Showing papers on "Electromagnetic compatibility published in 1985"

A review of electromagnetic compatibility/interference measurement methodologies

Abstract: This paper presents a review summary of radiated emission and susceptibility measurement methodologies currently used for assessing the electromagnetic compatibility/interference (EMC/EMI) characteristics of electronic devices and systems. In particular, measurement methods using open sites, transverse electromagnetic (TEM) cells, reverberating chambers, and anechoic chambers are discussed, in light of their technical justifications and bases, their strengths and limitations, and interpretation of the measured results.

An Infrared Measurement Technique for the Assessment of Electromagnetic Coupling

Abstract: A non-destructive, non-perturbing infrared measurement technique is under development to observe the effects of electromagnetic coupling of energy to the interior of complicated geometrical structures. The applications, advantages, and disadvantages of this new infrared technology are discussed.

Taming EMI in microprocessor systems: The authors propose a systematic approach to limiting the effects of electromagnetic interference

Abstract: The authors point out that whereas the physics, electronics, and mathematics of EMI-as well as interference caused by electrostatic discharge, a related area-are fairly well documented, problems arise because of the many variables that typically are involved. The difficulty of tracing interfering signals is discussed, and the basic principles of interference are reviewed. The discussion covers the principle sources of radiation from microprocessor-based equipment, the ability of logic gates to function as both sources and receptors of noise, and the radiation emitted from printed circuit boards. Five coupling paths that should be considered in typical systems comprising two or more pieces of equipment are outlined.

Screening measurements in the time domain and their conversion into the frequency domain

Abstract: In the measurement of screening of cables and connectors it is found that a dedicated instrument working in the time domain has many advantages over a swept frequency set-up. Comparison is made using calibration circuits to simulate the screening properties of connectors as well as on genuine cable assemblies.Using the simplest possible relationship between time and frequency domains, quite good agreement can be reached whether the measurement is made on a calibrator or a real connector. The conversion can be used on the homogeneous screen of a semi-rigid cable if care is taken in its application.

Directional scanning of complex electromagnetic environments

Abstract: A directional scanning technique is formulated for determining characteristics of an electromagnetic (EM) environment with a relatively small number of measurements, and results of a simulated application are presented. The method relies on measurements with a directional probe to obtain information about the coefficients in a planewave expansion of the field within a large volume. The simulation indicates that although the spatial variation of the field can not be accurately determined, the spatial average of the field intensity can.

Electromagnetic pulse (EMP) penetration through circular apertures in the frequency domain

Abstract: Equations and curves are given for estimating field coupling from a normally electromagnetic pulse (EMP) incident plane wave through a circular aperture within a thin planar surface.

Basic EMC (Electromagnetic Compatibility) Technology Advancement for C3 Systems. Volume 1B. Demodulation Radio Frequency Interference Effects in Operational Amplifier Circuits.

Abstract: : Since monolithic integrated operational amplifier (op amps) have become important building blocks in today's control and communications systems, a series of investigations have been carried out to determine RFI effects in analog circuits using op amps as active device. The specific RFI effect investigated is demodulations of amplituder-modulated (AM) RF signals in op amp circuits to produce undesired low frequency responses at the AM-modulations frequency. Subsequently, the undesired demodulation responses may be processed in a manner similar to a desired low frequency signal by the low frequency components that follow the order nonlinear transfer function. Keywords include: Electromagnetic compatibility, Electromagnetic interference, Operational amplifiers, Macromodel, Nonlinear response, and Nonlinear transfer function.

A Simple Theory for Predicting the Electromagnetic Performance of Enclosures Using Impedance and Polarizability Measurements

