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Table of Contents
IEEE Electromagnetic Compatibility Group
Computer Determination of Electromagnetic Wave Shielding Effectiveness
The author has developed a technique for rapid determination of the shielding effectiveness of any metal through use of the IBM remote access computing system (RAX). RAX consists of one central computer and numerous control terminals placed throughout Bell Aerosystems engineering areas. To obtain a matrix of shielding information versus frequency the engineer activates his terminal, inserts his program from the library file, and supplies the desired metal thickness, conductivity, permeability, and test distance. The terminal then prints a table of shielding effectiveness. The entire process can be accomplished in about four minutes. This paper includes several samples of output data, lists the program which was used, and shows how the engineer communicates with the machine to obtain the desired output.
Factors Affecting the Measured Value of Impulse Bandwidth
The errors introduced in the measured value of impulse bandwidth obtained by determining the area under the response curve are discussed. The required pulse width of a narrow pulse used to stimulate the impulse response of a linear network is also analyzed. The results are presented in terms of the integral-square error between the true impulse response and simulated response as a function of band-width-pulse-width product. The trapezoidal method of numerical integration as applied to this measurement is briefly discussed.
Electrostatic Potential Generated by Rockets on Vehicles in Space
Investigators have reported the existence of electric current in the exhaust plumes of rocket engines and have speculated that this current could generate a sufficiently high electrostatic potential on vehicles in space to interfere with or damage electronic subsystems or instrumentation. This paper identifies the source of the observed current, calculates its magnitude as a function of the engine parameters, and demonstrates that the rocket plume itself can discharge a vehicle in space and prevent buildup of dangerous potentials.
Performance of Electrically Small Array Receiving Systems in the Presence of Noise
The performance of broad band electrically small beamed receiving arrays operating in the high-frequency band (3 to 30 MHz) and in a random noise environment is studied. The concepts of system noise figure (SNF) and signal-to-noise ratio improvement factor (SNIF) are proposed as criteria for comparing one array antenna receiving system to any reference antenna system when the conditions of operation are defined. Graphical representations of SNIF for the two- and four-element antenna systems versus a single-element system are presented. SNIF is shown to depend on the geometry of the array, on the phasing network, and on the ratio of atmospheric noise power to internal system noise power.
Diode Mixer Coefficients for Spurious Response Prediction
The precise prediction of spurious response levels in a superheterodyne receiver would greatly aid the receiver designer besides being necessary for the representation of a radio frequency interference environment. The power series is used to represent the nonlinear receiver mixer in order to obtain an expression for the receiver spurious response sensitivity. This sensitivity expression contains the power series coefficients and shows that the coefficient magnitudes must be known before the spurious response levels can be computed. Therefore, a method is developed to provide a solution for the power series coefficients of a typical mixer circuit configuration. In the analysis to determine the coefficients, the input voltage-output current loop equation is written for a crystal mixer equivalent circuit. This expression is expanded in a power series and then the reversion of a series technique is implemented to obtain the desired output-input expression in series form. The effects of the nonlinear element (diode) and the total circuit resistance are included in the results. Coefficient expressions are determined up to the ninth order in the manner described above and the level of each expression is computed versus the product ¿( IR + Iÿ) RT where ¿ and IR are diode parameters, RT is the equivalent circuit resistance, and Iÿ, is the dc bias current. Also, the effect of diode bias upon spurious response sensitivity is considered and the results are plotted. The results show the mixer dc operating conditions which must exist in order to reduce spurious response sensitivity.
Lossy Transmission Line Filters
Reactive bandpass and low-pass filters often exhibit spurious responses in the frequency region above the design passband. The spurious responses limit the effectiveness of the filter in preventing interference by out-of-band signals. A simple and inexpensive technique for reducing or eliminating these passbands is to add short sections of an appropriate lossy transmission line in series with the conventional filter. A significant size reduction of conventional transmission line reactive filters can also be realized along with the reduction or elimination of spurious passbands by combining a lossy dielectric with the conventional reactive elements. This paper discusses the application of lossy line filters in cascade with and integrated into conventional reactive filters. The design of lossy transmission line sections and wide-band impedance matching techniques are described.
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Measured and Calculated Spectral Amplitude Distribution of Lightning Sferics
A study was performed to predict the average level of spectral amplitude distribution of sferics over the frequency range from 1 kHz to 10 GHz. The effort includes the compilation and analysis of available sferic measurements. Since no reliable data were available in the literature for frequencies above 1 GHz, a theoretical analysis of lightning streamers was conducted to predict the spectral distribution up to 10 GHz.
Designing Microwave Mixers for Increased Dynamic Range
The principal factors limiting dynamic range in microwave frequency mixers are reviewed, and recently developed methods of extending the dynamic range are summarized. The principles are shown to be applicable to a wide variety of nonlinear elements at all frequency ranges up to and including the microwave range. Specially developed equipment for measuring mixer performace is described, and typical experimental results given. The significance of the suggested techniques to communications and video systems is demonstrated.
Electromagnetic Pulse Transmission Through a Thin Sheet of Saturable Ferromagnetic Material of Infinite Surface Area
A numerical solution is presented for determining the shielding properties of a thin sheet of saturable ferromagnetic material of infinite surface area. Several examples are given to indicate the behavior of ferromagnetic shields in an intense electromagnetic environment. These examples illustrate that only a few numerical results are required to determine the electric field transmitted through the material for a given incident pulse of any amplitude.
The Response of a Terminated Two-Wire Line Buried in the Earth and Excited by a Plane-Wave RE Field Generated in Free Space
A terminated two-wire transmission line is buried at constant depth near the earth-air interface with one conductor directly below the other. A plane-wave electromagnetic field, generated in free space, impinges upon the boundary where it undergoes partial reflection and transmission. The field transmitted into the earth excites the transmission line. The polarization of the electric field is chosen such that the field is directed parallel to the line conductors. The interaction of the line with the dispersive medium and the line losses are considered. The objective of the study is to determine the current in specified load impedances in terms of the amplitude of the incident electric field evaluated at the surface of the earth.
The Response of a Terminated Two-Wire Line Suspended in Air Above a Semi-Infinite Dissipative Medium and Excited by a Plane-Wave RF Field Generated in Free Space
The analysis previously made to determine the response of a two-wire transmission line buried at constant depth near the earth-air interface when excited by a plane-wave electromagnetic field generated in free space is extended to include the case of the line suspended in air at a uniform distance above the earth's surface. The exciting field is the vector sum of the incident and reflected fields at the point midway between the line conductors. The polarization of the electric field is taken to be parallel to the wires, so that there is no pick up by the terminations. The objective of the study is to determine bounds for the current in specified load impedances in terms of the amplitude of the incident electric field evaluated at the surface of the earth.
Electric Field Propagation in the Proximal Region
A model for electric field propagation above planeearth in the region from 1 meter to 10 km from the source, specifically tailored to permit rapid quantitative solutions of EMI (electromagnetic interference) propagation problems, is obtained from classical ground-wave propagation theory extended to include induction fields. The solution is presented in the form of attenuation and height-gain curves for both vertical and horizontal polarizations and covers the spectrum from dc to 1 GHz. The quantitative effects of soil conditions are investigated by comparing propagation over good earth with propagation over the extremes of dry sand and sea water.
