Analysis of Emission from Shielded PCB and Optimisation of Shield Parameters
Annie Sebastian, P. Salil, Bandaru Subbarao.," International Conference on Electromagnetic Interference & Compatibility (INCEMIC 2010)",Bangalore,November 25-26, 2010
Abstract: Electromagnetic shielding is employed to reduce the RF emission and to improve the immunity to RF noise for the electronic equipments. The performance of such shielding is determined by the shielding effectiveness. Metallic enclosures which are continuous can provide good results. But practical enclosures cannot be continuous and may have openings or apertures which negatively affect the shielding effectiveness. Such openings may be necessary for heat dissipation, I/O cable penetration, signalling and services. It is required to optimise the dimensions and the positions of the apertures as well as the RF sources ie. the PCB inside the enclosure to achieve minimum emission. In this paper the improvement of shielding effectiveness by optimizing various parameters like placement of apertures on the enclosure, dimensions of the aperture, position of the PCB inside the enclosure are studied. Numerical models of the enclosures are studied for various configurations and analysed for the emission using the mathematical tools and commercially available CAD tool-FEKO for EM simulation.
A Time Domain Pre-Compliance Conducted Emission Test System
E. Krishna Kishore, P. Salil, B. Subbarao,." International Conference on Electromagnetic Interference & Compatibility (INCEMIC 2010)",Bangalore,November 25-26, 2010
Abstract: Electromagnetic compatibility (EMC) compliance of electronic devices is one of the important issues that the developers encounter before the product release. This is a time consuming and expensive process. In the conventional, EMI test receivers, using swept frequency method, the time consumed for the measurement may be very long to be considered for iterations during the design. Another disadvantage in the swept frequency approach is that it cannot correctly determine the power spectrum of transient or pulsed emission. Also the developers rarely get opportunity to test the product as in most of the cases in-house test facility may not be available due to the cost constraints. In this paper, development of a low cost Time Domain EMI Emission Measurement (TDEEM) system is discussed.
Variation in Insertion Loss Characteristics of CM Choke due to External Influence
G. Mahesh, R. Parameswari, R. Vanitha, B. Subbarao,." International Conference on Electromagnetic Interference & Compatibility (INCEMIC 2010)",Bangalore,November 25-26, 2010
Abstract: For typical EMI filtering applications CM chokes are generally installed inside an enclosure. However the effectiveness of the CM choke reduces when installed inside an enclosure. It was analysed and found that the insertion loss of CM choke can vary significantly when tested in ideal condition in a lab/test bench and when the same CM choke is installed inside an equipment or enclosure. Various factors like stray electromagnetic field from external source, parasitic capacitance with enclosure etc. can contribute to variation in insertion loss characteristics. This paper analyses the effect of various metallic enclosures on insertion loss characteristics of CM choke. Insertion loss measurement results for a common mode choke with different metallic enclosures are presented in this paper. Attempt is also being made to simulate the insertion loss characteristics of CM choke along with enclosure in software and the simulated results are compared with experimental results.
Verification of ESD Generator with Different Co-axial Targets
G. Mahesh, G. Vincentraj, J. Thomas Vethamoni, B. Subbarao,." International Conference on Electromagnetic Interference & Compatibility (INCEMIC 2010)",Bangalore,November 25-26, 2010
Abstract: The ESD standard IEC 61000-4-2:1995, First edition has specified a ‘Pelligrini target’ with approximate bandwidth of 1 GHz which has to be used for verification of discharge current waveform. In order to avoid measurement discrepancies due to increasing bandwidth of measurement instrumentation the current version of ESD standard (IEC 61000-4-2:2008, Edition 2) has specified a ‘new target’ with 4 GHz bandwidth for waveform verification. The latest edition of IEC 61000-4-2 standard also calls for ESD current waveform verification using an oscilloscope with an analog bandwidth of 2 GHz or more. This paper discusses in detail about ESD current waveform verification procedure as per earlier and latest edition of IEC 61000-4-2 standard. Comparison results of ESD generator current waveform using ESD targets specified by earlier edition and present edition of IEC 61000-4-2 standard is also presented. Few guidelines to be followed for reducing the measurement errors during ESD calibration is also discussed.
Automation of Military Standard Electromagnetic Compatibility Tests
T.J. Sabarinath, P. Salil, B. Subbarao,." International Conference on Electromagnetic Interference & Compatibility (INCEMIC 2010)",Bangalore,November 25-26, 2010
Abstract: Conducted and Radiated emission Tests as per MIL-STD 461D,461E,461F are needed to be carried out on surface ship, submarine, aircraft, navy, army and ground subsystems/equipments involve making the test setup, calibration of measuring instruments, verification of test setup and performing the actual tests. A wide range of test frequencies are involved: 30 Hz to 100 kHz for conducted mode tests and 10 kHz to 18 GHz for radiated mode tests. Performing EMI tests in manual mode, sometime, may become tedious, time consuming and may have measurement inaccuracies. An automated EMC test system has been developed in-house to perform equipment level testing. This paper details the steps involved in the development of the automated EMC test system and different features of the test System.