Abstract: The th e o ry o f Madle and H o e f tH l f o r un der ­ s t an d in g th e magnetic f i e l d a t t e n u a t i o n of e n c lo s u re s has been r e f i n e d so t h a t i t can be used t o q u a n t i t a ­ t i v e l y p r e d i c t th e e le c t ro m a g n e t i c performance of e l e c t r i c a l l y small e n c l o s u r e s . Using th e t r a n s f e r impedance of th e j o i n t s , th e s u r f a c e impedance of sh i e ld e d a p e r t u r e s , and th e p o l a r i z a b i l i t y o f a p e r ­ t u r e s , t h i s th e o ry p r e d i c t s th e s u r f a c e magnetic f i e l d a t t e n u a t i o n ( t h e r a t i o o f th e s u r f a c e magnetic f i e l d on th e e x t e r i o r o f th e e n c lo su re t o th e mag­ n e t i c f i e l d i n s id e th e e n c l o s u r e ) . I n t ro d u c t io n The s o l u t i o n of many e l e c t ro m a g n e t i c c o m p a t i b i l ­ i t y problems r e q u i r e s th e a n a l y s i s o r p r e d i c t i o n of t h e e le c t ro m a g n e t i c performance o f s h i e ld e d e n c l o ­ s u r e s . The l i t e r a t u r e does not c o n ta in any s h i e ld i n g a n a l y s i s te c h n iq u e t h a t could be used t o ana lyze the s h i e ld i n g performance o f a wide range of e n c lo s u re s us ing fundamental p h y s i c a l p r i n c i p l e s such as c u r r e n t d i f f u s i o n , a p e r t u r e c o u p l in g , and j o i n t r e s i s t a n c e . This lack o f a c r e d i b l e , v a l id a t e d a n a l y s i s te ch n iq ue i s a major reason f o r e x p e r im e n ta l l y e v a l u a t i n g s p e c i f i c e n c lo su re d e s ig n s on a c a se b y -c a se b a s i s . A c r e d i b l e a n a l y s i s te ch n iq u e would be a tremen­ dous a s s e t t o a s h i e l d i n g des ig n program because i t would a l low th e d e s i g n e r t o choose th o se c o n s t r u c t io n t e ch n iq u es t h a t were a p p r o p r i a t e t o th e s p e c i f i c q u a n t i t a t i v e r e q u i rem en t . He could a l s o i n c o rp o ra t e c o n s t r u c t i o n te c h n iq u e s t h a t o f f e r e d a p o s i t i v e b e n e f i t w i th r e s p e c t t o c o s t and avoid p r a c t i c e s t h a t were d i f f i c u l t o r expensive to manufactu re whi le p rov id in g on ly marg inal improvement. Of p a r t i c u l a r importance was th e use o f g a s k e t s . These a re expen­ s iv e t o i n s t a l l and m a in t a in , and t h e r e i s no q u a n t i ­ t a t i v e method to d e te rm ine i f they a re needed. Along with th e d e s i r e t o have a c r e d i b l e s h i e ld i n g a n a l y s i s t e c h n iq u e , a b e t t e r method f o r s p e c i fy i n g s h i e l d i n g e f f e c t i v e n e s s i s d e s i r e d . The IEEE d e f i n i t i o n of s h i e l d i n g e f f e c t i v e n e s s ( i . e . , the r a t i o o f th e f i e l d a t a p o i n t , w i th and w i th o u t the e n c lo su re ) i s ve ry p r a c t i c a l , bu t i t i s no t based on f i rm p h y s i c a l p r i n c i p l e s s i n c e i t does no t t a k e in to account th e i n t e r a c t i o n / s c a t t e r i n g o f th e f i e l d by th e e n c l o s u r e , and th e d e f i n i t i o n seems in a p p r o p r i a t e when th e e n c lo su re i s p a r t o f a l a r g e r s t r u c t u r e . The su cces s t h a t s u r f a c e t r a n s f e r impedance has en joyed in t h e c a b l e a r e a has r a i s e d hopes t h a t a s i m i l a r i n t r i n s i c p r o p e r ty could be found to be a p p l i c a b l e t o s h i e ld e d e n c l o s u r e s . In f a c t , one could v i s u a l i z e a s u r f a c e t r a n s f e r impedance of an en c lo su re as th e r a t i o o f th e average e l e c t r i c f i e l d a t th e i n s id e s u r f a c e o f th e e n c lo su re t o th e mag­ n e t i c f i e l d a t t h e o u t s i d e s u r f a c e . U n fo r tu n a te ly , measuring th e e l e c t r i c f i e l d on th e i n s id e s u r f a c e i s d i f f i c u l t s i n c e one does n o t have a conven ien t c e n t e r conductor which could "average" th e f i e l d , as in a c a b l e . An in t e r im s o l u t i o n i s t o use s u r f a c e mag­ n e t i c f i e l d a t t e n u a t i o n , d e f in e d in t h i s s tudy as the r a t i o o f th e s u r f a c e magnetic f i e l d on the o u t s i d e of t h e e n c lo su re to t h e magnetic f i e l d i n s id e