Magnetic Fields of Twisted-Wire Pairs
On the basis of an expression given by Buchholz for the magnetic-vector potential for an infinitely long twisted-wire pair, the expressions for the external component-flux densities in cylindrical coordinates have been developed. These expressions checked very well with data obtained in the proximity of precisionwound twisted-wire pairs. A generalized graph for various radii and pitch lengths has been developed to enable the design engineer to quickly predict the strength of the magnetic field for all three spacial components at distances in the proximity of a twisted-wire pair.
Correction to ¿Received Voltage Versus Antenna Height¿
A New Method for Calculating Probabilities of Errors Due to Impulsive Noise
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Editorial
On the Capacity of Randomly Used Shared Channels
The channel capacity of a communication channel made available to a user on a shared basis with other users is here considered. An overall system bandwidth B is divided into segments and parceled out to subscribers in an overlapping manner. Viewing emissions by the sharing user as Gaussian noise, the channel capacity is treated as a random variable, and its probability function, mean, and variance are studied. For a fixed power to each user, it is found that the average capacity of a user is maximum when the number of multiple assignments of a frequency band is approximately the inverse of the probability of use. The increase in channel capacity over exclusive assignment is also determined. The probability function of the capacity is worked out for some specific case to show its dependence on the frequency assignment policy, and a general procedure for determining the probability function is given.
Instrumentation Problems Encountered Making Man-Made Electromagnetic Noise Measurements for Predicting Communication System Performance
One of the factors involved in communication system performance is the electromagnetic interference environment (broad-band radiated electronic noise). Attempts are often made to use commercially available radio-frequency interference field intensity meters for these measurements. Measurements made with these instruments are of limited use since detector functions like peak and quasi-peak are not useful parameters in statistical communication theory. It is recommended, instead, that rms voltage be measured simultaneously with average voltage and average logarithm of the voltage. These latter three parameters may be used to infer the amplitude probability distribution, which is a required statistic for predicting the performance of communication systems. Data are given on dynamic range requirements for accurate measurement of these statistical parameters for a given man-made noise sample. An Appendix contains several hardware solutions to the problems posed in this paper.
Reception of Nonhomogeneous Signal Fields in the Presence of Homogeneous Noise Fields
The reception of a nonhomogeneous signal field embedded in a homogeneous noise field, using a simple two-element subtractive array, is studied. For element spacing which is small compared to both the distance to the source and to the center-frequency-wavelength, the signal-to-noise improvement over a single element is shown to be independent of element spacing d, relatively independent of bandwidth and the noise spatial distribution, and to depend only on the distance to the signal source in wavelengths and on the signal ground-wave attenuation rate.
An Accurate Representation of the Complete Electromagnetic Field in the Vicinity of a Base-Driven Cylindrical Monopole
An accurate numerical representation of the electromagnetic field in the near zone of a cylindrical monopole oriented perpendicular to a highly conducting ground screen and driven at its base is needed for use in calibrating field strength measuring equipment. The fields H¿(p,z), Ep(p,z), and Ez(p,z) are given by different integrals. The integrands are formed by multiplying the current distribution Iz(z) by certain derivations of K(p, z ¿ z') = e-jÿR/R taken by hand, where ÿ is the radian wavenumber and begin{equation*}R = sqrt{(z - z^prime)^2 + p^2}.end{equation*}. Alternatively, the integrands may be constructed by multiplying K(p,z - z') by certain derivatives of Iz(z). The current Iz(z) is obtained by solving an integral equation with feedpoint correction employing a linear zoning technique. Generally speaking for a tubular monopole, the current may be obtained to any desired accuracy, and, of course, it is bounded at the driving point. The integrands are then formed, and the resulting integral expressions for the fields are evaluated using a digital computer. By this means it is felt that accurate numerical values of the fields H¿(p,z), Ep(p,z), and Ez(p,z) in the vicinity of the monopole are found, excluding observation points near the feedpoint and end of the radiator. A brief discussion of the methodology employed in programming the Chang theory is presented.
Radiolocation Experiments in an Urban Environment
Many new urban applications of radiolocation technology in both cooperative and noncooperative forms are anticipated in law enforcement and urban planning fields. Until recently, virtually no data were available regarding passive radiolocation of urban targets by conventional techniques such as direction finding. Recent radiolocation experiments performed at 165 kHz and 100 MHz were used to measure transmitter locations with increasing urbanization. Urban radiolocation errors in range and azimuth as a function of urbanization are given for the downtown area of San Antonio, Tex., showing increasing error with increasing urbanization. Procedures to improve urban radiolocation performance are suggested.
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Editorial
A Realistic Approach to Defining the Probability of Meeting Acceptable Receiver Performance Criteria
A statistical model for establishing the probability of being able to successfully communicate is developed. The model is based on requirements for meeting both a specific signal-to-interference criterion and a specific signal-to-noise criterion, and takes into account the correlation that exists in the variations of desired and undesired path loss.
Modeling of Fields Produced by Currents on Power Supply Wiring
Measurements of local fields produced by simulated sources of conducted noise show good correlation with data from three theoretical models: a) an electric dipole, b) a magnetic dipole, and c) a parallel wire transmission line, depending upon the configuration of the source and its ¿ground.¿ The significance of the ¿common-mode¿ current below about 2 MHz is demonstrated.
A Model for Currents and Voltages Induced Within Long Transmission Cables by an Electromagnetic Wave
A model is presented for determining the transient currents and voltages induced within a long coaxial cable by a uniform plane traveling wave whose variation with time may be specified. The cable may be located above or within a half-space lossy dielectric with the wave incident from the half-space lossless dielectric. This results in a model for either aerial or buried cables with the source of the wave located in the atmosphere. A method is also presented for generalizing the approach to more complex cables encountered in communication systems. A demonstration of the applicability of this model is presented by analyzing the response of a 0.375-in coaxial cable for both aerial and buried situations. An incident electromagnetic wave with a rectangular time domain waveform is used to demonstrate the transient response. This waveshape is adequate to clearly indicate the transient phenomena. It is found that voltage enhancement results in both aerial and buried cables when the incident wave approaches grazing incidence. This voltage enhancement can be significant especially for aerial cables. Cable shield current enhancement also results for an aerial but not for a buried cable.
Line Impedance Measuring Instrumentation Utilizing Current Probe Coupling
The theory and instrumentation designed to measure the loop impedence of a power line are discussed. The theory of the system is derived first, followed by a discussion of the instrumentation, and finally an evaluation of the system accuracy is given.
Short-Term Time Characteristics of Atmospheric Radio Noise Above Different Thresholds
Short-term time characteristics of burst and quasi- continuous forms of atmospheric radio noise were investigated at Bangalore at a number of frequencies in the range 100 kHz-9 MHz and over a 300-Hz-16-kHz range of bandwidth. It was found that for all frequencies, bandwidths, and threshold levels the duration and spacing follow log-normal distributions. The duration of a pulse above a particular threshold is statistically independent of its spacing from an adjacent pulse. Further, the average duration varies approximately linearly with the threshold level. These results are expected to be of use in planning digital communications where atmospheric noise is the limiting factor in reception capability.
