EMI/EMC Glossary

Basic Concepts

Electromagnetic Interference (EMI)전자파 간섭 (EMI)

Degradation of a device’s performance caused by an electromagnetic disturbance, or the emission that causes it.

Electromagnetic Compatibility (EMC)전자파 적합성 (EMC)

The ability of equipment to operate in its electromagnetic environment without causing unacceptable disturbance to anything else.

Immunity내성 (면역)

The ability of a device to operate without degradation in the presence of an electromagnetic disturbance, judged in tests against performance criteria A, B, C.

Emission방출

Electromagnetic energy a device sends out by conduction or radiation; standards set permitted limits.

Susceptibility감수성

The tendency of a device to be degraded by disturbance; the counterpart of immunity, mostly used in military standards.

Conducted Emission전도 방출

Electromagnetic energy leaving along conductors such as power and signal lines, typically measured from 150 kHz to 30 MHz with a LISN.

Radiated Emission방사 방출

Electromagnetic energy radiated into space, normally measured above 30 MHz with an antenna.

Common Mode (CM)공통모드 (CM)

Current component flowing in the same direction on both conductors. Cables act as antennas for it, making it the main cause of radiated emissions.

Differential Mode (DM)차동모드 (DM)

The normal signal-current component flowing in opposite directions on two conductors; radiation is small when the loop area is small.

Near Field근거리장

Region close to the source where the E/H ratio differs from a plane wave; may be electric-field or magnetic-field dominated.

Far Field원거리장

Region where the wave is regarded as a plane wave: E/H is about 377 Ω and the field falls inversely with distance.

Harmonic고조파

A frequency component at an integer multiple of the fundamental. Harmonics of clocks and switching supplies are classic emission failures.

Spurious Emission스퓨리어스 방출

Unwanted emission outside the intended signal band, such as harmonics and intermodulation products.

Intermodulation상호변조

Mixing of two or more signals in a nonlinear element, producing sum and difference frequency components.

Rise Time상승시간

Time for a signal to go from 10 % to 90 % of its final value. A shorter rise time carries more high-frequency content.

Crosstalk크로스토크

Signal leaking between adjacent traces through capacitive and inductive coupling.

Resonance공진

Strong amplification of response at a frequency set by L and C (or a structure’s length). Cable and slot resonances increase emissions.

Q FactorQ 값

A measure of how sharp a resonance is; the higher the Q, the taller and narrower the peak.

Impedance Matching임피던스 정합

Matching source, line and load impedances to reduce reflection; poor matching raises the VSWR.

Transfer Impedance전달 임피던스

Ratio of induced voltage to current for a shielded cable or a current probe; lower values mean better shielding.

Skin Effect표피 효과

High-frequency current flowing mostly near the conductor surface; skin depth decreases as frequency rises.

Return Path귀환 경로

Path by which signal current returns to the source. At high frequency the plane directly under the trace is the lowest-inductance path.

Ground Bounce접지 바운스

Fluctuation of ground potential across ground inductance when many outputs switch at once.

Measurement & Instruments

dBm

Absolute power level referenced to 1 mW (0 dBm).

dBµV

Voltage level referenced to 1 µV. At 50 Ω, dBµV = dBm + 107.

dBµV/m

Field-strength level referenced to 1 µV/m; the unit of radiated-emission limits.

Antenna Factor (AF)안테나 팩터 (AF)

Coefficient (dB/m) converting receiver voltage to incident field: E = V + AF.

LISN / AMN

Line impedance stabilisation network / artificial mains network: gives a defined impedance and isolates mains noise during conducted-emission measurement.

Impedance Stabilisation Network (ISN)ISN (임피던스 안정화 회로망)

Network used to measure asymmetric (common-mode) conducted emissions on telecom and signal ports.

Coupling/Decoupling Network (CDN)CDN (결합·분리 회로망)

Network that couples the disturbance onto a cable and decouples auxiliary equipment in conducted-immunity tests.

