45 research outputs found
A Method against Interrupted-Sampling Repeater Jamming Based on Energy Function Detection and Band-Pass Filtering
Interrupted-sampling repeater jamming (ISRJ) is a new kind of coherent jamming to the large time-bandwidth linear frequency modulation (LFM) signal. Many jamming modes, such as lifelike multiple false targets and dense false targets, can be made through setting up different parameters. According to the “storage-repeater-storage-repeater” characteristics of the ISRJ and the differences in the time-frequency-energy domain between the ISRJ signal and the target echo signal, one new method based on the energy function detection and band-pass filtering is proposed to suppress the ISRJ. The methods mainly consist of two parts: extracting the signal segments without ISRJ and constructing band-pass filtering function with low sidelobe. The simulation results show that the method is effective in the ISRJ with different parameters
Quasi-Coherent Noise Jamming to LFM Radar Based on Pseudo-random Sequence Phase-modulation
A novel quasi-coherent noise jamming method is proposed against linear frequency modulation (LFM) signal and pulse compression radar. Based on the structure of digital radio frequency memory (DRFM), the jamming signal is acquired by the pseudo-random sequence phase-modulation of sampled radar signal. The characteristic of jamming signal in time domain and frequency domain is analyzed in detail. Results of ambiguity function indicate that the blanket jamming effect along the range direction will be formed when jamming signal passes through the matched filter. By flexible controlling the parameters of interrupted-sampling pulse and pseudo-random sequence, different covering distances and jamming effects will be achieved. When the jamming power is equivalent, this jamming obtains higher process gain compared with non-coherent jamming. The jamming signal enhances the detection threshold and the real target avoids being detected. Simulation results and circuit engineering implementation validate that the jamming signal covers real target effectively
Waveform-Domain Adaptive Matched Filtering: A Novel Approach to Suppressing Interrupted-Sampling Repeater Jamming
The inadequate adaptability to flexible interference scenarios remains an
unresolved challenge in the majority of techniques utilized for mitigating
interrupted-sampling repeater jamming (ISRJ). Matched filtering system based
methods is desirable to incorporate anti-ISRJ measures based on prior ISRJ
modeling, either preceding or succeeding the matched filtering. Due to the
partial matching nature of ISRJ, its characteristics are revealed during the
process of matched filtering. Therefore, this paper introduces an extended
domain called the waveform domain within the matched filtering process. On this
domain, a novel matched filtering model, known as the waveform-domain adaptive
matched filtering (WD-AMF), is established to tackle the problem of ISRJ
suppression without relying on a pre-existing ISRJ model. The output of the
WD-AMF encompasses an adaptive filtering term and a compensation term. The
adaptive filtering term encompasses the adaptive integration outcomes in the
waveform domain, which are determined by an adaptive weighted function. This
function, akin to a collection of bandpass filters, decomposes the integrated
function into multiple components, some of which contain interference while
others do not. The compensation term adheres to an integrated guideline for
discerning the presence of signal components or noise within the integrated
function. The integration results are then concatenated to reconstruct a
compensated matched filter signal output. Simulations are conducted to showcase
the exceptional capability of the proposed method in suppressing ISRJ in
diverse interference scenarios, even in the absence of a pre-existing ISRJ
model
Radar Range Deception with Time-Modulated Scatterers
Modern radar systems are designed to have high Doppler tolerance to detect
fast-moving targets. This means range and Doppler estimations are inevitably
coupled, opening pathways to concealing objects by imprinting artificial
Doppler signatures on the reflected echoes. Proper temporal control of the
backscattered phase can cause the investigating radar to estimate wrong range
and velocity, thus cloaking the real position and trajectory of the scatterer.
This deception method is exploited here theoretically for arbitrary Doppler
tolerant waveforms and then tested experimentally on an example of the linear
frequency modulated radar, which is the most common waveform of that class used
in practice. The method allows retaining radio silence with a semi passive
(battery assisted) approach that can work well with time-dependent
metasurfaces. Furthermore, as an insight into new capabilities, we demonstrate
that temporally concealed objects could even be made to appear closer than they
truly are without violating the laws of relativity
Jamming Cognitive Radios
The goal of this thesis is to identify and evaluate weaknesses in the rendezvous process for Cognitive Radio Networks (CRNs) in the presence of a Cognitive Jammer (CJ). Jamming strategies are suggested and tested for effectiveness. Methods for safe- guarding the Cognitive Radios (CRs) against a CJ are also explored. A simulation is constructed to set up a scenario of two CRs interacting with a CJ. Analysis of the simulation is conducted primarily at the waveform level. A hardware setup is constructed to analyze the system in the physical layer, verify the interactions from the simulation, and test in a low signal-to-interference and noise ratio (SINR) environment. The hardware used in this thesis is the Wireless Open-Access Research Platform. Performance metrics from open literature and independent testing are compared against those captured from the jamming tests. The goal of testing is to evaluate and quantify the ability to delay the rendezvous process of a CRN. There was some success in delaying rendezvous, even in a high SINR environment. Jamming strategies include a jammer that repeats an observed channel-hopping pattern, a jammer with random inputs using the same algorithm of the CRs, a jammer that estimates channel-hopping parameters based on observations, and a random channel-hopping jammer. Results were compared against control scenarios, consisting of no jamming and a jammer that is always jamming on the same channel as one of the CRs. The repeater, random inputs to the CR algorithm, observation-based estimation jammer, and the random channel hopping jammer were mildly successful in delaying rendezvous at about 0%, 9%, 0%, and 1%, respectively. The jammer that is always on the same channel as a CR had an overall rendezvous delay about 13% of the time
NASA compendium of satellite communications programs
A comprehensive review is given of worldwide satellite communication programs that range in time from the inception of satellite communications to mid-1974. Particular emphasis is placed on program results, including experiments conducted, communications system operational performance, and technology employed. The background for understanding these results is established through brief summaries of the program organization, system configuration, and satellite and ground terminal characteristics. Major consideration is given to the communications system aspects of each program, but general spacecraft technology and other experiments conducted as part of the same program are mentioned summarily
TDRSS telecommunications study. Phase 1: Final report
A parametric analysis of the telecommunications support capability of the Tracking and Data Relay Satellite System (TDRSS) was performed. Emphasis was placed on maximizing support capability provided to the user while minimizing impact on the user spacecraft. This study evaluates the present TDRSS configuration as presented in the TDRSS Definition Phase Study Report, December 1973 to determine potential changes for improving the overall performance. In addition, it provides specifications of the user transponder equipment to be used in the TDRSS
Study of modulation techniques for multiple access satellite communications
Multiple access communication utilizing small ground stations for satellite communication modulation - multiplexing technique
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