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Excitation of a Coaxial Line Through a Transverse Slot
A rocket with removed access plate is simulated by a section of coaxial transmission line with a transverse elliptical slot cut in its sheath. The internal circuit consists of two arbitrary impedances in series with the inner conductor at its ends. The object is to find the currents in these impedances when the cylinder is illuminated from the outside by an electromagneticfield that enters the aperture and excites the internal circuit. The problem is solved by application of the reciprocal theorem. The current in a dipole antenna is determined when this is inthe far field maintained by the slotted coaxial line when driven by a generator in series with one of the load impedances. The field in the aperture is replaced by equivalent electric and magnetic dipoles. The reciprocal theorem gives the current in the load impedance when the distantdipole is driven. A numerical example is given.
Use of Four-Level Phase Modulation for Digital Mobile Radio
The paper explains the advantages of and compares various forms of four-level phase modulation from the point of view of performance, implementation, and spectrum usage. The results are applicable to digital mobile radio systems employing a large number of transmissions in which cochannel and adjacent channel interference are experienced. Of particular interest is the extent to which the theoretical spectra may be realized with practical transmitters. Differences between theoretical spectra and those measured from practical power amplifiers are identified. A method of simulating the effects of power amplifier nonlinearities is described and results are presented which agree closely with measurements made on an actual power amplifier.
Comments on ¿The Radio Interference Field of an Overhead Transmission Line¿
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Image Theory Results for the Mutual Impedance of Crossing Earth Return Circuits
Suitable engineering expressions for the mutual impedance of crossing earth return circuits are derived by employing finitely conducting earth image theory techniques. It is shown that the image theory and previously derived analytical results, which are rather complicated, are in excellent agreement.
ELF Earth Return Coupling Into Power Systems
With the advent of the U.S. Navy's proposed ELF Communications System (Sanguine System), which would use an earth-return circuit to excite the earth-ionosphere cavity, earth-return current coupling into power systems has become important. The theoretical basis for coupling into power distribution systems is developed. A comparison is made between measured and predicted values of the induced voltage. Techniques which are useful in eliminating the effects of the induced voltage are described. The effectiveness of these interference mitigation techniques is demonstrated by comparing measurements on actual systems. Finally, data on power system interference are developed for use in communication system design tradeoff studies.
Mitigation of ELF Interference on Telephone Lines
To mitigate the inductive interference on telephone lines exposed to the electromagnetic environment generated by the SANGUINE System, the commercial telephone plant located in the vicinity of an experimental ELF antenna system in Wisconsin was modified by using neutralizing transformers. Compatible operation of telephone system during SANGUINE operation is assured by this technique as evidenced by the continuing virtually interference-free performance of the modified plant.
ELF Earth Return Current Coupling
The theory for predicting the coupling between long line earth-return circuits and extremely low-frequency earth-return sources is reviewed. This theory is based on a uniform earth model. The electric fields predicted by this theory are then compared to a sampling of experimental data derived from long probe wire measurements.
Walsh Function Generators for Minimum Orthogonality Error
The design procedure of a new synchronous counter type of Walsh function generator for the generation of a set of Walsh functions with the least possible error in orthogonality is developed. Each flip-flop of the counter generates synchronously one particular Walsh function in the interval 1 of normalized time during one cycle of counting. The usual design procedures for synchronous counters are not applicable because of the large number of logic variables. Using a two-dimensional plot of the enabling inputs, it turns out that the T flip-flop is the most suitable type. It is shown that by using the symmetry properties of the enabling input patterns for a generator consisting of n T flip-flops, only (log2 n)- 1 standard time sequences, from which the remaining could be derived, need be generated. These time sequences can be easily obtained by decoding the outputs of those flip-flops generating the subset of Rademacher functions. The procedure is illustrated by taking an example of the generation of the first 16 Walsh functions.
Cable Shielding Performance and CW Response
We show that the reference for the measurement of the shielding performance of a cable sheath should be the sheath current. However, unless the phase length of the cable is short, the response at the ends of the line will be sensitive to frequency even if the sheath current is uniform, and the coaxial line formed by the core wires and the sheath is matched at both ends. This is because the driving field in the coaxial line and the waves that it generates have different phase speeds and directions. We present supporting experimental data. Because of this effect it is not meaningful simply to state that a cable provides a specifled attenuation, except for a cable that is short at the highest frequency of interest. We discuss the effects of connectors and of cracks or holes in the sheath. Because the total leakage is proportional to the sum of leakages through the sheath (the connectors and the cracks) and not to their product, it is necessary to assign these contributions with some arbitrariness in order to compare them in decibels. We give an example that shows the importance of RF-tight connectors.
Surface Transfer Impedance Measurements on Subminiature Coaxial Cables
The surface transfer impedances (STI) of several flexible subminiature coaxial cables, such as RG-174/U and RG-188/U, plus smaller coaxial shielded wires, were measured to determine EM shielding characteristics. The results cover the frequency range 0.1-50 MHz and correlate well with previous theoretical models and with experimental values for larger cables, such as RG-58. Copperbraided subminiature cables had STI values 2-5 times larger than those for RG-58
Frequency Assignment Games and Strategies
The way the spectrum is committed through the processes of allocation and assignment has a definite bearing on spectrum utilization. Both processes are stochastic in nature and nearly irreversible. Decisions are made with respect to each applicant as time progresses without knowing the requirements of future applicants, and it is difficult, if not impossible, to revoke or change an assignment once given. This paper examines the frequency assignment game to determine the effect of assignment strategy on spectrum utilization, and to define the principle underlying the development of optimum strategies. The results of this investigation show that there is an effect of strategy, that the effect bears on spectrum utilization, that there is an optimum strategy, and that there are some very useful near-optimum ones as well. Finally, there is evidence that we may not be doing things quite the right way, and some recommendations are offered.
The 1973 CISPR Plenary Assembly at Monmouth College, New Jersey
Comments on "RF Impedance of Power Lines and Line Impedance Stabilization Networks in Conducted Interference Measurements"
Effect of Receiver Bandwidth on Waveforms and Time Characteristics of Atmospheric Radio Noise Bursts
Several investigators have presented the results of their experimental investigations and theoretical expectations on the effect of receiver bandwidth on the time characteristics and waveforms of atmospheric radio noise bursts. The experimental and theoretical findings do not appear to agree with each other. This communication offers a possible explanation for this "discrepancy" with support from experimental evidence, drawn from a large number of references included in this communication.
Maximum Ez-Field of a Dipole and Monopole
For the two-set comprising a dipole and a monopole where the monopole is exactly half of the dipole, the monopole produces the same maximum Ez field as that produced by the empty space dipole, for one-half the input and radiated power.
Test Fixtures for RF Susceptibility Testing
The most likely standard test fixture for RF susceptibility testing is the twin-strip transmission line, or its half-space counterpart. Its capacitance per meter (length) is 2¿ or 4¿; characteristic impedance Zc= Z0/2 or Z0/4; voltage gradient Ez = V/w or 2 V/w; magnetic field Hy = V/w Z0 or 2 V/w Z0, respectively.