Resolution Bandwidth (RBW)분해능 대역폭 (RBW)

Width of the measurement filter. Reducing it lowers the noise floor but lengthens the scan.

Video Bandwidth (VBW)비디오 대역폭 (VBW)

Post-detection filter bandwidth; lowering it smooths out noise variations.

Quasi-Peak Detector (QP)준첨두 검출기 (QP)

Detector that weights a signal by its repetition rate; the higher the rate the higher the reading. The reference detector for CISPR limits.

Peak Detector첨두 검출기

Detector that captures the maximum of the input. Fastest, and always at least as large as QP or average, so it is used for pre-scans.

Average Detector (AV)평균 검출기 (AV)

Detector measuring the average signal level; useful for separating narrowband signals from broadband noise.

EMI ReceiverEMI 수신기

A dedicated receiver meeting CISPR 16-1-1 with preselection and standardised detectors.

Spectrum Analyzer스펙트럼 분석기

Instrument displaying signal level versus frequency. Widely used for pre-compliance; formal tests need EMI-receiver functionality.

Pre-scan프리스캔

A fast peak scan that finds candidate frequencies before precise QP/AV measurement.

Noise Floor잡음 바닥

Lowest measurable level, set by the receiver’s own noise.

Ambient Noise주변 잡음

External signals (broadcast, communications) present regardless of the EUT, degrading radiated-test reliability.

Preamplifier프리앰프

Low-noise amplifier raising small signals above the receiver noise; its gain must be subtracted in the conversion.

Attenuator감쇠기

Passive device reducing a signal by a fixed number of dB; protects receivers from overload and improves matching.

Directional Coupler방향성 결합기

Device that samples forward and reflected waves separately; used to monitor forward and reflected power in immunity tests.

Current Probe전류 프로브

Clamp-on probe measuring conductor current without contact, converted using its transfer impedance.

Near-Field Probe근거리장 프로브

Small probe for locating E- or H-field sources on a board; used for tracking down emission sources.

1 dB Compression Point (P1dB)1 dB 압축점 (P1dB)

Output level at which amplifier gain drops 1 dB below its linear value; the practical operating limit.

Calibration교정

Procedure comparing an instrument, antenna or cable with a standard to establish correction values and uncertainty.

Test Sites & Antennas

Semi-Anechoic Chamber (SAC)반무반사실 (SAC)

Test room with a metal reflecting floor and absorber-lined walls and ceiling; the standard environment for 3 m/10 m radiated-emission tests.

Fully Anechoic Room (FAR)전자파 무반사실 (FAR)

Test room with absorbers on all surfaces including the floor; used for emission tests above 1 GHz and for radiated immunity.

Open-Area Test Site (OATS)개방형 시험장 (OATS)

Outdoor test site over open ground; the reference site, but affected by weather and ambient noise.

Shielded Room차폐실

Metal-walled room blocking external fields; used for conducted tests and to keep ambient noise out.

Ground Plane접지면

Reference conductive plate of the test setup; the standard prescribes size, material and spacing to the EUT.

Turntable턴테이블

Rotating platform turning the EUT through 360° to find the direction of maximum emission.

Antenna Mast안테나 마스트

Mast moving the antenna between 1 and 4 m to find the maximum of floor-reflection interference.

Biconical Antenna바이코니컬 안테나

Broadband antenna for about 30–300 MHz, built from two cone-shaped elements.

Log-Periodic Antenna로그주기 안테나

Directional broadband antenna covering roughly 200 MHz to 1 GHz and above.

Bilog Antenna바이로그 안테나

Hybrid of biconical and log-periodic designs covering 30 MHz–1 GHz with one antenna.

Horn Antenna혼 안테나

Directional antenna for measurements above 1 GHz and immunity tests, with stable gain.

Normalized Site Attenuation (NSA)정규화 사이트 감쇠 (NSA)

Metric for validating a test site by comparing measured site attenuation with the ideal value within a tolerance (typically ±4 dB).

