The Best Value in Electronic Test & Measurement

Pre-compliance Basics How to get through compliance quickly

What is EMC Testing? EMC = Electromagnetic Compatibility Moving electrons create electromagnetic waves For an intentional radiator (radios, WiFi, etc.) these are desirable.. But.. Unintentional radiators: The waves interfere with other intentional radiators or cause issues (jamming, lock up, failure).. This undesirable radiation is known as Electromagnetic Interference (EMI) Governments regulate the amount of EMI allowed (RF or other) Guidelines in the US are created and enforced by the FCC (Federal Communications Commission) Compliance is self-determined… but the testing can be complex. End result – you have to rely on special test houses (Compliance Labs) to perform the required testing.

Basic EMC tests Radiated Emissions – How much RF is flying off of a product Conducted Emissions – How much RF is sent back down the power line Susceptibility - How much RF can your product take before failure

Radiated Emissions Must isolate the DUT from the environmental RF Open air or special chamber (anechoic or semi-anechoic) = $$ Physical and electrical test setup is critical Averages $2000/day.. for testing. Consultation can cost more

Radiated Emissions Basic Setup

Radiated Emissions: Pre-compliance Difficult without a chamber, but possible Consistent, repeatable, and well understood environmental RF (background scans) Physical layout should not change (people, equipment, desks, etc..) Reflections (Hot/cold spots) should be understood Still relative measurements.. So, you can get meaningful data.. Use a fixed physical layout (measured distances and angles), pictures of the tests, etc.. Perform an environmental RF test immediately before and after DUT testing (DUT off) If you have a failed test report, you can use this to help “key in” on specific frequencies

Near field probes Near field = close proximity measurements Far field measurement antennas ~ 1 m or more away from DUT Near field ~ an inch or two Magnetic (H) and Electric (E) field probe types Can ignore environmental effects due to weak coupling Simple setup Fixturing can minimize variations and make better relative measurements Can use with a failed report to help find root cause of issues

Near field probes

Current clamp Cabling can radiate and cause failures.. Especially poorly shielded cables Can make relative measurements using a current clamp

Conducted Emissions Measures DUT energy directed towards the power grid Interference on power lines causes AM radio interference Much more repeatable than radiated.. And easier

Susceptibility Irradiate DUT and check performance Must shield to prevent exceeding FCC regulations for unlicensed transmissions Can use near field probes to inject signals onto boards and traces

Tools Spectrum analyzer – The “eyes” of the EMC Engineer Oscilloscope with FFT Sequencing software Near field probes Antennas (rabbit ears and bowties can be useful in some situations) Current clamps Aluminum foil Conductive tape Line Impedance Stabilization Network (LISN) and transient limiter RF Source with AM modulation capability probe can easily find leaks AM Radio (can be used to troubleshoot radiated issues)

SIGLENT Tools SIGLENT SSA3021X/32X – 2.1 GHz/3.2 GHz Spectrum analyzer (Start at $1395) SIGLENT SVA1015X – Spectrum and vector network analyzer (Start at $1395) EasySpectrum software (free) SIGLENT SDS series of scopes (Start at $299) SRF5030 and SRF5030T near field probes More to come…

Common failure root causes Harmonics- What is the rise time of digital signals within your enclosure? Faster rise times = higher frequency harmonics = potential for trouble Shield terminations on connectors – Are they really shielded 360°? Small common mode currents (a few uA) can radiate.. And will find an antenna LCDs – Rarely shielded well and have high data rates Unintentional antennas (cutouts/holes are physically identical to “solid” antennas) Splits in ground planes .. time varying currents follow path of least impedance, not just resistance.. Control current return paths, or the electrons will find their own way “home” Enclosure shielding/gasketing – Nearfield probe can easily find leaks

Resources Application Notes: Books: Pre-compliance basics: https://www.siglentamerica.com/application-note/electromagnetic-compliance-pre-compliance-test-basics/ Pre-compliance Near Field: https://www.siglentamerica.com/application-note/electromagnetic-compliance-troubleshooting-near-field-current-probes/ Pre-compliance Conducted Emissions: https://www.siglentamerica.com/application-note/electromagnetic-compliance-pre-compliance-conducted-emissions-testing/ EasySpectrum software: https://www.siglentamerica.com/operating-tip/getting-started-easyspectrum-software/ Books: EMI Troubleshooting Cookbook: Andre’ and Wyatt Electromagnetic Compatibility Engineering: Ott

Resources, con’t Useful sites: FCC subpart 15 limits: www.fcc.gov The EMC Blog: https://www.edn.com/electronics-blogs/4376432/The-EMC-Blog Ken Wyatt: https://www.emc-seminars.com/ Doug Smith: http://emcesd.com/bcsem_emcweek.htm IEEE EMC Society: http://www.emcs.org/

SIGLENT—The Best Value in Electronic Test & Measurement Thank You SIGLENT—The Best Value in Electronic Test & Measurement Contact Info Company Address www.siglentamerica.com Email：info@siglent.com Tel：440-398-5800 6557 Cochran Rd Solon, OH 44139