Correction to ¿Multiconductor Antenna Transmission Lines with Arbitrarily Positioned Load Impedances in an Incident Field¿
Correction to ¿The Use of the Lorentz Reciprocity Theorem to Prove Equality of the Open-Circuit Voltages of a Receiving Dipole and a Monopole¿
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Generation of Standard EM Fields Using TEM Transmission Cells
A new technique developed at the National Bureau of Standards (NBS) for establishing standard, uniform, electromagnetic (EM) fields in a shielded environment is described. The technique employs transverse electromagnetic (TEM) transmission cells that operate as 50 ¿ impedance-matched systems. A uniform TEM field is established inside a cell at any frequency of interestbelow that for which higher order modes begin to propagate. Standard field strength levels from 10 ¿V/m to 500 V/m can be established with uncertainties of less than 1.0 dB to 2.0 dB inside the NBS cells for frequencies from dc to 500 MHz. The cells are especially useful for calibrating EM radiation hazard meters, for emission and susceptibility testing of small to medium sized equipment, and for special low level calibration of very sensitive field strength meters.
The Response of a Two-Wire Transmission Line Excited by the Nonuniform Electromagnetic Fields of a Nearby Loop
Equations are derived for the currents in the load of a two-wire transmission line illuminated by the nonuniform fields of a small coplanar loop. Since the derived equations contain complicated integrals requiring machine computation, an approximate solution, which is applicable to most coupling geometries and which greatly reduces the computational effort, is also developed. In a numerical example, the currents excited by the loop are compared with the currents excited by a plane wave.
Shielding Properties of Thick Conducting Cylindrical Shells
The shielding properties of a thick cylindrical shell of finite conductivity is presented. The analysis uses straightforward separation of variables methods via cylindrical harmonic functions. The results show that significant attenuation of the incident fields are achieved for thick cylindrical shields thus demonstrating that the resonances noted in earlier work using thin shell models can be alleviated.
Electromagnetic Field Penetration into a Spherical Cavity
A plane wave is symmetrically incident on a spherical shell with a circular aperture. The fields inside and outside the cavity are expanded in terms of spherical vector wave functions and the modal coefficients are found by application of the least squares method to the boundary conditions. Computed data are obtained and the results exhibited in the form of amplitude curves of the interior and aperture fields as functions of position for a variety of cavity and aperture sizes. Within the cavity it appears that the field variations are primarily determined by the cavity size and that the aperture size serves only to scale them.
Evaluation of the Surface Integral Occurring in the E-Field Integral Equations for Wire Antennas
The method for performing an exact surface integration for the E-field integral equations is outlined, and a comparison with the often used thin-wire approximation is made. It is found that for pulse type basis functions, the thin-wire kernel is valid for cell sizes greater than about eight wire radii, with an overall error in the kernel less than one percent.
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Attenuation Measurements in the 1 to 1000 MHz Frequency Range in Wet Granite Tunnels
Attenuation measurements were made in the 1 to 1000 MHz frequency range in two wet-granite tunnels leading to an underground facility. The purpose of the measurements was to determine the vulnerability of the facility to interfering electromagnetic radiation. Continuous-wave signals were propagated within the tunnels and the signal levels at various distances from the transmitter were measured with a spectrum analyzer. Measurements were made using antennas to launch and receive the signals and also using baluns to conduct the signals directly to longitudinal metallic structures. These structures consisted of ventilation ducts and of the sheaths on power cables and coaxial cables. At low frequencies, the path attenuation was on the order of 2 dB/100 ft. (0.07 dB/m). The results show that this low attenuation probably resulted from the presence of the longitudinal metallic structures in the tunnels. The maximum path attenuation occurred at 50 MHz in one tunnel and at 200 MHz in the other (smaller tunnel). Then, at higher frequencies, it is thought that propagation occured in a waveguide-like manner. At the higher frequencies, it was found that bends in the tunnels significantly increased the attenuation. It is concluded that if interfering signals in the MHz range are anticipated, tunnels free of longitudial metallic structures should be used. To prevent interference by higher frequencies, where waveguide-like propagation occurs, tunnels should contain bends.
Electric Field Probes in Material Media and Their Application in EMC
The use of the linear antenna as a probe to measure both the constitutive parameters of material media and the electric field interior to such media is reviewed. The advantages of using probes with a particular geometry (i. e., electricaUy short, resonant, bare or insulated) for specific applications are discussed. Applications in the areas of geophysics and biophysics are cited.
Light Transmittance and RF Shielding Effectiveness of a Gold Film on a Glass Substrate
Light transmittance and the Rf shielding effectiveness of a gold film on a glass substrate is investigated. The dependence of the transmittance of visible light upon the thickness or surface resistance of a gold film on a glass substrate is determined numerically by the optical properties of the gold film and glass substrate. The Rf shielding effectiveness produced in the far field over the frequency range of 100 MHz to 30 GHz by the gold film is calculated and compared with experimental data. An optimum condition is established between the light transmittance and the shielding effectiveness. The results are applicable to any transparent glass coated with any thin metallic film.
Microwave Interference Effect in Bipolar Transistors
This work discusses the active circuit behavior of typical bipolar transistors as they are injected with low level microwave energy. The observed response is found to be due to square law rectification of the energy at the transistor's emitter-base junction. A rectification efficiency measurement'is described which gives a quantitative measure of a transistors sensitivity to microwave interference in terms of an equivalent rectified base current interference signal per unit of absorbed microwave power. Measurements show that a typical n-p-n Si planar transistor (FT = 450 MHz) has a rectification factor of approximately 0.05 mA/mW for 2 GHz microwave energy. Typically, this factor decreases at about 6 dB/octave as the interference carrier frequency is increased. A model for the rectification effect is propQsed which suggests that it is due to ac crowding and the decrease in transistor a at the edges of the emitter, in addition to the basic nonlinearity of the emitter-base junction volt-ampere characteristic.
The RF Pulse Susceptibility of UHF Transistors
The electromagnetic susceptibility of UHF transistors is investigated. The 2N5179 RF amplifier type transistor was selected as a representative UHF transistor because of its chip structure. It is a silicon n-p-n epitaxial planar transistor with an interdigitated baseemitter metallization pattern. Several manufacturer's versions were tested. A single RF pulse at 240 MHz was applied directly to the base terminal with the emitter terminal grounded. The incident RF pulse power required to cause a 50 percent failure rate is in the 35-70 W range for a 3 ¿s pulse duration and in the 150-450 W range for a 0.3 , ¿s pulse duration. The primary variable is the percentage of the incident power absorbed by the transistor. The absorbed pulse energy required to cause a 50 percent failure rate is in the 20-35 ¿Joule range for 0.3-3.0, ¿s pulse durations. The gs pulse and CW RF burnout powers for 2N5179 transistors are similar to those for 1N23 mixer diodes. The data suggest that UHF receivers with an RF transistor amplifier front end may be as susceptible to intense EMR at UHF frequencies as are UHF receivers with a mixer diode front end.
ATS-6 Spacecraft Surface Treatment for the Control of Electrical Discharges
The Applications Technology Statellite-6 (ATS-6) has successfully withstood repeated entrances into and exits from occult in a period centered on the 1974 autumn equinox, during which it was subject to potential changes as hikh as 11 000 volts based on onboard measurements. Much of the outer surface of the spacecraft is an insulator, dictated by thermal control design. Consequently, special measures were required to protect the spacecraft, and especially its commmand receiving system, from electrical dischargesp whose accompanying fields could destroy sensitive receiving circuits. This paper describes the thermal blanket grounding criteria applied to prevent undesired discharge effects.
