Showing papers on "Electromagnetic compatibility published in 1978"

Electromagnetic Susceptibility Measurements Using a Mode-Stirred Chamber

Abstract: Within the electromagnetic compatibility community it is recognized that there is a need for better methods to measure the radiat1 2 3 ed susceptibility of electronic systems. ' ' Free-space measurement facilities are economi­ cally unattractive, and the usual recourse is to conduct susceptibility tests within shielded rooms. Shielded room data are not, however, solely indicative of the test specimen characteristics; such data are influenced by room characteristics such as size, shape, and loss as well as location of the specimen and associated test equip­ ment within the room. It is easy, however, to convert any standard shielded room into a "mode-stirred" chamber wherein radiated susceptibility tests can be performed with results that are accurate, repeatable, and independent of test set-up. The problem of relating free-space and mode-stirred environ­ ments is approached in two ways, with the end result being a calibration graph that relates chamber input power to equivalent plane wave power density inside the chamber. The accuracy of mode-stirred chamber data is demonstrated by comparing susceptibility profiles from both free-space and modestirred test environments.

Field measurements made in an enclosure

Abstract: This paper presents a survey of radiated emission and susceptibility measurement methods which can be employed to evaluate the electromagnetic interference (EMI) characteristics of electronic systems. The paper reviews conventional anechoic-chamber and shieldedenclosure-measurement methods, as well as alternate methods which have been developed to circumvent measurement problems associated with radiated measurements in conventional shielded enclosures. Alternative methods presented include hooded antennas, mode perturbation, statistical sampling transverse electromagnetic (TEM) cells, and other techniques such as parallel-plates low-Q-enclosures, and long-wire-antennas. A qualitative comparison of each technique in terms of advantages and limitations is also given.

Electromagnetic Properties and Effects of Advanced Composite Materials: Measurement and Modeling

Abstract: : This report covers several areas: (1) Electromagnetic properties of composite materials are given for the range DC to 30 MHZ; (2) Techniques of measurement are discussed in the range DC to 1 GHz; (3) Electromagnetic shielding theory is discussed; Surface transfer impedance and the two loop method are related to the conductivity. A matrix method for the calculation of shielding effectiveness for laminated anisotropic materials (perpendicular incidence) is presented; (4) The modification required by the method of moments to allow calculation involving non-perfect conductors are discussed; and (5) A comparison of antenna patterns over a graphite/epoxy ground plane and an aluminum ground plane for dipole and monopole antennas at 370 MHz and 837 MHz is given.

A digital low frequency spectrum analyzer, using a programmable pocket calculator

Abstract: A measuring instrument utilising the Texas Instruments' appliances SR 52 or SR 56 is described. An application as a dig~tal noise measuring system is discussed in detail. The same instrument can, however, perform other functions. Results concerning sine-wave and noisy input signals are presented. The instrument makes use of an input-output processor for the SR 52/56, developed by verkroost [lJ, for which the author designed and tested print lay-outs.

A Mathematical Analysis of the Electromagnetic Compatibility of Twisted Wires

Abstract: In this paper the electromagnetic compatibility of twisted wires is evaluated. A twisted pair is uniquely represented by arrays of loops and dipoles. For many practical applications, the circum­ ference of the loop is small compared to the wavelength of in ter­ ference. When such is the case, only the transmission mode of pro­ pagation and normal mode of radiation are of interest, as the ax­ ial mode of radiation is very small compared to the normal mode of radiation. Mathematical formulas of power received by arrays for both uniform and non-uniform excitation are compared with the power received by a two-wire line of the same length as the a r­ ray. The relative shielding effectiveness of a twisted-pair cable with respect to a two-wire line is calculated from their power ratio.

Applications of Multiconductor Transmission Line Theory to the Prediction of Cable Coupling. Volume 6. A Digital Computer Program for Determining Terminal Currents Induced in a Multiconductor Transmission Line by an Incident Electromagnetic Field

Abstract: : The report describes a digital computer program which is designed to compute the terminal currents induced in a multiconductor transmission line by an incident electromagnetic field Sinusoidal steady state behavior of the line is assumed The transmission line is uniform and consists of n wires and a reference conductor immersed in a homogeneous, lossless, linear, isotropic medium The n wires and the reference conductor are assumed to be lossless The reference conductor may be a wire, an infinite ground plane or an overall, cylindrical shield The incident electromagnetic field may be a uniform plane wave or a general nonuniform field The primary restriction on the program validity is that the cross sectional dimensions of the line, eg, wire separation, must be much less than a wavelength

