jamming
The simultaneous use of multiple retrodirective
cross-eye jammers is analysed for both the case
where the jammer loops point in different directions and
when they point in the same direction. In both cases, the
use of multiple cross-eye jammer loops is shown to lead to
significantly increased angular errors in the threat radar
under certain conditions. Alternatively, the sum-channel
return can be increased to reduce the jammer-to-signal
ratio (JSR) requirements for each jammer loop.http://ieeexplore.ieee.org/xpl/RecentIssue.jsp?reload=true&punumber=7hb2016Electrical, Electronic and Computer Engineerin
The practical implementation of a retrodirective cross-eye jammer by using software defined radio (SDR)
Dissertation (MEng (Electronic Engineering))--University of Pretoria, 2022.Radar-guided missiles have the potential to cause extreme damage to vital military assets. Although
traditional deception techniques can deceive radars in range and Doppler shift, only a few methods can
deceive them in angle. Cross-eye jamming was identified as a possible countermeasure against angular
radar threats. This electronic attack (EA) method works by artificially creating the worst case of glint
in angular radars.
Numerous analyses of cross-eye jamming exist in the literature. The earlier analyses were derivative
glint analyses that made two incorrect assumptions. The first was to use linear fits to the monopulse
antenna patterns, which is only valid when the target platform is on broadside of the radar. The
second was to assume that the target platform is an infinite distance from the radar, which is not
possible. The analyses also did not consider retrodirectivity. It was only during a later cross-eye
jamming analysis that the limitations were identified and corrected. The limitations in the analysis
could have been identified much sooner if practical measurements were made. The extended cross-eye
jamming analysis made fewer assumptions and was proven accurate by numerous simulations and
some experimental results. However, the only available experiments where the radar rotation was
considered did not implement true retrodirectivity but simulated it by combining isolated channel
measurements. A need was identified for the development of a truly-retrodirective cross-eye jammer in
a laboratory environment to expand the body of knowledge available about cross-eye jamming. The
cost-effective jammer would be used to identify any real-world effects or anomalies that could not be
predicted by the extended analysis or identified by simulation.
This dissertation presents the development of a truly-retrodirective cross-eye jammer by using a
software-defined radio (SDR). The development is accompanied by a method of calibrating the cross-eye
jammer to obtain the ideal magnitude factor and phase difference between the retrodirective paths
by minimising the magnitude of the sum-channel return of a monopulse radar. The developed system
was tested in an anechoic environment against a self-implemented phase-comparison monopulse radar.
It was shown that significant angular errors could be induced. The angular errors were larger than
10° at broadside of the radar. This equated to a minimum miss-distance of around 1 m at a range of
6 m. It was shown that a cross-eye gain of around ten was obtained, which resulted in the indicated
angle of the radar never becoming zero, regardless of the radar rotation. This suggested that tracking
radars, such as that used by active homing missiles, would lose lock on the target platform. Further
experiments also proved the jammer to be retrodirective, with large angular errors for all rotations of
the jammer antennas. All results correlated very well with that predicted by the extended analysis,
with only minor deviations between radar rotations of 0° and 5°. After further investigation, it was
concluded that the deviations were most likely caused by mutual coupling between the radar antennas
and were not caused by a reduction in the performance of the jammer.Electrical, Electronic and Computer EngineeringMEng (Electronic Engineering)Unrestricte
Analysis of path-length effects in multiloop cross-eye jamming