Field Uniformity Area (UFA)전계 균일 영역

Plane area where the field stays within a tolerance during radiated immunity tests; calibrated before testing.

TEM Cell / GTEM CellTEM 셀 / GTEM 셀

Waveguide-like test fixture producing a TEM wave inside for testing small devices.

Reverberation Chamber반향실

Metal chamber using multiple reflections and a stirrer to create a statistically uniform field.

Design & Mitigation

Shielding Effectiveness (SE)차폐효과 (SE)

Ratio (dB) of field level without and with the shield; the sum of absorption and reflection loss.

Insertion Loss삽입손실

Reduction in signal (dB) when a filter or component is inserted in the circuit.

Return Loss반사손실

Ratio (dB) of incident to reflected power; larger means a better match.

VSWR정재파비 (VSWR)

Ratio of maximum to minimum standing-wave voltage on a line; closer to 1 means a better match.

Reflection Coefficient반사계수

Amplitude ratio Γ of reflected to incident wave. VSWR and return loss are both expressed through Γ.

Characteristic Impedance특성 임피던스

Ratio of voltage to current on an infinitely long line; common values are 50 Ω and 75 Ω for coax.

Ferrite Bead페라이트 비드

Component with resistive impedance at high frequency that dissipates noise as heat; used on power and signal lines.

Common-Mode Choke공통모드 초크

Two conductors wound on one core so that only common-mode current sees a high impedance.

X CapacitorX 커패시터

Safety-rated capacitor across the mains lines (L–N) reducing differential-mode noise.

Y CapacitorY 커패시터

Safety-rated capacitor between line and earth (L–PE) that shunts common-mode noise; capacitance is limited by leakage-current limits.

Decoupling Capacitor디커플링 커패시터

Capacitor placed near an IC power pin that supplies high-frequency current locally and reduces supply noise.

Self-Resonant Frequency (SRF)자기공진주파수 (SRF)

Frequency at which a component resonates due to its parasitics; above it a capacitor behaves like an inductor.

Snubber스너버

RC (or RCD) circuit that damps ringing and spikes from switching devices.

Spread-Spectrum Clocking (SSC)확산 스펙트럼 클럭 (SSC)

Slightly modulating the clock frequency to spread energy over a wider band; lowers peaks but total energy stays the same.

EMI GasketEMI 개스킷

Conductive part that seals enclosure seams against leakage.

Aperture (Slot) Leakage개구(슬롯) 누설

Electromagnetic energy leaking through gaps and holes in a shield; nearly unshielded when the longest dimension approaches λ/2.

Pigtail피그테일

Connecting a cable shield to ground through a short wire; its inductance greatly degrades high-frequency shielding.

360° Shield Termination360° 차폐 종단

Connecting the cable shield around its full circumference to the connector shell; far better than a pigtail.

Bonding본딩

Connecting metal parts with low impedance; contact surface finish and area decide high-frequency performance.

Mains Filter (EMI Filter)전원 필터 (EMI 필터)

Filter of X/Y capacitors and a common-mode choke that reduces conducted emissions and incoming noise on the mains.

TVS DiodeTVS 다이오드

Device that clamps transient voltages to protect circuits; a basic ESD and surge protection part.

Balun발룬

Device converting between balanced and unbalanced lines; can suppress common-mode current caused by imbalance.

Immunity Testing

Electrostatic Discharge (ESD)정전기 방전 (ESD)

Short, intense discharge between charged objects. IEC 61000-4-2 defines contact and air-discharge tests.

Electrical Fast Transient (EFT/Burst)전기적 빠른 과도현상 (EFT/Burst)

Bursts of fast pulses from switching inductive loads; tested per IEC 61000-4-4.

Surge서지

High-energy transient voltage/current from lightning or heavy switching; tested per IEC 61000-4-5.

Radiated Susceptibility/Immunity Test방사 내성 시험 (RS)

Applying an external field to the EUT to check for malfunction; examples are IEC 61000-4-3 and MIL-STD-461 RS103.

