Showing papers on "Electromagnetic compatibility published in 1968"

Some Measurements of the Expansion of a Metallic Cylinder with Electromagnetic Pules

Abstract: Electromagnetic metal-forming is a new process that has been in practical use for the last six years. The optimized design of the electromagnetic forming system is rather involved because of the complex interdependence of all system parameters.

Electric control circuits for electromagnetic devices

Abstract: AN ELECTRIC CONTROL CIRCUIT FOR AN ELECTROMAGNETIC DEVICE SUCH AS CLUTCH OR A BRAKE INCLUDES A FIRST MEANS FOR ENERGISING THE COIL OF THE DEVICE TO OPERATE THE DEVICE AND A SECOND MEANS FOR SUBSEQUENTLY PROVIDING A REVERSE CURRENT FLOW THROUGH THE COIL WHEREBY RAPIDLY TO REDUCE THE ENERGISATION OF THE COIL. THE FIRST MEANS INCLUDES AN ENERGISING CIRCUIT FOR THE COIL HAVING A CAPACITOR AND A FIRST CONTROLLED IMPEDANCE DEVICE WHICH IS OPERABLE BY A CONTROL SIGNAL TO ENERGISE THE COIL AND CHARGE THE CAPACITOR. THE SECOND MEANS INCLUDES A DISCHARGE CIRCUIT FOR THE CAPACITOR AND COMPRISES THE COIL AND A SECOND CONTROLLED IMPEDIANCE DEVICE WHICH OPERATES ONLY WHEN THE FIRST CONTROLLED IMPEDANCE DEVICE IS RENDERED INOPERATIVE. WHEN IT IS REQUIRED TO REDUCE THE ENERGISATION OF THE COIL, THE FIRST CONTROLLED IMPEDANCE DEVICE IS RENDERED INOPERATIVE WHEREUPON THE SECOND CONTROLLED IMPEDANCE DEVICE AUTOMATICALLY OPERATES TO DISCHARGE THE CAPACITOR THROUGH THE COIL TO PROVIDE THE REVERSE CURRENT FLOW THERETHROUGH.

Compatible EMI Filters

Abstract: A vexing problem in electromagnetic compatibility is the effective filtering of conducted interference from power-supply lines. Because of unavoidable and severe mismatch, conventional suppression filters operate only conditionally; such filters are often so large that they are omitted from the system. Three new classes of power-line filters without these limitations are described. They are active, truly lossy, and ruggedized ceramic filters, covering the frequency range from direct current to microwaves. Present filter test methods are shown to be misleading and are replaced by a rather simple realistic test. There is a set of filter classes that is rapidly growing in importance and, by necessity, is characterized by the absence of impedance matching. Without matching, all the elegant filter theories developed invalidate the very premise upon which they were based, and the theories are wholly inadequate and misleading. Such conditions exist for filters inserted into power lines; power wiring is contrasted with impedance-matched cabling that interconnects subsystems for irformation handling and for which conventional filtering is fully adequate. Suppression of conducted EMI (electromagnetic interference) constitutes an essential part of EMC (electromagnetic compatibility) and has, thus far, been frustrating and inadequate. Conventional EMI or RFI (radio-frequency interference) filters, because of interface mismatching are, in general, undependable. Another basic difference of power-line filters, as contrasted with information handling filters, is that they are strongly biased by the very power they have to pass. Three generic types of filters are described and discussed in some detail.

Electromagnetic interference measurement methodology, communication equipment.

Abstract: Issued as Monthly status report, nos. 1-12, Quarterly report, nos. 1-3, and Final report, Project no. A-1075

Measurements of the Attenuation of the Electric and Magnetic Fields at Points Close to the Source

Abstract: The problem of predicting the variation of the electric and magnetic field components as a function of radial distance at points relatively close to the source is of particular interest in electromagnetic compatibility investigations. The authors have recently had the opportunity to make experimental measurements of the rate of attenuation of electric and magnetic fields at points from 3 to 600 feet from the source at a number of different frequencies. The resulting data have application in RFI work as an aid for evaluating interference problems and estimating the effectiveness of radiation suppression measures.

EMI Data Reduction, Prediction, and Analysis Using Time-Shared Computers

Abstract: Today's complex electronic systems require that the Design Engineers pay particular attention to the side effects of Electromagnetic Interference (EMI) upon system operation. To assist the Design Engineer in considering these additional parameters, the Electromagnetic compatibility (EMC) Engineer must furnish useful tools to enable such considerations to be in the basic design. Through the use of the time-shared computer, which is available through a teleprinter terminal, the complexity and drudgery of EMI Data reduction, prediction, and analysis can be significantly reduced when suitable programs are available. This paper presents two typical programs and describes the major operations and operator-computer interplay. The first program describes the solution to a filtering problem and incorporates Fourier analysis, specification limits, desired values of L, C, and circuit values for source and load impedances. In addition to determining the filter insertion loss as a function of frequency, the program translates these requirements into a 50 ohm system to expedite the purchase of ready-made filters. The second program presented may be used in the reduction of EMI data resulting from broadband conducted interference testing using a current probe. The operator may elect several options during the progress of the program and is requested to enter data readings. Upon completion, the computer prints out a complete data sheet and a graph of the values (data readings plus current probe factors) and specification limits versus frequency. Tilt levels (values greater than the specification limit) are included in the data table.

Electromagnetic Compatibility Operational System (EMCOPS)

Abstract: A system has been developed to provide electromagnetic compatibility for military frequency usage throughout an extensive geographic area. This system employs a digital computer and an extensive data base of electromagnetic equipment parameters to perform real-time frequency usage analysis. Electromagnetic interference is identified and controlled by a subsystem that includes frequency-scanning surveillance receivers having their digital outputs linked to the computer and the system data base. Such functions as schedule planning, data acquisition, interference prediction, and documentation are performed by the system. Modular system design has allowed partial system operation while implementation is still in progress. This same modular property allows subsystem refinements to be implemented with a minimum of interfacing problems.

Measurement of Manmade Electromagnetic Radiations from a 200-Mile Orbit

Abstract: The study determined the feasibility of measuring electromagnetic radiations over the 0.1 to 15 GHz frequency range from a orbiting spacecraft. The primary objective was to define an experiment for an Apollo mission, although an unmanned space vehicle experiment is also considered. The study concludes that such an experiment is feasible and suggests an evolutionary series of experiments. Significant objectives of the first experiment are: (1) to measure RF as a function of earth location with -100 dbm receiver sensitivity, (2) enhance the over-all experiment with the astronaut by making decisions and performing real-time analysis of the experiment and of intentionally varied signals, (3) the experiment can be integrated into a mission depending on the spacecraft and other experiments, (4) extensive coverage of populated areas by orbit inclinations of 28 to 90 degrees, and (5) process and display of accumulated data by computers to the extent required by different users. The resulting data may find use in frequency allocation, equipment specifications, operational procedures, and interference maps that will be useful in site selection.