th e e n c l o ­ su r e . This has v i r t u e in t h a t measurements a re well d e f i n e d , r e s u l t s a re c o n c e p tu a l ly in th e same form as th e r e q u i r e m e n ts , and th e e f f e c t s o f e x t e r n a l co up l ing a r e e l im in a te d from th e s p e c i f i c a t i on /pred i c t i o n . Measurement o f th e s u r f a c e magnet ic f i e l d a t t e n ­ u a t io n of a wide range o f e n c lo su re s 12 ,3 ] have shown t h a t c u r r e n t d i f f u s i o n i s im po r tan t on ly a t low f r e ­ q uen c ies ( l e s s than a few t e n s o f k i l o h e r t z ) o r when t h e e n c lo su re wal l i s very t h i n . P r a c t i c a l examples o f t h e l a t t e r c o n d i t i o n in c lu d e wire mesh f o r f r e ­ q uenc ies below 1 MHz and m e t a l l i c c o a t in g s f o r f r e ­ q uenc ies below se v e ra l t e n s o f MHz. For most e n c lo s u re s made o f metal a t l e a s t 1 mm (0 .040 inch) t h i c k , th e predominant co up l ing mechanism between th e o u t s i d e and in s i d e of th e e n c lo su re i s th e r e s i s t a n c e o f th e j o i n t s and a p e r t u r e c o u p l in g . When e n c lo su re s a re f i l l e d w i th e l e c t r o n i c s , conduc t ive p e n e t r a t i o n s such as th e power and s ig n a l w ir in g may c o n s t i t u t e an o th e r coup l ing mechanism. However, conduc t ive p e n e t r a t i o n s a re g e n e r a l ly not cons id e red t o be p a r t o f th e e n c lo su re and w i l l no t be in c luded in th e t h e o ry p re s e n te d in t h i s s tud y . Thus, th e primary o b j e c t i v e o f a th e o ry f o r p r e ­ d i c t i n g t h e e le c t ro m a g n e t i c performance of an en c lo ­ su re i s t o account f o r p r a c t i c a l im p e r f e c t io n s or d e f e c t s such as a p e r t u r e s and j o i n t r e s i s t a n c e . I t would a l s o be d e s i r a b l e f o r th e th e o ry t o account f o r c u r r e n t d i f f u s i o n so th e performance of conduc t ive e n c lo su re s can be analyzed a t f r e q u e n c ie s where the e f f e c t i v e wall t h i c k n e s s i s l e s s than a sk in dep th . The e le c t ro m a g n e t i c a n a l y s i s o f e n c lo s u re s can be s i m p l i f i e d by on ly c o n s id e r in g s i t u a t i o n s where th e e n c lo su re i s e l e c t r i c a l l y sm a l l . For th e se c a s e s , t h e r e i s no s i g n i f i c a n t phase d i f f e r e n c e between f i e l d s , c u r r e n t s , and v o l t a g e s a t d i f f e r e n t p o in t s on th e e n c l o s u r e ; and th e a n a l y s i s can be c a r r i e d ou t us ing lumped p a ram e te r s . Using t h i s s i m p l i f i c a t i o n does n o t impose a s e r io u s l i m i t a t i o n on th e a n a l y s i s s i n c e most e n c l o s u r e s , in c lu d in g r a c k s , a re l e s s tha n a few mete rs in s i z e and t h e r e f o r e a re e l e c t r i c a l l y small f o r f r e q u e n c ie s below about a hundred megaher tz . Equipment boxes a re s m a l l e r ; t h e r e f o r e th e s i m p l i f i c a t i o n does not i n t r o ­ duce s e r io u s u n c e r t a i n t i e s u n t i l h ig h e r f r e q u e n c ie s a r e reached . The p r e s e n t s tudy i s concerned with p r e d i c t i n g th e e le c t ro m a g n e t i c performance of e n c lo s u re s when th e source i s o u t s i d e . The th e o ry could be extended to c a se s where th e source i s in s id e th e e n c l o s u re , but t h i s e x t e n s io n would r e q u i r e assumptions conce rn ­ ing th e boundary c o n d i t i o n o u t s id e th e e n c lo su re and t h e i n t r o d u c t io n o f c on cep t s such as s l o t an ten n as , e t c . , t o account f o r a l l t h e ph ys ica l p r i n c i p l e s . Note t h a t th e magnetic f i e l d a t t e n u a t i o n i s g e n e r a l ly no t th e same in both d i r e c t i o n s . In th e 1950s, Quine!4 ! developed some in n o v a t iv e te c h n iq u e s f o r per forming p r a c t i c a l a n a l y s i s of e n c l o s u r e s , e s p e c i a l l y when th e source was i n s i d e . In 1981, CaseyiS] t h e o r e t i c a l l y i n v e s t i g a t e d a p e r ­ t u r e s covered wi th cond uc t ive f i lm s and wire mesh. Among o th e r t h i n g s , he in t ro du ced th e ide a of an e f f e c t i v e magnet ic p o l a r i z a b i l i t y o f a d i s t r i b u t e d

