Askeri cihazlarda bağlantı yollu elektromanyetik girişim bastırma çalışması = Electromagnetic noise suppression study with connection path in military devices

Abstract

Bu tez çalışmasında, MIL-STD-461 G standartı doğrultusunda askeri cihazlar üzerinden elektromanyetik girişim (EMI) ve elektromanyetik uyumluluk (EMC) konuları üzerine bir inceleme yapılmıştır. EMI, bir cihazın çalışırken ortamda bulunan diğer cihazların çalışmasını etkileyebilecek elektromanyetik sinyallerin neden olduğu sorunlardır. EMC ise farklı cihaz veya sistemlerin aynı ortamda birlikte ve EMI olmadan çalışabilme yeteneklerini ifade eder. Askeri standartta emsiyon testleri iletilen emisyon (CE) ve yayılan emisyon (RE) olmak üzere iki kısma ayrılmaktadır. Bu tez çalışmasında CE testlerinden CE102 testi incelenmiştir. CE102, özellikle farklı sistemlerde EMC testi gerekliliklerini özetleyen askeri bir standart olan MIL-STD-461'in bir alt bölümüdür. CE102, tipik olarak 10 kHz ila 10 MHz frekans aralığında, güç hatlarına ve kablolara bağlanan iletilen emisyonların değerlendirilmesine odaklanır. Bu çalışmada askeri standartta belirtilen test bileşenleri ve test düzeneği standarta uygun şekilde kurulmuş ve ölçümler alınmıştır. Yapılan çalışmalarda farklı iki askeri cihazın yaymış olduğu elektromanyetik gürültülerin, frekans değeri ve gürültünün büyüklüğüne bağlı olarak gürültü seviyelerini azaltma yöntemleri incelenmiştir. Bu tez çalışmasında, laboratuvar ortamında uygulamayla elde edilen test sonuçları paylaşılmış ve sonuçlar hakkında değerlendirmeler yapılmıştır. Gürültü seviyelerine uygun müdahalede bulunmak için öncelikle gürültünün hangi türden (Ortak mod (OM) veya Fark modu (FM)) yayıldığını tespit etmek gerekmektedir. Gürültünün türüne göre farklı EMI filtreler tasarlanıp kullanılabilmektedir. Bu çalışmada gürültü seviyesini bastırmak için farklı tip ve boyutlarda kapasitör, bobin, ortak mod bobini, nüve ve filtreler kullanılmıştır. Bu eklemelerin yanı sıra diğer gürültü bastırma yöntemleri (topraklama, Faraday kafesi, kabloların ekranlanması) de uygulanarak iki farklı askeri proje üzerindeki etkileri paylaşılmıştır. Uygulamada kullanılan iki askeri cihazın çalışma mantığı ve çalışma gerilimleri farklıdır. Cihazların çalışma gerilimlerinin farklı olması sebebiyle standartta verilen sınır değerlerde esneme yapılarak ölçümler alınmıştır. CE102 testinin limitleri, cihazın tipine, kullanım amacına ve uyulması gereken askeri veya endüstriyel standartlara göre değişmektedir. Bu testlerde kullanılan limitler, cihazın yaydığı gürültünün tespit edilen sınırlar içinde kalmasını sağlamak amacıyla belirlenir. Bu tez çalışmasında farklı limit değerlerine sahip cihazların, ilk ölçümlerdeki sınır seviyesinin üzerindeki değerleri, kabul edilen sınır seviyelerine indirilmiştir. Gürültü seviyesini düşürmek için yapılan her bir değişikliğin cihazlara olumlu veya olumsuz etkileri ayrı ayrı ölçülerek çalışmaya eklenmiştir. Bu çalışmanın hedefi, farklı standartlarda emisyon testleri yapacak araştırmacılara yardımcı olmaktır.