Discussion on Issues with MIL 461E RS101 Testing
Senthil Kumar R.S , Suresh G , Subbarao B,." International Conference on Electromagnetic Interference & Compatibility (INCEMIC 2010)",Bangalore,November 25-26, 2010
Abstract: The MIL-STD-461E Standard requires magnetic field measurement in the low frequency range from 30 Hz - 100 kHz as per Test RS101. The test requires a 13cm loop Antenna which is associated with the following problems such as lesser field uniformity, higher manual involvement, higher uncertainty, increased time consumption, non uniform scanning etc. In this paper, efforts are made to understand these issues and suggestions are also made to reduce these issues.
Time & Quality Improvement of Radiated Emission Measurement Using Automation
M. Shakthi, J. Bharathidasan, P. Salil , B. Subbarao,." International Conference on Electromagnetic Interference & Compatibility (INCEMIC 2010)",Bangalore,November 25-26, 2010
Abstract: In many countries, electronic devices and systems are required to meet the Electromagnetic Compatibility (EMC) requirements based on different standards. The growing trend toward a global marketplace has compelled many manufacturers to place strong emphasis in EMC compliance. As the EMC test laboratories are capital intensive investments, small and medium scale industries prefer to depend on third party test labs for product testing / certifications. This demands EMC Test Laboratories to demonstrate some measure of assurance that the product is tested as per the applicable test criteria. Hence the Quality of measurement is must. It is found that one of the most request tests is the Radiated Emission (RE) measurements, with often a back logoff test request in queue. Automation of the Radiated Emission measurement has been carried out which, reduces time, increases repeatability and thereby improving the quality of measurement.
Quality Improvement in Antennae Calibration via Facility Automation
P. Salil, B. Subbarao,." International Conference on Electromagnetic Interference & Compatibility (INCEMIC 2010)",Bangalore,November 25-26, 2010
Abstract: Antenna Factor (AF) is one of the most widely used device specification in the EMC area. Antenna factor reflects the use of an antenna as a field measuring device. For the accurate measurements, it is required that the antennae are calibrated accurately. Even though the antennae calibration is relatively straight forward, there are many influencing factors that make the results inaccurate. In this paper, the improvement in accuracy as well as other aspects of an automated antennae calibration facility is discussed. The antennae calibration procedure based on the standard site method given in ANSI C63.5-2004 is followed.
Protection Techniques against the High Power Electromagnetic Pulse
Salil P., Subbarao B., "Seminar on Future Wars, Use of EM weapons, Impact and Counter measures", Army Centre for Electromagnetics, Mhow, UP, February 2-3, 2009
Abstract: Developments in the area of High Power Electromagnetic Pulse generation techniques and High Power Microwave Technology have grown to an extent that the defence services are able to use such sources to damage enemy electronics in Strategic and Tactical Information Warfare. In today’s scenario where much of the victory in warfare is decided by the access to quick information, the protection of the information processing / communication systems are very critical. The traditional methodology for verifying the capability of defence equipment for the immunity to the electromagnetic energy is confined to the immunity tests defined by the MIL 461 Series Standards. The tests as per this standard limit the test level by few volts for conducted or volts per meter for radiated immunity tests, which make the compliance to these standards irrelevant in comparison with the EMP sources / weapons. Such weapons generate a very short, intense energy pulse producing a transient surge of thousands of volts, which can damage non protected semiconductor devices. Also the frequencies generated can extend from very low frequency to the range of tens of Gigahertz, making it possible for penetration even through minute gaps in the shielding. A better awareness and understanding about such weapons helps in preparedness against any such attack. In this paper the effects and the various protection techniques against the EMP weapons are discussed.
The Need for Review of EMC Emission Standard
G. Vincentraj, B. Subbarao, R. Sivaramakrishnan,International Conference on Electromagnetic Interference and Compatibility, Bangalore, November 26-27, 2008
Abstract: Generally the Radiated Emission measurement is performed in the frequency range of 30 MHz to 1000 MHz as per the commercial EMC Standards. The Conducted Emission measurement is done in the frequency range of 150 kHz to 30 MHz. Whereas in the Military Standard the Conducted Emission measurement frequency range is from 9 kHz to 50 MHz and in the automotive standard up to 108 MHz. This paper proposes the frequency range of measurement for Conducted Emission from 150 kHz to 108 MHz and for Radiated Emission from 100 MHz to 1000 MHz. This paper also discusses the advantages of choosing the frequency band from 100 MHz to 1000 MHz for Radiated Emission measurement and additional issues that need to be addressed due to the change in the measurement frequency band. » read more
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