The effect of path-length differences on multiloop retrodirective cross-eye jammers is evaluated. It is shown that such jammers may act as beacons, and the conditions under which this occurs are investigated for two-loop jammers. The sensitivity of the two-loop cross-eye gain to path-length differences is also studied and is found to be small for small path-length differences, but to increase rapidly. The effect of the two-loop cross-eye jammer parameters on path-length effects is also considered.The National Research Foundation of South Africa (NRF) [85845http://ieeexplore.ieee.org/xpl/RecentIssue.jsp?reload=true&punumber=7hj2017Electrical, Electronic and Computer Engineerin
Path-length compensation in multi-loop retrodirective cross-eye jamming
Multiloop retrodirective cross-eye jammers offer the possibility of both simplifying system implementation and improving system performance. However, the signals for each jammer loop propagate along different paths, leading to potentially detrimental effects on system performance. Static and dynamic compensation for path-length differences are introduced and analyzed. Of the two, static compensation is simpler but is only effective for limited engagement geometries. Dynamic compensation is more general but requires an accurate estimate of the engagement geometry.http://ieeexplore.ieee.org/xpl/RecentIssue.jsp?reload=true&punumber=7hj2019Electrical, Electronic and Computer Engineerin
NASA Thesaurus. Volume 2: Access vocabulary
The NASA Thesaurus -- Volume 2, Access Vocabulary -- contains an alphabetical listing of all Thesaurus terms (postable and nonpostable) and permutations of all multiword and pseudo-multiword terms. Also included are Other Words (non-Thesaurus terms) consisting of abbreviations, chemical symbols, etc. The permutations and Other Words provide 'access' to the appropriate postable entries in the Thesaurus
NASA thesaurus. Volume 2: Access vocabulary
The Access Vocabulary, which is essentially a permuted index, provides access to any word or number in authorized postable and nonpostable terms. Additional entries include postable and nonpostable terms, other word entries, and pseudo-multiword terms that are permutations of words that contain words within words. The Access Vocabulary contains 40,738 entries that give increased access to the hierarchies in Volume 1 - Hierarchical Listing
Cumulative index to NASA Tech Briefs, 1970-1975
Tech briefs of technology derived from the research and development activities of the National Aeronautics and Space Administration are presented. Abstracts and indexes of subject, personal author, originating center, and tech brief number for the 1970-1975 tech briefs are presented
NASA thesaurus. Volume 1: Hierarchical Listing
There are over 17,000 postable terms and nearly 4,000 nonpostable terms approved for use in the NASA scientific and technical information system in the Hierarchical Listing of the NASA Thesaurus. The generic structure is presented for many terms. The broader term and narrower term relationships are shown in an indented fashion that illustrates the generic structure better than the more widely used BT and NT listings. Related terms are generously applied, thus enhancing the usefulness of the Hierarchical Listing. Greater access to the Hierarchical Listing may be achieved with the collateral use of Volume 2 - Access Vocabulary and Volume 3 - Definitions
Abstracts on Radio Direction Finding (1899 - 1995)
The files on this record represent the various databases that originally composed the CD-ROM issue of "Abstracts on Radio Direction Finding" database, which is now part of the Dudley Knox Library's Abstracts and Selected Full Text Documents on Radio Direction Finding (1899 - 1995) Collection. (See Calhoun record https://calhoun.nps.edu/handle/10945/57364 for further information on this collection and the bibliography).
Due to issues of technological obsolescence preventing current and future audiences from accessing the bibliography, DKL exported and converted into the three files on this record the various databases contained in the CD-ROM.
The contents of these files are:
1) RDFA_CompleteBibliography_xls.zip [RDFA_CompleteBibliography.xls: Metadata for the complete bibliography, in Excel 97-2003 Workbook format; RDFA_Glossary.xls: Glossary of terms, in Excel 97-2003 Workbookformat; RDFA_Biographies.xls: Biographies of leading figures, in Excel 97-2003 Workbook format];
2) RDFA_CompleteBibliography_csv.zip [RDFA_CompleteBibliography.TXT: Metadata for the complete bibliography, in CSV format; RDFA_Glossary.TXT: Glossary of terms, in CSV format; RDFA_Biographies.TXT: Biographies of leading figures, in CSV format];
3) RDFA_CompleteBibliography.pdf: A human readable display of the bibliographic data, as a means of double-checking any possible deviations due to conversion