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Progress In Electromagnetics Research Symposium Proceedings, Stockholm, Sweden, Aug. 12-15, 2013 1267

The Design and Implementation of an EMC Pre-compliance Board

F. R. L. Silva1, L. R. Ribeiro1, L. P. Dias1, W. J. Santos1, C. E. Capovilla2, and H. X. Araujo1

1Universidade Federal de Sao Joao Del Rei — UFSJ, Ouro Branco, Brazil2Universidade Federal do ABC — UFABC, Santo Andre, Brazil

Abstract— In this work, the EMC — Electromagnetic Compatibility of Integrated Circuits,electronic boards and home appliances is deal with the use of a conducted emission technique. Ingeneral, as the IC the major responsible of unintentional emissions and coupling, some specificpre-compliance setup tests are employed to analyze these detrimental effects to the system as awhole. Therefore, an EMC Pre-Compliance Board — EPCB was designed and built to operatefrom 150 KHz to 30 MHz. Additional techniques were used to improve the EPCB in terms of frequency range and performance. Simulated and experimental results are compared to validatethe EPCB test setup.

1. INTRODUCTION

The necessity to control the electromagnetic emissions and interference between circuits and elec-tronic devices becomes a crucial point to assure its correct operation inside an electromagnetic en-vironment. Some approaches were designed to support the pre-compliance tests (EMC/EMI/EMS)setups, which are not designed to replace the well-known compliance equipments (anechoic cham-ber, stirring chamber, blue test chamber, etc.) but, it gives a previously information about thedevice behavior [1]. All of them have consolidated standards and regulations.

The electrical circuit of any electronic device produces some kind of noise, which can reachlevels of power that interfere in undesired ways on the operation of the equipment around and theenvironment as a whole. Each device generates a characteristic noise, due to its electrical circuit [2].Depending on the electromagnetic emission of these noises, other electronic devices can then receivethe interference by a path of radiation or, much less frequently a direct electrical connection.

The analysis of conducted emission aims to measure how much electromagnetic radiation (noise)is conducted in an electronic equipment to the grid by the power cord. Such issuance may not exceed

the established standards [3], so that the overcoming of the imposed limit causes interference inthe operation of other devices that are connected on the same network.In this context, the EPCB test setup will be used between the power cord of the device un-

der test and the power outlet, to verify if the DUT meets the standards of conducted emission.The frequency range of the implemented board starts from 150 KHz to 30 MHz. Simulated andexperimental results are compared to validate the EPCB test setup.

2. EMC CONDUCTED METHOD

Since the mid-90s every electronic device must be submitted to stricter EMC measurement, andtheir entries in the market are directly related to it responses on these test. Although problemsrelated to interference during the Second War, only in the late 70s that the problems related to EMCbecame of public knowledge in general due to the problems presented by television, communicationequipment, audio and video displays, among many other applications [4].

By definition, electromagnetic interference — EMI is the process in which electromagnetic en-ergy is transmitted from one electronic device to another via radiated or conducted emission orboth. On the other hand, the electromagnetic susceptibility — EMS deals with devices sensitiveto interference from other devices. Thus, the EMC tests usually comprise both EMI and EMSmeasurement of the same electronic device. In Fig. 1 is shown the coverage of the electromagneticcompatibility.

Therefore, several EMC tests platforms were designed to evaluate the performance of electroniccircuits and devices aimed at preventing problems related to interference or immunity within anelectromagnetic environment. Among the most common and robust EMC platform, is the AnechoicChamber [5], which for several years has been the main method of evaluating the electromagneticbehavior of antennas, electronic devices, vehicles and even airplanes. However, the high valuerequired for their construction and maintenance, and the complexity of its operating system, makesinfeasible its acquisition for the analysis of small electronic devices. Therefore, other methods [5, 6]

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1268 PIERS Proceedings, Stockholm, Sweden, Aug. 12–15, 2013

Figure 1: Electromagnetic compatibility subdivided into EMI and EMS measurements [2].

less complex and costly show good results related to the interference and immunity analysis knownas pre-compliance test.

Different approaches assist the pre-compliance test, which are governed by their own standards

and rules [7]. These setups include the TEM/GTEM cells, magnetic loop, magnetic probe, Work-bench Faraday Cage, OATS — Open Area Test Site, 1/150 Ω conducted, LISN — Line ImpedanceStabilization Network, among others.

The pre-compliance setup tests, at the level of electronic systems are defined by the standardsCISPR 25/2002 (special international committee on radio interference) for spurious emissions, andthe ISO-11452 for interference susceptibility measurements. Thus, two major standards have beendefined, with a first one for radiated and conducted emission and the second one for immunity RFtest.

By definition, the conducted interference is that in which occurs undesirable transfer of electro-magnetic energy along a conductor through disturbances between the phase line and the groundpower supply, and is governed by the standard IEC 61967-4. There are several tools and method-ologies to perform conducted tests, and the frequency range normally used is 150 KHz–30 MHz,except in military applications that eventually require the extension band.

The most common method used for this type of analysis is the LISN, also known by AMN —Artificial Mains Network, which works through the AC power supply of the device to be analyzed.In spite of the minimum frequency of the conducted emission tests is normally around 150 KHz, bythe power switching held by the LISN is possible to achieve a minimum frequencies around 9 kHz.The advantages of using the LISN in conducted tests are mainly related to the fact that it provideselectromagnetic insulation against the external environment and characterize the impedance of theDUT — device under test. However, its cost may be a limiting factor.