The Effect of Cylindrical Ferromagnetic Shells on the Self and Mutual Inductance of Parallel Wires
The effect of ferromagnetic shields on the self and mutual inductances of the wires enclosed by a ferromagnetic shell has been theoretically analyzed. Some theoretical equations based on a simplified model, which assumes that the driving wires and returning wires are located within two separated magnetic shells, are derived. The analysis shows that the effect of the ferromagnetic shells on the inductance of the wires depends strongly on the separation of the two magnetic shells; the closer the two magnetic shells, the stronger the effect. For a configuration of two identical ferromagnetic shells of internal radius 0.65 cm and separated by 10 cm, it is estimated that the self and mutual inductances are increased by about 30 percent for a wire of radius 0.06 cm. The changes of the self and mutual inductances are essentially due to the interactions between the ferromagnetic shells and the induced fields of the current elements.
Computation of the Capacitance Matrix for Systems of Dielectric-Coated Cylindrical Conductors
The method of moments is applied to the computation of the charge distributions and capacitance matrix for electrostatic systems of bare and dielectric-coated cylindrical wires. Several choices of expansion functions are investigated in detail and compared. Harmonic series expansion functions are shown to be especially well suited to problems involving systems of closely-spaced dielectric-coated cylindrical wires.
Compatibility and the Frequency Selection Problem
An automated model that calculates the frequency separation requirements for interference free operation of electronic systems located in a given environment is described. Using these frequency separation requirements, the model assigns a channel to each system in the environment based on the frequencies available to each. The model calculates inter system, antenna coupled interference levels only. It uses an iterative, but nonexhaustive, process which attempts to develop a compatible assignment. Preassignment checks are performed to determine if a complete assignment is impossible based on the number of frequencies available to each system and the separations between these frequencies. If an assignment is impossible, a partial assignmnent with the least number of deletions restults. Using the preassignment checks, the model can be used to determine a channel scheme for a new system that will conserve spectrum space and allow compatible operation in any given environment. The results of a recent application of the model to an environment of microwave landing guidance systems including the proposed MLS is given.
Analysis of Crossed Wires in a Plane-Wave Field
The currents and charges induced in a pair of electrically thin crossed wires by a normally incident plane electromagnetic wave are derived by analytical methods. The boundary conditions at the ends and at the junction are explained. The solution of a new integro-differential equation for the currents is obtained in terms of trigonometric and integral-trigonometric functions. Depending on the electrical lengths of the crossed elements and location of their junction a variety of quite different distributions of current and charge obtain. These determine the scattered near and far fields. Graphs of computed currents and charges per unit length on the four arms of several important cases are displayed. The accurate determination of the induced currents and charges on a mathematically tractable structure-the thin-wire cross-is an early step in a study that will proceed to electrically thick cylinders, wide strips, and their junctions in crossed configurations in an effort to gain a meaningful approximate understanding of the currents and charges induced on an aircraft by an electromagnetic pulse.
Walsh-to-Fourier Spectral Conversion for Periodic Waves
Relations are developed for the determination of the Fourier spectra of frequency-limited periodic waves from truncated Walsh spectra. The matrix conversion process is simplest if the highest-order Walsh coefficient in the spectru to be converted is 2n, where n is an integer. For such cases, compensation for truncation consists of a diagonal matrix that premultiplies the Walsh to Fourier conversion matrix and the elements of which are [(sinx)/x]-2 terms. Element values range between unity and less than ¿2/4. The same compensation matrix is used for determning the Walsh spectra. of sequency-limited waves from 2n Fourier expansion terms. Examples are included which demonstrate the spectral conversion processes, Walsh to Fourier and Fourier to Walsh.
New Developments in CISPR-Results of the EMC Symposium in Montreux
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Radiation Characteristics of Electrically Small Devices in a TEM Transmission Cell
When making EMC measurements inside a shielded enclosure, the radiation characteristics of the device being tested changes. In this paper, the change in radiation resistance of dipole sources located inside a National Bureau of Standards TEM transmission cell is determined. In many cases a practical device can be modeled by dipole sources. In these cases the analysis allows one to predict the device's radiation characteristics in other environments (e. g., free space).
A Lossy Element for EMC Filters
The need and advantages of lossy elements in unconditional EMC filter design are well recognized. This paper describes a lossy device based on the proximity effect using multilayer strip lines. Expressions are derived for the losses in the multilayer strip conductors. Experimental data show good agreement with theoretical expectations when the differences between the theoretical model and actual implementations are taken into account. The formula for an infinite stack provides a theoretical upper limit to the losses as a function of frequency. A modified empirical formula provides a practical design equation. Applications are also discussed.
RF Shielding Effectiveness and Light Transmission of Copper or Silver Film Coating on Plastic Substrate
RF shielding effectiveness and light transmittance of acopper or silver film coating on a plastic substrate is investigated. The dependence of the RF shielding effectiveness upon the surface resistance or thickness of a copper or silver film coating on a plastic substrate is calculated numerically by means of multireflection transmission-line theory over the frequency range of 100 MHz to 30 GHz. The light transmansmittance is determined by using the optical properties of the copper or silver film and plastic substrate. An optimum condition between the RF shielding effectiveness and the light transmittance is established for the copper or silver film coating on a plastic substrate.
On the Electromagnetic Field Penetration Through Apertures
A numerical method is presented for determining the electromagnetic field diffracted by an aperture in an infinite conducting plate. Comparisons are made with the results of approximations valid at low frequencies and high frequencies. Calculations of the electromagnetic field components in the aperture, in the near zone of the aperture, and in the far zone of the aperture are made and are compared with available measured data
Statistical Prediction Model for EMC. Analysis of Out-of-Band Phased Array Antennas
A statistical model was developed for predicting and describing the out-of-band pattern characteristics of phased arrays containing ferrite phase shifters. Statistical analysis techniques are necessary because experimental investigations showed that the propagation of higher-order modes at out-of-band frequencies cause phased arrays containing ferrite phase shifters not only to respond differently at out-of-band frequencies but also to exhibit random behavior. Equations were derived which relate the out-of-band pattern scanning properties, relative gain levels, median gain, and standard deviation to the in-band scan angle and the ferrite phase shifter statistics. Computer algorithms were written to both compute and graphically display the out-of-band antenna patterns. Experimentally derived phase-shift data were used as inputs to the model. The results of these investigations show that statistical analysis techniques are potentially very useful in an EMC context for characterizing out-of-band responses of phased array antennas
Analysis of Radio Frequency Transmission along a Trolley Wire in a Mine Tunnel
An idealized model of a trolley wire communication system in a tunnel is considered. To facilitate the analysis the tunnel cross section is taken to be semicircular and the surrounding rock medium is homogeneous with a finite conductivity. The metallic rails or other conductors on the flat floor of the tunnel are represented by a plane metallic reflecting surface of infinite extent. The trolley wire and associated feeder line are assumed to be equivalent to a single cylindrical conductor that is parallel to the axis of the tunnel but located anywhere within the cross section. The appropriate modal equation is then solved for the propagation constant of the dominant mode. It is shown that the attenuation rate increases significantly as the trolley wire approaches the tunnel wall. However, even when the trolley wire is within 20 cm (8 in) of the wall, the attenuation rate at 200 kHz is still less than 2 dB per kilometer.