Rusty Bolt EMC Specification Based on Nonlinear System Identification

Abstract: There is a recognized interference problem in dense electronic platforms due to harmonic and inter-modula­ tion interference caused by the nonlinearity of metalinsulator-metal (MIM) or metal-oxide-metal (MOM) junc­ tions in the coupling paths between collocated trans­ mitters and receivers. Although the surfaces involved can be distributed in nature, the junction is colloqui­ ally called the "rusty bolt". This paper examines the identification of the lumped parameter rusty bolt non­ linear transfer functions (NLTFs) and their use in pre­ dicting electromagnetic compatibility (EMC) specifica­ tion parameters such as intermodulation and harmonic distortion. Results illustrating the procedure are presented. The errors which can be encountered in the identified parameters and in the predicted EMC speci­ fication parameters are examined. It is concluded that the EMC parameters up to the fifth order can be predicted with good quality provided that the number of poles is identified correctly and that the identification errors are reasonable (say less than 30 percent).

Electromagnetic Compatibility Testing of Spread Spectrum Communication Systems

Abstract: This paper addresses altering electromagnetic emission and susceptibility testing methods for adaptation to frequency hopped spread spectrum communication systems. A discussion of the nature of the interference introduces the subject. Various problems associated with emission and susceptibility testing techniques when applied to. frequency hopped systems are discussed. Expansion of normal defini­ tions and methods associated with electromagnetic compatibility testing are indicated.

Electro-impulse de-icing research: fatigue and electromagnetic interference tests

Abstract: : Electro-Impulse De-Icing (EIDI) has been recently developed and tested with very encouraging results. Questions remain, however, regarding the fatigue life and electromagnetic compatibility of the system. Fatigue tests were conducted on two production aluminum wing leading edges and one composite material leading edge. These were done at realistic temperatures and impulse energies for an estimated aircraft lifetime of ice protection. Coil mounting brackets were the main casualties. Wing components did not fail. Tests were also conducted for metal and composite wings of electromagnetic radiation of EIDI over a wide frequency range. The aluminum wing was found to be an excellent shield. All wires external to the aluminum wing were shown to require careful shielding. The composite wing required all wiring and the metal doublers to be shielded and grounded.

VHF Radio Noise Measurements Near a Roadway Carrying 10 000 Vehicles per Hour

Abstract: Measurements of noise power spectral density were recorded with a vertical monopole at 47 MHZ, about 0.5 km from Interstate Highway I-95 (Massachusetts Route 128), in Waltham, Massachusetts, which was carrying traffic approaching 10 000 vehicles per hour. Average noise power values were found to be in excellent agreement with predictions based on vehicle density reported by Spaulding in 1972.

Electromagnetic Compatibility: Sources and levels of disturbances in the telecommunications environment

Abstract: The electromagnetic environment in which telecommunications equipment has to operate may vary from favourable to very hostile, partly by reason of ambient conditions and partly because a considerable range and volume of disturbance is generated by the equipment itself. This Paper provides an overall review of the environment in both Administration and customer occupied buildings. It examines the controls and regulations currently existing and under discussion and studies the effects of hostile conditions upon the equipment. Some real-life cases will be described to demonstrate the points made and give engineers who may be unfamiliar with the subject an insight into its practicalities. Finally, the work of the IEC International Special Committee on Radio Interference (CISPR) and that of the Conference of European Posts and Telecommunications (CEPT) in the field of Electromagnetic Compatibility as it applies to telecommunications will be reviewed.