Other method widely used in performing conducted interferences measurements is the 1/150 Ω,where is possible to measure the noise current in each driven pin of the DUT. The basic modelconsists of the presence of a low value resistance in series with the output pin of the DUT. Therefore,it is possible to measure the voltage across the known resistor and then determine the noise current.Based on the fact that most IC emission problems arise through the noise that is carried out bythe pins of the IC, this method presents itself as a good indicator. However, for each DUT and

application the equivalent circuit must be adapted and adjusted.

3. EMC PRE-COMPLIANCE BOARD — EPCB

To evaluate the conducted emission provided by a laptop, an electromagnetic compatibility pre-compliance board using resistors, capacitors and inductors was designed and built. The schematicof the designed circuit is shown in Fig. 2. The series inductance avoids that the noise coming fromthe device under test becomes into the grid, being directed to the 1 KΩ resistor on which the mea-surement is made using the spectrum analyzer. Any present noises on the line are misappropriatedby the 1 µ F capacitor placed in parallel with the network, thereby not affecting the measurement.

To perform the simulations, the Multisim Software was employed. The board was designed tooperate at 127 V and 60 Hz, the classical Brazilian standard. To obtain the impedance variationof the circuit as a function of the frequency, the AC analyses and the equivalent impedance wereneeded. In Fig. 3, is shown the EPCB unconnected and connected to a DUT and its impedance

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Progress In Electromagnetics Research Symposium Proceedings, Stockholm, Sweden, Aug. 12-15, 2013 1269

Figure 2: EPCB schematic.

(a) (b)

(c)

Figure 3: (a) Unconnected to the DUT; (b) connected to the DUT; (c) characteristic impedance of theEPCB.

Figure 4: Conducted emission test setup using an EPCB.

variation as a function of the frequency which tends to 50 Ω.The test setup, as shown in Fig. 4, was performed in accordance to CISPR and FCC — Federal

Communications Commission, agency in charge of standardization of radio communications andcable in the U.S. The test equipment used was a BK Precision Series 2650A spectrum analyzer,a certified FCC class B laptop, which served as the DUT and the EPCB. In Fig. 5, is shown theconducted emission scan of the fully configured, certified, class B laptop. To compare the responseprovided by the EPCB, a measurement with a commercial LISN was also done. Both results arecompared to the CISPR and FCC standards. From the obtained results, is possible to observe thegood agreement of this low cost pre-compliance test. As the laptop is certified, it was expected thatthe radiated emission levels must satisfied the standards. However, there are resonances around30 MHz, which can be caused by disturbances, provided by battery charger, connections betweenthe motherboard and peripherals devices or even due to the heating. Meanwhile, is important to

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emphasize that these resonances levels are minimal, and could also be inserted by the test platform.

Figure 5: Measurement results of a conducted emission for a certified Class B laptop.

4. CONCLUSIONS

The voltage and current in distribution lines are often corrupted by transient, distortions and otherdisorders, that come from natural sources such as lightning and also by the operation of electricaland electronic devices. These interferences are conducted over long distances and then coupled toother equipments connected to the grid.

Therefore, in this work, an EMC Pre-Compliance Board — EPCB was designed and built tooperate from 150 KHz to 30 MHz. It was shown the development of the proposed device since thedesign, simulations and experimental measurements. To validate the constructed board, it wasused a commercial LISN, working at the same frequency range. The analysis of a certified class B

laptop was also done performed in accordance to CISPR and FCC standards. Thereby, from theobtained results the EPCB test setup was clearly validate.

REFERENCES

1. Montrose, M. I. and E. M. Nakauchi, Testing for EMC Compliance , Wiley Interscience, NewYork, 2004.

2. Dhia, S. B., M. Ramdani, and E. Sicard, Electromagnetic Compatibility of Integrated Circuits:Techniques for Low Emission and Susceptibility , Springer, New York, 2006.

3. Paul, C. R., Introduction to Electromagnetic Compatibility , Wiley Series in Microwave andOptical Engineering, 1992.

4. “Electromagnetic compatibility (EMC) — Part 4: Testing and measurement techniques — Sec-tion 3: Radiated, radio-frequency, electromagnetic field immunity test,” International StandardCEI/IEC 1000-4-3, Geneva, February 1995.

5. Clay, S., “Improving the correlation between OATS, RF Anechoic room and GTEM radi-ated emissions measurements for directional radiators at frequencies between approximately150 MHz and 10 GHz,” IEEE International Symposium on Electromagnetic Compatibility ,Vol. 2, 1119–1124, Denver, USA, August 24–28, 1998.

6. De Araujo, H. X. and L. C. Kretly, “EMC pre-compliance test of RFIC and RF systems usinga laboratory GTEM chamber,” PIERS Proceedings , 896–900, Moscow, Russia, August 19–23,2012.

7. Hamid, R., M. Cetintas, and E. H. Karacadag, “EMC Test Facilities at UME,” IEEE Inter-national Symposium on Electromagnetic Compatibility, EMC’03 , 2003.