Conducted Susceptibility/Immunity Test전도 내성 시험 (CS)

Injecting a disturbance onto cables or power lines to check for malfunction; for example IEC 61000-4-6 and MIL-STD-461 CS114.

Bulk Current Injection (BCI)벌크 케이블 주입 (BCI)

Test method injecting induced current into a cable bundle with an injection probe; widely used in automotive and military standards.

Amplitude Modulation (AM)진폭 변조 (AM)

Varying a carrier’s amplitude with a signal; 1 kHz, 80 % AM is the standard in immunity testing.

Performance Criteria (A/B/C)성능 판정 기준 (A/B/C)

Categories describing the degradation allowed during or after an immunity test; A is the strictest.

Voltage Dip전압 강하

Temporary drop in supply voltage; tested per IEC 61000-4-11.

Flicker플리커

Visible flicker of lighting caused by supply-voltage fluctuation; measured with a flickermeter and covered by both emission and immunity standards.

High-Altitude EMP (HEMP)고고도 전자기 펄스 (HEMP)

Broadband electromagnetic pulse from a high-altitude nuclear burst; tests are covered by IEC 61000-4-25 and others.

Equipment Under Test (EUT)시험 대상 장비 (EUT)

The product being tested; operated in its worst-case mode during the test.

Auxiliary Equipment (AE)보조 장비 (AE)

Additional equipment (loads, laptops, sensors) connected to operate the EUT; controlled so that it does not influence the result.

Uncertainty, Certification & Regulation

Margin마진

Difference (dB) between limit and measured value; design targets commonly require at least 3–6 dB.

Measurement Uncertainty측정 불확도

Quantified range within which a result may deviate from the true value, built from cable, antenna, receiver and mismatch contributions.

Coverage Factor (k)포함인자 (k)

Factor multiplying the combined standard uncertainty to give expanded uncertainty; k = 2 is about 95 % confidence.

Expanded Uncertainty확장불확도

Combined standard uncertainty multiplied by the coverage factor: U = k·u_c.

Root-Sum-Square (RSS)제곱합 제곱근 (RSS)

Method of combining independent error terms: u_c = √(Σu²).

Guard Band가드밴드

Internal pass line set inside the limit to account for uncertainty, defined by certification body or manufacturer policy.

Uncertainty Distribution불확도 분포

Probability distribution of an uncertainty component (rectangular, triangular, U-shaped, normal); each has its own divisor.

Site Validation시험장 검증

Procedure (for example NSA) confirming that a test site meets the standard’s requirements.

Pre-Compliance프리컴플라이언스

Preliminary evaluation done before formal testing, with in-house or external facilities, reducing retest cost and schedule risk.

Test Plan시험 계획서

Document fixing in advance the EUT configuration, operating modes, applicable tests, limits and pass criteria.

Class A / Class B등급 A / B

Equipment classification by environment; B is for residential use with stricter limits.

Basic Standard기본 규격

Standard that defines test methods only (for example IEC 61000-4-x); levels and judgement come from the product standard.

Product (Family) Standard제품(군) 규격

Standard setting limits, test levels and criteria for a product family (for example CISPR 32, CISPR 35).

CE MarkingCE 마킹

Conformity mark for the European market; compliance with the EMC Directive (2014/30/EU) is required.

KC CertificationKC 인증

Safety and EMC conformity mark required for equipment placed on the Korean market.

FCC Part 15

The part of U.S. FCC rules setting emission requirements for intentional and unintentional radiators, with Class A/B.

CISPR

The IEC’s International Special Committee on Radio Interference; publishes emission limits and measurement standards (CISPR 11, 16, 32, …).

MIL-STD-461

U.S. DoD standard controlling the electromagnetic-interference characteristics of military equipment.

Edition / Amendment에디션·개정

Standards are revised periodically and limits or methods can change, so the applicable edition must be stated for testing.