Parallel to technological developments, devices and systems that emit electromagnetic energy are increasing rapidly, and electromagnetic interference (EMI) problems arise. The importance of studies on the solution of these problems has been understood. Solving EMI problems is a critical step in improving the reliability and performance of devices, protecting communication and meeting legal requirements. In this thesis, a research study was conducted on EMI and electromagnetic compatibility (EMC) issues over military devices in accordance with MIL-STD-461 G standard. EMI is the problems caused by electromagnetic signals that can affect the operation of other devices in the environment while a device is operating. EMC refers to the ability of different devices or systems to operate together in the same environment and without EMI. In military standards, emissions tests are divided into two parts, conducted emission (CE) and radiated emission (RE). CE testing is a type of EMC test performed on electronic devices to measure the level of unwanted electromagnetic interference they generate and emit through their power and signal cables. CE102, specifically, is a subsection of MIL-STD-461, a military standard that outlines requirements for EMC testing in different systems. In this thesis study, the CE102 test was examined. CE102 focuses on the assessment of conducted emissions that are coupled onto power lines and cables, typically in the frequency range of 10 kHz to 10 MHz. This testing ensures that electronic equipment does not generate excessive electromagnetic interference that could disrupt the operation of other nearby device or systems. The purpose of CE102 testing is to ensure that devices meet EMC standards and operate reliably without causing interference to other equipment. During a CE test, the device under test (DUT) is connected to a test setup that includes power and signal cables. The DUT is subjected to various operating conditions while its emissions are measured using specialized test equipment. The emissions are typically measured across a range of frequencies, with specific limits defined by EMC standards. The test components and test setup specified in the military standard were set up in accordance with the standard and measurements were taken. In the studies, the methods of reducing the noise levels of electromagnetic noise emitted by two different military devices, depending on the frequency value and the size of the noise, were examined. In this thesis, the test results obtained with the application in the laboratory environment were shared and the results were evaluated. There are different methods to reduce the noise level. These are shielding, grounding, filtering, isolation, cabling and wiring, EMC compliant design. In this study, different types and sizes of capacitance, coil, common mode choke, core and filters are used to reduce the noise level. In addition to these studies, other noise reducing methods (such as grounding, Faraday cage, shielding of cables) were applied and xxii their effects on two different military projects were shared. The operating voltages of the devices are 28 V DC and 220 V AC. Operating voltages are the most important factor to determine the limit values of the devices. Therefore, while selecting the limit value, the operating voltage of the device was checked and the limit value was selected from the standard. Basic curve limit is selected for 28 V DC. For 220 V, basic curve + 9 dB is selected. The pass or fail ciriterion depends on for the DUT specified limit. Once the limit value is determined, it is necessary to determine which type of noise (Common mode (CM) or Differential mode (DM)) is emitted in order to intervene appropriately in the noise levels. CM refers to the situation where unwanted noise or interference is present on both signal lines with respect to a common reference point, typically ground. In other words, the noise is superimposed on both signal lines in the same direction. DM refers to the desired signal that is present between two signal lines while the unwanted noise or interference is present in the opposite direction on those lines. In other words, it's the difference between the signals on the two lines. Different EMI filters can be designed and used according to the type of noise. When using filters, ready-made filters can be used or special filters can be designed to suit the noise level. EMI filters work by attenuating or blocking unwanted electromagnetic signal within a specific frequency range while allowing desired signals to pass through. They are commonly used in applications such as power supplies, electronic equipment, communication systems, and other devices that require reliable operation and compliance with EMC standards. EMI filters can be designed for various applications, such as conducted EMI filtering or radiated EMI filtering. These filters typically consist of passive components such as capacitors, inductors, and resistors arranged in specific configurations to achieve the desired level of noise suppression. The design and placement of EMI filters are critical in achieving the desired level of electromagnetic compatibility and interference suppression for electrical and electronic systems. Proper placement can help minimize interference both from within the system (conducted and radiated emissions) and from external sources. Different systems have different EMI characteristics and filter placement must be tailored to the specific application. This is particularly important in sensitive applications where interference could disrupt the proper operation of equipment, communications systems, or safety-critical systems. A customized approach helps filters address specific interference issues the system will encounter. The operating structure and operating voltage values of the two military devices used in this study are different. Since the operating voltages of the devices are different, measurements were taken by stretching the limit value given in the standard. The limit of the CE102 test is determined according to the type of device, the area of use and the military or industrial standards that must be complied with. These standards provide guidance on emission limits for different frequency ranges and scenarios, ensuring that military components can operate effectively without causing or succumbing to electromagnetic interference. It's important to consult the specific EMC standards applicable to the country or military organization for accurate information on emission limits for military components. The limits used in these tests are determined to ensure that the noise emitted by the device stays within certain limits. The steps specified in the standard must be taken into account in order to measure the noise level accurately, to ensure proper operation of the test apparatus, and to intervene appropriately in the noise level. The standard states that an attenuator should be used to avoid affecting the measurement receiver. The 20 dB attenuator and the pulse limiter is necessary for protecting the EMI receiver, it is also xxiii providing a better impedance between the signal output of the LISN and the input of the EMI receiver. This amount of attenuation is added back to the noise amplitude in the data recorder by the measurement program. The accuracy of the test setup must be ensured before measurements are taken. Applies a signal level to the LISN's power output that is at least 6 dB below the 10 kHz, 100 kHz, 2 MHz, and 10 MHz limit. An oscilloscope is used to calibrate the signal level at 10 kHz and 100 kHz. At 2 MHz and 10 MHz, a calibrated output level is applied directly from the 50Ω signal generator. Normal scan is performed for each frequency with the EMI Receiver and verified that the applied level is within ±3 dB. If there is a deviation of more than ± 3 dB in the measured signal levels, the test is not continued and the error in the system must be resolved. When the TAC power supply is cut off and all other auxiliary devices are turned on, the measured ambient electromagnetic level must be 6 dB below the safety margin of the relevant limit values. If a sinusoidal emission signal is considered to be at the full limit value, the ambient level will be 6 dB below the limit value and the measured value will be approximately 3 dB above the limit value. In this case, it remains within the measurement system tolerance. The margin of safety was taken into account when making measurements. Once all the above-mentioned conditions are met, appropriate measurements can be taken. In this thesis, it was mentioned that a test device in accordance with MIL-STD-461 G should be established. Afterwards, by following the steps specified in the standard, bandwidth, scanning time, measurement receiver and detector selection and ensuring standard conditions are explained. The sources of noise in the measurements taken and the interventions to be made are explained. The results of the devices with different limit values above the limit level in the first measurements were reduced to the accepted limit levels. Different types and sizes of capacitors, CMC and filters were used in the measurements. The positive or negative effects of each change made to reduce the noise level were evaluated and added to the study by measuring separately. The circuit diagram of the components that yielded the best results was given and added to the internal structure of the device. This study aims to help researchers that will work on emission tests at different standards.