Computation of the Transmission Line Inductance and Capacitance Matrices from the Generalized Capacitance Matrix
In a recent paper [1], a method for computing the per-unitlength generalized capacitance matrix of a system of dielectric-insulated wires was given. In this-paper, a method for computing the per-unitlength inductance and capacitance matrices used in multiconductor transmission-line models in terms of the elements of the generalized capacitance matrix is given. Certain approximate formulas for large wire separations are also given. Rome Air Development Center.
Frequency Response of Multiconductor Transmission Lines Illuminated by an Electromagnetic Field
A well-known result [1], [2] for the response of a two-wire transmission line illuminated by a nonuniform electromagnetic field is extended to multiconductor lines. A simple matrix equation for the currents induced in arbitrary termination networks is obtained. Air Development Center.
On the Current Induced within an Infinitely Long Circular Cylinder (or Wire) by an Electromagnetic Wave
The current induced by a harmonic electromagnetic plane wave in an infinitely long wire is discussed. Two methods of calculating this current for a wire situated in vacuum will be compared: 1) one by Mohr [1] and 2) a direct calculation, which is given in Section II of this paper. Mohr's method 1) utilizes transmission line theory and the case of perpendicular incidence discussed in Jordan's book [2]. In the direct method 2) only Maxwell's equations and boundary conditions are used. When the direct method is presented in Section II, the wire is assumed to be situated in an arbitrary infinite homogeneous medium, not necessarily in a vacuum. In fact the direct method allows also the thickness and the material of the wire to be arbitrary, and so any infinitely long circular cylinder can be considered. It seems that the currents determined by Mohr's method and the direct method have roughly the same order of magnitude (at least), if the electromagnetic wave has a high-altitude-EMP frequency and is incident on a copper wire whose radius is less than about 1 cm and the angle between the line and the direction of propagation of the wave is above 45 ° . The agreement between Mohr's method and the direct method is better, the more perpendicular the incidence, the lower the frequency, or the smaller the radius of the wire.
On Generating Walsh Spectrograms
A simple method for generating a class of time-sequency-amplitude plots called Walsh spectrograms is presented. A Fortran computer program which enables one to generate such spectrograms readily is provided. Illustrative examples related to generating spectro-grams associated with pulse-code modulation and speech data are included.
Expansion of Walsh Functions in Terms of Shifted Rademacher Functions and Its Applications to the Signal Processing and the Radiation of Electromagnetic Walsh Waves
The expressions for Walsh functions in terms of shifted Rademacher functions are applicable to the design of a directive and selective array antenna for Walsh waves which is capable of eliminating the interference caused by impulsive noises. They also are applicable to voice processing because of their shift-invariant property. The shifted Rademacher functions were previously introduced by shiftiAg horizontally the periodic Rademacher functions. It was shown that the Walsh functions could be expressed as a linear combination of a finite number of the shifted Rademacher functions. This paper develops the actual expansions of the Walsh functions in terms of the shifted Rademacher functions. The coefficients in this series take only the values of either + 1 or -1. The shifted Rademacher coefficients appearing in the expansion of a given function in tenns of shifted Rademacher functions have the advantage that the coefficients of a shifted function are available by shifting cyclically the original coefficients.
Comments and Corrections on "Use of a Reverberating Enclosure for Measurements of Radiated Power in the Microwave Range"
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Parametric and Synoptic Charts for Determining the Patterns of an Elemental Dipole with a Scattering Mirror or Cylinder
It is shown that a comprehensive summary of the dependence of the patterns of a "complex" antenna system on its geometric and electrical parameters can be presented in graphical form through the use of what are here described as "parametric graphs" and "synoptic charts". Such graphical descriptions may be readily derived, provide an overall understanding of a system's behavior, enable economic and rapid determination of patterns, and permit comparison between different antenna systems. The examples presented are for the cases of an elemental dipole with a finite mirror or cylinder, and for the classical two-element array.
EMI Survey for Maritime Satellite 1535-1645-MHz Shipboard Terminal
The United States Lines' 15 690-ton commercial-container ship, "American Alliance," was selected as lead ship for an onboard EMI survey prior to installation of 1535-1645-MHz (L-Band) shipboard terminals for communication via a maritime satellite. Three maritime communications satellites are currently in orbit: Marisat-1, over the Atlantic Ocean at 15° W. longitude, Marisat-B, over the Pacific Ocean at 176.5 E. longitude, and Marisat-C, over the Indian Ocean at 73° E. longitude. In general, the EMI survery revealed tolerable interference levels onboard ship: radiometer measurements indicate antenna-noise temperatures less than 70 K, at elevation angles of 5° and greater, at 1559 MHz, at the output terminals of the 1.2-m diametci, parabolic-dish antenna for the L-band shipboard terminal. Other EMI measurements include field intensity from 3-cm and 10-cm wavelength pulse radars, and conducted-emission tests of primary power lines to both onboard radars. This information should be helpful to designers of maritune L-band shipboard terminals.
Electromagnetic Shielding Effectiveness of Steel Sheets with Partly Welded Seams
The effect of single welding flaws on the electromagnetic (EM) effectiveness of welded steel enclosures has been assessed. The possibility of resonant reradiation by these flaws has been examined, using resonance calculations and direct EM measurements. Using these results, a method was developed for assessing shielding quality of hardened military structures, such as SAFEGUARD sites, and EM shielded enclosures. The effect of four formns of incomplete welds on the shielding effectiveness of welded steel enclosures was determined for single flaws. Electromagnetic shielding effectiveness tests (from 10 kHz to 10 GHz) were made on various test specimens of 11-gauge steel plate. These test specimens included butted plates with incomplete welds and plates with single holes and slots cut into them. Tests simulated the worst cases of cracks, lack of fusion, and porosity. Shielding effectiveness as a function of flaw size was determined for each defect, and a critical or transition flaw size was determined for each of three frequency bands and at the 100-dB shielding level for each type defect. The measured results were compared to a calculated resonance response by modeling the flaws as slot antennas.
Alteration of the Surface Current on a Missile by the Presence of an Exhaust Plume
This paper presents an analysis of a missile with an exhaust plume when exposed to an incident electromagnetic plane wave at an arbitrary angle of incidence. Both homogeneous and axially inhomogeneous plumes are considered. For the inhomogeneous case, the AeroChem low altitude plume program is used to provide realistic values of the electrical properties along the length of the plume. In the analysis, the missile and the plume are assumed to be thin when compared to the length of the missile and the wavelength of the incident radiation. Conventional numerical methods developed for thin-wire antennas are used to determine the current in the missile and the plume, and the effect the plume has on the current is examined. Field patterns for aperture coupling at specific points on the missile are also presented. A limited comparison with measured results is presented.
Near-and Far-Field Thin-Wire Coupling¿Theory and Expeiment
The method of moments is applied to near-and far-field coupling problems for thin-wire antennas with arbitrary orientation, excitation, and loading. A coupling matrix is derived. The analysis method is validated by the results of an extensive experimental program. Comparisons are made between theory and experiment for coupling from monopole to monopole, dipole to dipole, and dipole to dipole in the presence of parasitic elements. Special approximate formulas are developed for parallel thin-wire dipoles and monopoles. The moment methods permit accurate computation of antenna coupling in a wide variety of situations.
