Identifying emission sources for EMC improvements - Analyzing the origin and propagation of electromagnetic emissions from an electronic device

Abstract

Electromagnetic compatibility (EMC) is a vital part of product development, and understanding the sources and causes of the emissions can facilitate tremendously in reaching compliance requirements and reduce the work needed for troubleshooting. At Axis Communications, where this thesis has taken place, the knowledge of EMC is an important part of their work and they aspire to improve further.
This thesis aims to create a test setup and method to investigate one common interference source that can create challenges in the development of new products. Using the same method to identify and find solutions to common interferences facilitates the development process and reduces the need for EMI (Electromagnetic interference) troubleshooting. In the project, the electronics of one of Axis' cameras were investigated and tested through A/B tests, where new tests are formed by analyzing the results from the previously performed tests. The different types of testing that were conducted in the project were measuring the emissions in an anechoic chamber with varying changes made to the device under test, 'sniffing' with near field probes on the printed circuit boards (PCBs), and determining the resonant frequencies for cables with a network analyzer.
The project results include identifying the source of one clock signal and its harmonics and characterizing the emissions from it depending on PCB placement and the surrounding material.
The impact the slip ring made on the emissions was investigated and it was deemed not to affect them in any significant way.
The investigation of the anechoic chamber and how the choice of cables used outside it could affect the zoning and cancel the shielding of it.

Popular Abstract

Tackling electronic noise - a systematic approach.

Controlling your lights from your phone sounds cool until it accidentally controls your neighbours new smart-dishwasher. When electronics can freely emit signals without limits big problems can arise. To avoid these unwanted miscommunications between electronic devices we need to control the signals sent out by them. These unwanted signals are called Electromagnetic emissions and when they affect other electronics it is called Electromagnetic interference (EMI).
The purpose of this thesis has been to investigate common electromagnetic emissions found in circuits and other electronic components to help reduce emissions before a product is even assembled. Many electronic components and subsystems are not specific to only one product. By identifying emissions early in the building process, solutions can be found directly, avoiding unnecessary troubleshooting for many products. Throughout this thesis, I aimed to acquire both knowledge about what could cause emissions in various components as well as create a more straightforward testing plan for this. The thesis was conducted with Axis Communications.

Axis Communications produces a variety of products related to surveillance and security so naturally this includes cameras. I conducted my thesis on a camera to identify issues with the camera-components. The overall goal was to create a testing-procedure to make identifying emissions simpler. My theory was that rather than looking at the whole product, it would be more beneficial to start with the components.

The thesis involved doing a lot of measuring and testing in an anechoic chamber with an antenna and EMI test receiver as well as measuring the near field with near field probes. An anechoic chamber is a chamber that is shielded from all electromagnetic emissions of its surroundings and has a special material on the inside that disables the electromagnetic waves from reflecting on the walls, so no electromagnetic echo will appear.

The method I developed is based on forming comparative A/B tests. A/B tests are a form of comparative testing where two or more measurements can be compared against each other and only one change is made between them. This way the effects of this changed parameter can be seen and the understanding of how the emissions work can increase. In my specific application, this was done by analyzing the previous test result and the electronics in the device to learn about what and how is causing the radiation.

With the testing procedure described above, the emissions were measured from the entire camera as well as the electronics on their own. What this showed is that the surrounding materials, such as the metal chassis and motors affected the emissions. By measuring the EMI from only the components it was possible to determine that the materials around the electronics can have both a dampening and amplifying effect on the emissions. As the components may be used in a variety of products whether the emissions are dampened or amplified can vary and it is therefore important to combat the emissions at the source.

• author: Gustafsson, Ida
• supervisor: Johan Nilsson; Johan Gran; Thomas Lawton
• organization: Department of Biomedical Engineering
• alternative title: Identifiering av emissionskällor för EMC-förbättringar - Analys av ursprung och fortplantning av elektromagnetiska emissioner från en elektronisk enhet
• course: BMEM05 20241
• year: 2024
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: EMC, EMI
• language: English
• id: 9150662
• date added to LUP: 2024-04-15 09:06:56
• date last changed: 2024-04-15 09:06:56