Accuracy Estimation in Anechoic Chamber Testing

Abstract: T h e a s s u m p t i o n t h a t a m i s s i l e ' s operational electromagnetic environment can be a c c u r a t e l y s i m u l a t e d in an RF a n e c h o i c c h a m b e r b r i n g s c e r t a i n e r r o r s i n t o e l e c t r o m a g n e t i c c o m p a t i b i l i t y testing. A c h i e f s o u r c e of e r r o r is the d i f f e r e n c e b e t w e e n the p l a n e w a v e i l l u m i n a t i o n of an operational environment and the illumination of a d i r e c t i v e t e s t antenna. A m e t h o d o f m o m e n t s t e c h n i q u e e s t i m a t e s the s u r f a c e currents on a missile when illuminated by a p l a n e w a v e a n d b y t w o s i m p l e a n t e n n a s . T h e s e c u r r e n t s a r e c o m p a r e d to m e a s u r e the c o r r e s p o n d e n c e of the test and o p e r a t i o n a l e n v i r o n m e n t s . S i m p l e g u i d e l i n e s a r e d e v e l o p e d w h i c h a l l o w t est e n g i n e e r s to e s t i m a t e and m i n i m i z e this s o u r c e of e r r o r in RF anechoic chamber testing.

An Overview of the Intrasystem EMC Analysis Program with Graphics

Abstract: It is well known that as computer programs become more complex, the user interface must be simplified to enhance the data interpretation. This paper will provide a brief overview of the Intrasystem Electromagnetic Compatibility Analysis Program called IEMCAP, and the improvements made by Kaman Sciences Corporation (KSC) to streamline the basic IEMCAP output. The composite electromagnetic compatibility (EMC) code will be referred to as the Intrasystem Electromagnetic Compatibility Analysis Program with Graphics (IEMCAP-G). The basic IEMCAP code and its output will be introduced, followed by a discussion of the improvements made to the IEMCAP output. The improvements include: output matrices, extraction of data, antenna position graphics, and line plots. These modifications aid the EMC engineer in determining potential electromagnetic interference (EMI) problems and their solutions.

Comparison of Failure Mode Criteria in Electromagnetic Environments

Abstract: Open field/ground plane test methods are generally used to evaluate the performance of equipment in electromagnetic environments. Laboratory enclosures with controlled environments in the form of transverse electromagnetic (TEM) cells, reverberation chambers, and anechoic chambers can overcome the disadvantages of remote outdoor test facilities.

Methodology for Determination of Circuit Safety Margins for MIL-E-6051 EMC System Test

Abstract: A MIL-E-6051 electromagnetic co m patib il ity (EMC) te s t includes the establishment of safety margins fo r selected mission c r i t i c a l c irc u its fo r v e r i f ic a t io n o f system co m p atib il ity . Those c irc u its with the lowest safety margins are instrumented fo r tes t in g . A method has been developed fo r the determination of safety margins fo r mission c r i t i c a l c irc u its of the B-1B Avionics and across the e le c tr ic a l interfaces with a l l elements of the B-1B subsystems. The electromagnetic energy coupled between c irc u its and c i r c u i t threshold levels are required fo r determining the safety margins. A coupling analysis computer program, t i t l e d Intrasystem Electromagnetic Com patib ility Analysis Program (IEMCAP) and supplied by the Rome A ir Development Center, was u t i l i z e d to predict the w ire -to -w ire coupling by deta iled modeling of the B-1B. The method of deriving c i r c u i t source and load resistances and threshold level fo r a typ ica l d i f fe re n t ia l l in e d r ive r and receiver c i r c u i t w i l l be demonstrated. The techniques developed fo r analyzing the B-1B Avionics would be useful in determining c i r c u i t safety margins fo r use as c r i t e r ia in selecting c irc u its fo r instrumentation and tes ting fo r other electron ic systems.

The Transient State of Arbitrarily Shaped Microstrip Antennas

Abstract: Using the specific methods of transient electromagnetic field some new aspects of microstrip antennas are discussed. The transient response, the input impedance, the realizability and the possibility of an equivalent circuit of these antennas are presented.

The revision of EMC specifications for military aircraft equipment.

Abstract: This thesis evaluates standard EMC aircraft equipment specifications highlighting their weaknesses and suggesting modifications, some of which have already been included in the new generation of specifications now being introduced. The relationship of the equipment level EMC test to the whole aircraft EMC test is discussed and improvements to this latter activity, which have been developed as a result of the work programme described in this thesis, are presented and evaluated.

Radiated-Emission Ramifications of Multiple IC Sourcing

Abstract: An unaccep tab le increase in the rad ia ted emissions am plitudes of an e lectron ic d a ta processing product was a ttr ib u ted to m ultiple in teg ra ted -c ircu it (IC) sourcing. Conducted w aveform s genera ted by these devices on the data /add ress bus w ere m easured in the tim e domain. Emissions rad ia ted from various IC sources w ere m easured in the frequency domain a t an open-field te s t site . Interchanging ICs, even though of a sam e device type, had a significant im pact upon th e EMC profile.