Electromagnetic Scattering from an Unbonded Retangular Wire Mesh Located near the Air-Ground Interface
Using an earlier numerical formulation, we present results for the reflection characteristics of the wire mesh located just above the air/ground interface. The influence of the various parameters, such as angle of incidence, interwire spacing, wire radii, height of wire mesh, and ground conductivity is investigated. Both square and rectangular meshes are considered. An important finding is that the reflecting efficacy is only slightly degraded when the mesh is moved from, say a height of six wire radii down to a height equal to one wire radius. Farfield radiation patterns for source dipoles of various orientation, located over the mesh, are also calculated. These are compared with the corresponding patterns for a ground surface with no mesh present. The major differences occur at grazing angles, as expected. Also in this region, some of the approximate formulations, such as those based on the average boundary condition techniques used by the Soviets, break down.
Design of a Synchronous Walsh-Function Generator
Recent development of circuits for generating parallel-programmable and serial-programmable Walsh functions with a high degree of orthogonality is discussed. The realization of these circuits leads to the demand for highly integrated digital circuits with multiple outputs triggered synchronously. Circuits capable of high speed and low input power have just recently come into production. The application of low-power Schottky integrated-circuit logic in the design of a 10-Mzps parallel-output array generator for Walsh functions is presented here. The circuit is designed, built, and tested and the orthogonality error for the Walsh functions is discussed.
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An Optically Linked Telemetry System for Use with Electromagnetic-Field Measurement Probes
A battery-powered optical telemetry transmitter, 2.5 X 2.5 X 3 cm, has been developed for use with various electromagneticfield hazard probes. The electrical outputs from one of these probes, containing three orthogonal sensors, are electrooptically converted to three separate optical pulse trains so that a dc to 2-kHz information bandwidth is established in the transmitter using frequency-modulation techniques. The three optical pulse tains are transmitted over a 4.6-m fiber-optics bundle to one of two types of receivers. These units reconvert the information to either an analog replica of the transmitter input waveform, or to a three-digit, scaled numerical display of the time-averaged value of the input signal. Practical applications involving field-strength measurements in the 1-MHz to 12-GHz region are presented. Advantages over hardwire data links are discussed, and significate reductions in RF interference and cable backscatter during field-strength measurements are described.
Electromagnetic Surface-Wave Propagation over a Rectangular-Bonded Wire Mesh
The electromagnetic surface wave which can propagate over a rectangular wire mesh of infinite extent is considered. The propagaton constant is determined both from a rigorous Floquet formulation and an approximate method using averaged boundary conditions. The agreement is fairly good for sufflciently small mesh dimensions. The rectangular mesh is found to be highly anisotropic, and the possibility of an effective anisotropic transfer inductance representation for the mesh is discussed briefly.
On Electromagnetic-Field Excitation of Unshielded Multiconductor Cables
Unshielded multiconductor cables are considered to be iliuminated by electromagetic plane-wave fields. A study of the currents that are induced in the terminations is made using quasistatic circuit theory, transmission line theory, and wire antenna theory. Questions of accuracy, ranges of validity, and general trends are addressed.
Radio Signals with Large Relative Bandwidth for Over-the-Horizon Radar and Spread-Spectrum Communications
It is known that radio signals must have a small relative frequency bandwidth if structures and circuits resonating with sinusoidal functions are to be used for radiation and reception. This paper develops concepts showing that a small relative frequency bandwidth is also required for the use of amplitude or frequency modulation of sinusoidal radio carriers in the usual form. However, it is easy to modify the usual methods of amplitude and frequency modulation for signals with large relative frequency bandwidth. The primary application of such methods is for over-the-horizon radar and spread-spectrum communications in the short-wave region where the desired relative frequency bandwidths are neither small (in the order of 0.01 or less) nor close to 1.
A Comparison of Test and Model-Predicted RF-Pulse Susceptibilities of UHF Transistors
A semiconductor thermal-damage model was presented previously. Accuracy verification was limited to dc pulses and a damped sinusoidal waveform. Data published on UHF transistors allow additional model verification to RF pulses. 1 Results confirm that dc-pulse data are sufficient to predict RF-pulse damage levels.
A Simplified Computational Technique for Longitudinal H-Field Shielding
A method is described for the calculation of the shielding effect of a set of coaxial circularly cylindrical tubes in an alternating longitudinal H-field. The arrangement is modelled using a nonuniform transmission-line equivalent circuit composed of a number of micro-T-circuits. The use of Bessel functions is completely obviated without loss of accuracy.
On the Walsh-Hadamard Transform and Prime Implicant Extraction
The Walsh-Hadamard transform (WHT) provides a one-to-one mapping of n-variable Boolean functions onto an n-dimensional transform space. As such, it enables synthesis procedures to be carried out in the transform domain. This short paper discusses the role of the WHT in extracting prime implicants, which is pertinent to the overall minimization problem. First, a procedure to identify all the prime implicants of a 1-vertexl located at the origin is developed by inspecting the elements of a single inverse transform. Second, a theorem is proved to show how the signs of the transform coefficients can be changed, to obtain all the prime implicants of an arbitrazy 1-vertex via the same inverse transforn operation.
On the Walsh Analysis of Nonlinear Systems
This paper considers some aspects of the analysis of nonlinear systems via Walsh functions. Two basic approaches are investigated. These are 1) a characteristic-function method which assumes a Walsh-transformable nonlinearity and 2) a matrix method that is suitable when the input can be represented by a truncated Walsh series expansion. Illustrative examples are included.
Economic Efficiency: The Objective of Spectrum Management
The author notes a degree of confusion as to the overall objective of spectrum management. The concepts of spectrum conservation, spectrum efficiency, and economic efficiency are discussed and compared. Economic efficiency is concluded to be the proper objective.
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Further Comments on "Variation in the Surface-Charge Density of an Excitable Nerve Membrane Exposed to Optical Radiation"
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A Modified Ebers-Moll Transistor Model for RF-Interference Analysis
This paper develops analytical techniques for the study of nonlinear RF and microwave effects in semiconductor devices. Rectification in p-n junctions is discussed, and a novel large-signal transistor model is developed, based upon modifications to standard Ebers-Moll formulations for bipolar transistors. Use of the models in worst-case analysis is discussed, with ranges of parameters given based on a simplified analysis of rectification in ideal diodes.
Computer-Aided Analysis of RFI Effects in Digital Integrated Circuits
A computer-aided analysis procedure based upon a modified Ebers-Moli transistor model is used to predict RFI effects in bipolar integrated circuits (IC's). The procedure is applied to a digital IC to determine the RF power levels that cause several EM susceptibility thresholds to be exceeded.
Computer-Aided Analysis of RFI Effects in Operational Amplifiers
The modified Ebers-Moll model is used to predict RFI effects in the 741 operational amplifier (op amp)-a bipolar linear integrated circuit (IC). RFI susceptibility predictions for RF incident upon the op-amp input terminals are made using a complete model, a macromodel, and a voltage-offset model. Both the batch-mode computer program SPICE 2 and the commercial interactive computer program ISPICE are used. The three sets of calculated results are essentially identical and agree within 4 dB with experimental results measured at 220 MHz. A threshold cannot be given for the RF power level at which a 741 op amp is susceptible to RFI. The level depends upon the op-amp circuit application. For op-amp circuits designed to amplify input signals in the 0.1-to 1.0-V range, RF power levels as large as -15 to + 5 dBm may be required to cause RHI susceptibility problems. For op-amp circuits designed to amplify input signals in the 1-to 10-mV range, RF power levels as low as -55 to -35 dBm may cause RHI susceptibility problems.