Validation of IEMCAP using the B-52

Abstract: This study a s s e s s e d the e f f e c t i v e n e s s o f th e I n tr a ­ system E lec trom agn etic C o m p a t ib il i ty A n a ly s is Program (IEMCAP) i n p r e d ic t in g antenn a-cou p led in t e r f e r e n c e problem s. The B-52 a i r c r a f t i s used i n th e c a se s tu d y . The study co n c lu d es th a t IEMCAP does c o r r e c t l y p r e d ic t a h ig h p ercen ta g e o f a c t u a l in t e r f e r e n c e problem s.

PECAL: A New Computer Program for the EMC Performance Evaluation of Communication Systems in a Cosite Configuration

Abstract: A computer program (PECAL) is described which pre­ dicts the performance of multiple EM communication equipments in the 2 to 400 MHz band when placed in a Navy shipboard (single-ship) configuration. A com­ bination of linear and nonlinear interference phenom­ ena are analyzed. The scope of the program is limited to the treatment of interference mechanisms involving radiated, antenna coupled signals and multicoupler crosstalk signals. The EMC performance measures are expressed in terms of statistics, as are many of the model parameters used in the interference prediction equations.

Diagnosis and cure of some EMC and interference immunity problems

Abstract: Several recent interference investigations are described in some detail. They demonstrate that the technique of injection of radio frequency currents into the earth is effective in locating the weak points in system screens. The use of suitable cables, connectors, filters and remedial techniques can transform what appears to be in some cases a useless system into a trouble-free one. The use of a specially developed pulse generator is shown to be particularly effective when investigating problems in digital systems.

Railroad electromagnetic compatibility. volume ii. assessment for classification yards and electrification

Abstract: The automated freight classification yard electromagnetic environment is composed of electrical and electronic devices that are each potential sources and/or victims of electrical interference. The electromagnetic radiation of the environment and selected railroad yard devices such as doppler radars and switch machines was measured at three railroad classification yards. The susceptibilities of selected yard devices were measured to determine operational sensitivity to the yard electromagnetic radiations. In addition to yards, since railroad electrification has important implications, radiations from an electrified railroad operating at 50 kilovolt 60 Hertz were also measured to formulate a measurement methodology and to determine the potential interference effects on railroad operations.

An Underwater Towed Electromagnetic Source for Geophysical Exploration

Abstract: Low frequency electromagnetic methods are used in geophysical exploration by detecting the magnetic field distortion between a transmitter and receiver produced by locally conductive bodies. Both ground and airborne systems are in current use. One airborne multi-coil aerial electromagnetic prospecting system houses the transmitter and receiver in a 30 ft bird while another reduces the system to an impedance measurement using a single super-conducting coil. It is possible to extend low frequency airborne geologic prospecting techniques into the ocean environment by employing an underwater towed source of electromagnetic radiation and a receiving magnetic or electric field detector. The receiver can be simultaneously towed on an auxiliary cable, boom mounted on the towing platform (surface or subsurface), or land or underwater based.

Factors in an EM Methodology

Abstract: Weapon system complexity and cost saving concepts are forcing changes in management and engineering methods for solving EM problems. Methodologies for use in weapon system acquisition are currently in the evolutionary stage of development within the EM commu­ nity. To cope with the changes, systematic and logical procedures are needed to define common goals, to commu­ nicate within large orgainzational structures, and to ensure good planning. Five factors for inclusion in an EM methodology are identified and discussed.

Some Aspects of Valid EMC Testing of Missiles

Abstract: Integral-equation and numerical techniques are used to determine guidelines in valid electromagnetic compatibility (EMC) testing of missiles. Both thin-wire and body-of-revolution modeling are used. Investigated are two primary aspects. 1) If a near-zone source is used rather than plane-wave incidence, how far must the source be for valid simulation, and 2) how significant is the presence of the rocket exhaust (or plume) in determining subsystem response, and need it be included for valid EMC testing? The simulation validity conclusions reached for the models without apertures apply directly as well to the real-life body with apertures. Numerical results are given over the frequency range of 50-200 MHz to help establish guidelines on testing validity.

New Probes for Electromagnetic Fields

Abstract: A new method is described enabling us to detect electromagnetic fields and define them. A miniaturized antenna electrically isolated in space is used therefore introducing only a minimal perturbation of a measured quantity.