How do CISPR 22 Class A and Class B limits compare to FCC Part 15?

FCC Part 15 Subpart B defines Class A (commercial) and Class B (residential/domestic) limits that are very similar to CISPR 22 but not identical. Key differences: FCC conducted emission limits are measured over 450 kHz to 30 MHz (versus CISPR's 150 kHz to 30 MHz start frequency). FCC radiated limits use 3 m and 10 m measurement distances depending on class, while CISPR 22 uses 10 m and 30 m. The numerical limits in dBuV/m are adjusted for distance but result in comparable stringency. FCC also requires testing to 40 GHz for devices with clock frequencies above 1.705 GHz, while CISPR 22 originally stopped at 1 GHz (later extended to 6 GHz).

What equipment falls under CISPR 22 versus CISPR 11?

CISPR 22 (now CISPR 32) covers information technology and multimedia equipment: computers, servers, networking gear, printers, monitors, smartphones, tablets, and telecom infrastructure. CISPR 11 covers industrial, scientific, and medical equipment: power supplies, motor drives, RF heaters, plasma systems, medical devices, and laboratory instruments. The distinction is functional: if the equipment processes information or multimedia content, it falls under CISPR 32. If it generates, transforms, or distributes electrical energy or uses RF energy for material processing, it falls under CISPR 11. Some equipment may need to comply with both standards if it serves dual functions.

EMC Standards & Regulations

CISPR 22

Q: Why was CISPR 22 superseded by CISPR 32?

As technology evolved, the distinction between ITE (CISPR 22) and broadcast receivers/multimedia equipment (CISPR 13) became artificial. A modern smartphone is simultaneously ITE, a multimedia player, and a broadcast receiver. CISPR 32 merges CISPR 22 (ITE emissions) and CISPR 13 (broadcast receiver emissions) into a single standard covering all multimedia equipment. The emission limits in CISPR 32 are largely identical to CISPR 22 for ITE functions, but add requirements for equipment with audio/video functions. The transition period ended in 2019, and EN 55032 replaced EN 55022 as the EU harmonized standard.

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An international EMC standard that defined conducted and radiated emission limits for information technology equipment (ITE) from 150 kHz to 1 GHz (later extended to 6 GHz). CISPR 22 established the Class A (commercial) and Class B (residential) framework adopted globally. Harmonized in the EU as EN 55022 and closely mirrored by FCC Part 15 Subpart B. Officially superseded by CISPR 32 in 2015, which merges ITE and multimedia equipment into a single emission standard, but CISPR 22 limits remain the de facto reference for ITE compliance testing.

Category: EMC Standards

Status: Superseded by CISPR 32

EU: EN 55022 → EN 55032

Understanding CISPR 22

CISPR 22 was first published in 1985 as the primary emission standard for the rapidly growing computer and telecommunications industry. It defined measurement methods and limits for both conducted emissions (measured at the AC mains port via a LISN) and radiated emissions (measured in a semi-anechoic chamber or open-area test site). The standard distinguished between Class A equipment (intended for commercial, industrial, or business environments) and Class B equipment (intended for residential use or connection to the domestic power network), with Class B limits being approximately 10 dB more stringent.

For RF engineers designing computing and networking equipment, CISPR 22 compliance was often the most challenging regulatory hurdle because digital clock frequencies (100 MHz to 5 GHz) generate harmonics throughout the critical radiated emission bands. Common mitigation techniques include multi-layer PCB stackups with dedicated ground planes, ferrite chokes on I/O cables, shielded enclosures with conductive gaskets at seams, and spread-spectrum clocking (SSC) to distribute harmonic energy across a wider bandwidth. The standard's measurement methodology using quasi-peak and average detectors, 120 kHz resolution bandwidth for conducted and 120 kHz/1 MHz for radiated, and specific LISN impedance requirements became the foundation for EMC testing worldwide. While CISPR 32 formally replaced CISPR 22, the technical limits are essentially unchanged for pure ITE products.

CISPR 22 Key Emission Limits

Conducted Emissions (0.15 to 30 MHz):
Class B QP: 66 to 56 dBμV ; Class B AV: 56 to 46 dBμV
Class A QP: 79 to 73 dBμV ; Class A AV: 66 to 60 dBμV

Radiated Emissions (30 to 230 MHz):
Class B: 30 dBμV/m at 10 m ; Class A: 30 dBμV/m at 30 m

Radiated Emissions (230 to 1000 MHz):
Class B: 37 dBμV/m at 10 m ; Class A: 37 dBμV/m at 30 m

QP = quasi-peak detector (CISPR 16-1-1), AV = average detector. Measurement bandwidth: 9 kHz (Band A), 120 kHz (Band B), 120 kHz to 1 MHz (above 1 GHz).

CISPR 22 vs FCC Part 15 Comparison

Parameter	CISPR 22 / EN 55022	FCC Part 15 Subpart B
Conducted Start	150 kHz	150 kHz (450 kHz for some)
Radiated Max (original)	1 GHz (extended to 6 GHz)	Up to 40 GHz (if clock > 1.705 GHz)
Class B Distance	10 m	3 m
Class A Distance	30 m	10 m
Detector	QP + AV	QP (AV for some bands)
Successor	CISPR 32 / EN 55032	Still Part 15

Common Questions

Frequently Asked Questions

Why was CISPR 22 superseded by CISPR 32?

Modern devices blur the ITE/multimedia boundary (a smartphone is simultaneously ITE, media player, and broadcast receiver). CISPR 32 merges CISPR 22 (ITE) and CISPR 13 (broadcast receivers) into a single standard. Technical limits for ITE are largely identical. EN 55032 replaced EN 55022 in the EU; the transition ended in 2019.

How do CISPR 22 limits compare to FCC Part 15?

Similar but not identical. FCC uses different measurement distances (3 m/10 m vs CISPR's 10 m/30 m), starts conducted at 450 kHz for some equipment, and extends radiated to 40 GHz for high-clock-rate devices. Numerical limits are adjusted for distance but provide comparable stringency. Products sold globally typically test to both.

What equipment falls under CISPR 22 vs CISPR 11?

CISPR 22/32: information technology and multimedia (computers, networking, smartphones, telecom). CISPR 11: industrial, scientific, medical (power supplies, motor drives, RF heaters, plasma, medical devices). Dual-function equipment may need both. The distinction is functional: information processing = CISPR 32; energy processing = CISPR 11.

Related Terms

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