28,403 research outputs found
An overview of electromagnetic interference problems in spacecraft
Electromagnetic Interference Workshop held at JPL /Feb., 1968/ permitted an exchange of information on electromagnetic interference problems encountered in aerospace programs. The experiences related at this workshop dealt primarily with Surveyor, Lunar Orbiter, OGO, ATS, and Mariner unmanned programs
Space shuttle lightning protection criteria document
The lightning environment for design is defined and imposes the requirements that the design must satisfy to insure the protection of the space shuttle vehicle system from the direct and indirect effects of lightning. Specifications, criteria, and guidelines provide a practical and logical approach to the protection problems. Protection against the indirect effects of lightning is intimately involved with the electromagnetic compatibility and electromagnetic interference functions. While this document does not deal specifically with electromagnetic compatibility and electromagnetic interference, it does deal with the interactions between lightning protection measures and measures employed for electromagnetic compatibility and control of electromagnetic interference
Assessment and control of spacecraft electromagnetic interference
Design criteria are presented to provide guidance in assessing electromagnetic interference from onboard sources and establishing requisite control in spacecraft design, development, and testing. A comprehensive state-of-the-art review is given which covers flight experience, sources and transmission of electromagnetic interference, susceptible equipment, design procedure, control techniques, and test methods
Electromagnetic interference aspects of integrating a UHF/VHF receiver onboard Mariner 5
Electromagnetic interference assessment in integration of Mariner 5 UHF/VHF receive
Distributed Nonparametric Sequential Spectrum Sensing under Electromagnetic Interference
A nonparametric distributed sequential algorithm for quick detection of
spectral holes in a Cognitive Radio set up is proposed. Two or more local nodes
make decisions and inform the fusion centre (FC) over a reporting Multiple
Access Channel (MAC), which then makes the final decision. The local nodes use
energy detection and the FC uses mean detection in the presence of fading,
heavy-tailed electromagnetic interference (EMI) and outliers. The statistics of
the primary signal, channel gain or the EMI is not known. Different
nonparametric sequential algorithms are compared to choose appropriate
algorithms to be used at the local nodes and the FC. Modification of a recently
developed random walk test is selected for the local nodes for energy detection
as well as at the fusion centre for mean detection. It is shown via simulations
and analysis that the nonparametric distributed algorithm developed performs
well in the presence of fading, EMI and is robust to outliers. The algorithm is
iterative in nature making the computation and storage requirements minimal.Comment: 8 pages; 6 figures; Version 2 has the proofs for the theorems.
Version 3 contains a new section on approximation analysi
Polypyrrole Coated PET Fabrics for Thermal Applications
Polypyrrole can be chemically synthesized on PET fabrics, giving rise to textiles with high electric conductivity. These textiles are suitable for several applications from antistatic films to electromagnetic interference shielding devices. Here we discuss the thermal-electric performance and the heat generation of polypyrrole coated PET fabric samples, previously studied because of their electric conductivity and electromagnetic interference shielding effectiveness. The measured Seebeck effect is comparable with that of metallic thermocouples. Since polypyrrole shows extremely low thermal diffusivities regardless of the electrical conductivity, the low thermal conductivity gives significant advantage to the thermoelectric figure-of-merit ZT, comparable with that of some traditional inorganic thermoelectric materials. The heat generation is also investigated for possible heating textile devices. The results confirm polypyrrole as a prom- ising material for thermal electric applications due to its easy preparation in low cost processin
Probes for measuring noise current in an electronic cable
Electromagnetic interference in deep-space network receiver is often caused by stray coupling from power lines. These stray signals create potential differences between ground terminals, which leads to excessive noise in receiver circuits. Pair of probes detect and measure noise currents in conductors
Photovoltaic system test facility electromagnetic interference measurements
Field strength measurements on a single row of panels indicates that the operational mode of the array as configured presents no radiated EMI problems. Only one relatively significant frequency band near 200 kHz showed any degree of intensity (9 muV/m including a background level of 5 muV/m). The level was measured very near the array (at 20 ft distance) while Federal Communications Commission (FCC) regulations limit spurious emissions to 15 muV/m at 1,000 ft. No field strength readings could be obtained even at 35 ft distant
EMI suppression in heat sinks
Heat sinks are designed to dissipate heat; however, their shapes often lend themselves to radiating electromagnetic energy, which leads to unwanted electromagnetic interference (EMI). This disclosure describes heat sinks that minimize electromagnetic interference at particular design frequencies
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