Modeling of Low-Level Rectification RFI in Bipolar Circuitry
This paper discusses the rectification response exhibited by low-frequency bipolar transistors when microwave energy is injected. A circuit-analysis model for calculating low-frequency small-signal RFI response is outlined and applied in analyzing RFI behavior ofa 741 op amp. Principal results from the RFI-device model are 1) RFI is due basically to nonlinearity of the emitter-base characteristic, and also to ac crowding and nonuniformity of gain across the emitter, and 2) there is a distinct inverse relationship between device size (emitter perimeter) and rectification-RHI sensitivity. Model results and comparison with 741 op amp measurements indicate that the rectification sensitivity to 1-GHz power is approximately 3 mV of offset voltage referred to the device input, per microwatt of absorbed power.
Microwave-Rectification RFI Response in Field-Effect Transistors
This paper discusses the rectification of microwave energy in low-medium frequency feld-effect transistors (FET's) and develops a small-signal model for RHI noise analysis in low-frequency linear circuitry. The modeling procedure centers on a Taylor series expansion of the gate voltage-drain current characteristic which shows a small increase in drain current due to a nicrowave voltage at the gate. The increase in drain current is proportional to the variation in transconductance with gate voltage, and the square of the microwave voltage. Analysis of the microwave power in the transistor shows that critical parameters in determnination of the sensitivity are the gate capacitance and the real part ofthe device input impedance, which ultimately is limited by the parasitic resistance between the active channel and contacts.
Response Coefficients of a Double-Balanced Diode Mixer
This paper presents the results of a computer-assisted analysis of a commonly used double-balanced diode mixer circuit. It is shown that the magnitudes of some of the responses to one or more input radio frequency signals are sharply dependent on the degree to which the diodes comprising the mixer are balanced. The average rejections imparted to a particular undesired intermodulation (or spurious) response by a random sample ofsuch mixers are plotted as a function ofthe tightness ofthe control of diode characteristics of the population from wl lch the four diodes comprising a single mixer are selected. A computer program based on a Fourier-series expansion of the time-dependent coefficients of a Taylor-series representation of the four diode currents was employed to compute the response coefficients of the mixer [1H3] The response coefficients are defined as the magnitudes of the intermodulations of sinusoidal-input radio-frequency signals and the local-oscillator-frequency signal. The method treats the switching action characteristic of the large local-oscillator power levels, rather than relying on the more usual and invalid [1] assumption of " mild" nonlinearity. Orders of nonlinearity up to the tenth are treated.
Predicting Insertion Loss of Common-Core Powerline Filters
Knowledge of the propagation mode and the source impedance is necessary in order to predict the insertion loss of common-core powerline filters. If these quantities are standardized, the transition-band insertion loss corresponding to two test modes can be accurately calculated by use of only a programmable hand calculator, such as the Hewlett-Packard HP65 or Texas Instruments SR56. Such predictions of differential and common-mode insertion loss are of value in designing electronic equipment for conformance to world-wide specifications applying to powerline interference emission and filter leakage current.
Fundamentals of Steady-State and Transient Electromagnetic Fields in Shielding Enclosures
A simplified theory of electromagnetic shielding by enclosures with conductive and/or magnetic wails is presented. The theory is based on a simplified type of boundary condition at the enclosure walls. Theoretical results are compared with exact solutions for steady-state and transient excitation and the approximation turns out to be extremely good in all cases of practical interest. For enclosures of arbitrary shapes, the problem is formulated as a single integral equation in the unknown current in the shield. Numerical solution of the equation is discussed, as well as a possible equivalent lumped-circuit representation.
The Need for Realistic Susceptibility Levels for Radar Receivers
The Definition of Frequency-Dependent Rejection
The frequency-dependent rejection (FDR) terminology is frequently used in EMC analysis, especially in the report literature, and hence it appears useful to discuss it's general definition.
Comments on "Scattering Characteristics of VHF/UHF Television Broadcasting Waves by Overhead Power Transmission Conductors"
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Automated Procedure for Shipboard Exterior Communication RF System Design
This paper describes the design procedure used for Navy shipboard exterior RF communication system design. The approach is an iterative process by which candidate RF-system designs can be analyzed to determine their relative desirability. To support the design procedure, an automated capability has been developed consisting of two system modeling codes and three antenna modeling codes. This automated design procedure also has been applied to nonshipboard cosite communication systems.
Intrasystem Electromagnetic Compatibility Program (IEMCAP)
This paper describes a computerized analysis process (IEMCAP) which may be used to establish and maintain cost-effective interference control throughout the life cycle of systems composed of communications and electronics equipment. The program is capable of both generating system specification limits and maintaining the integrity of the system specification with system modification. The program utilizes MIL-STD-461A1 and MIL-I-6181D EMC specifications ations as a basis for defining the overall system specification limits. The major segments of the program are specification generation, tradeoff analysis, and waiver analysis.
On Contributions at Syracuse University to the Moment Method
A survey concerning contributions of Syracuse University to the "Method of Moments" for treating problems of electromagnetics, netics, particularly electromagnetic compatibility, is presented. Subject areas encompass problems of electrostatics, thin wires and rods, conducting bodies, eigenvalue problems, random electromagnetic etic effects, and other work. Each of these pertains to a number of specific categories of problems, for which computer codes are described and sources identified. References cited number 147.
Summary of GTD Computer Codes Developed at the Ohio State University
This paper briefly describes three user-oriented computer codes developed at the Ohio State University ElectroScience Laboratory: namely, the On-Aircraft Antenna Code, the Basic Scattering Code, and the Reflector Antenna Code. Each code uses the Geometrical Theory of Diffraction (GTD). An example is used to describe the basic GTD approach for all three codes. A brief description is given for each code which includes sample results compared to measurements.
Electromagnetic Models for Antenna Performance, EMC, and Biological Effects
This paper describes several models which have been developed at Georgia Tech for the analysis of antennas, EMC, and biological effects. These models include algorithms based upon the plane-wave-spectrum scattering-matrix analysis, the geometrical theory of diffraction, and the method of moments. In addition, statistical models for antenna coupling, for out-of-band antenna performance, and for scattering by complex structures are discussed. In each case, the model results are compared with measured data to assess the accuracy of the modeling technique.
Using NCAP to Predict RFI Effects in Linear Bipolar Integrated Circuits
Applications of the Nonlinear Circuit Analysis Program (NCAP) to calculate RFI effects in electronic circuits containing discrete semiconductor devices have been reported upon previously. The objective of this paper is to demonstrate that the computer program NCAP also can be used to calculate RFI effects in linear bipolar integrated circuits (IC's). The IC's reported upon are the ¿A741 operational amplifier (op amp) which is one of the most widely used IC's, and a differential pair which is a basic building block in many linear IC's. The ¿A741 op amp was used as the active component ent in a unity-gain buffer amplifier. The differential pair was used in a broad-band cascode amplifier circuit. The computer program NCAP was used to predict how amplitude-modulated RF signals are demodulated in the IC's to cause undesired low-frequency responses. The predicted and measured results for radio frequencies in the 0.050-60-MHz range are in good agreement. Contained in the paper is a complete set of NCAP parameter values for all the transistors in the ¿A741 op amp. These parameter values may be used as typical data for similar transistors in other bipolar integrated circuits.
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