What is the CISPR 25 artificial network and how does it differ from a LISN?

The CISPR 25 artificial network (AN) provides a defined impedance on the DC power supply lines to the DUT, isolating the measurement from external noise while presenting a repeatable source impedance. Unlike the CISPR 16 LISN used for AC mains measurements (50 ohm parallel with 50 microhenry), the CISPR 25 AN uses 5 ohm in series with 1 microhenry, better representing the low-impedance vehicle battery bus. The AN includes a 50-ohm measurement port for connecting the EMI receiver. Multiple AN types are defined: AN for power supply lines, AN for signal lines, and AN for high-voltage lines (EV/HEV applications with 400V to 800V DC bus).

How are CISPR 25 radiated emission measurements performed?

The DUT is placed on a ground plane (metallic table) inside a shielded enclosure lined with absorber material. The measurement antenna is positioned 1 m from the DUT edge in the horizontal plane. Four antenna types cover the full frequency range: a 1-meter rod antenna (monopole) for 150 kHz to 30 MHz, a biconical antenna for 30 to 200 MHz, a log-periodic dipole array for 200 to 1000 MHz, and a horn antenna for 1 to 2.5 GHz. The DUT wiring harness is routed along the ground plane for a specified length (1.5 m typical), and measurements are taken with the antenna both parallel and perpendicular to the harness to capture both common-mode and differential-mode radiation.

EMC Standards & Automotive

CISPR 25 Detail

Q: What frequency bands does CISPR 25 protect?

CISPR 25 divides the spectrum into frequency bands corresponding to actual vehicle receiver services: Band LW (150 to 300 kHz, longwave broadcast), Band MW (530 to 1710 kHz, AM broadcast), Band SW (5.9 to 6.2 MHz, shortwave), Band FM (76 to 108 MHz, FM broadcast), Band TV (174 to 230 MHz, DAB/TV Band III), Band CB (26 to 28 MHz, citizen's band), Band DAB-L (1452 to 1492 MHz, L-band DAB), Band GPS (1575 MHz, GPS L1), Band cellular (824 to 960 MHz and 1710 to 2170 MHz), and higher bands for WiFi and V2X. Each band has specific limits reflecting the receiver sensitivity in that service.

Detailed Test Methods & Limits

A detailed reference for CISPR 25 automotive EMC test methods, covering the complete test setup: artificial network (AN) specifications (5 Ω + 1 μH per power line), shielded enclosure requirements, antenna types and placements (rod for 150 kHz to 30 MHz, biconical for 30 to 200 MHz, log-periodic for 200 MHz to 1 GHz, horn for 1 to 2.5 GHz), frequency band definitions aligned with AM, FM, DAB, GPS, cellular, and WiFi receiver services, and the complete severity class limit tables for all five classes across conducted and radiated measurements.

Category: EMC Test Methods

Test Distance: 1 m

AN Impedance: 5 Ω + 1 μH

CISPR 25 Test Setup Details

The CISPR 25 test environment consists of a shielded room (minimum 3 × 3 × 3 m clear volume) with RF absorber material on walls, ceiling, and floor (except the ground plane area). The DUT is mounted on a metallic ground plane representing the vehicle body, with a wiring harness of defined length (1.5 m typical) routed along the ground plane at 50 mm height on non-conductive supports. The DC power supply is connected through an artificial network (AN) that provides a repeatable measurement impedance and isolates external noise.

The AN for CISPR 25 differs fundamentally from the CISPR 16 LISN used for AC mains equipment. While the LISN presents 50 Ω parallel with 50 μH (suitable for 50/60 Hz AC mains), the automotive AN presents 5 Ω in series with 1 μH, representing the low-impedance vehicle battery bus. This lower impedance is critical because vehicle wiring harnesses are short (1 to 5 m) with low inductance, and the battery presents a near-short circuit at RF frequencies. Conducted emissions are measured at the AN's 50 Ω output port using an EMI receiver with quasi-peak (QP) and average (AV) detectors. For high-voltage EV applications (400V to 800V DC bus), dedicated HV-ANs with appropriate voltage isolation are used. The complete measurement covers conducted emissions on all power and signal lines, plus radiated emissions with four antenna types covering 150 kHz to 2.5 GHz.

CISPR 25 Measurement Parameters

AN Impedance:
Z_AN = 5 Ω + jω · 1 μH [per supply line]

Radiated Measurement Distance:
d = 1 m from DUT edge to antenna reference point

Harness Length:
L_harness = 1.5 m (routed at 50 mm above ground plane)

Antenna factors convert measured voltage to field strength: E (dBμV/m) = V (dBμV) + AF (dB/m). Resolution bandwidth: 9 kHz (Band A, 150 kHz to 30 MHz), 120 kHz (Band B, 30 MHz to 1 GHz), 1 MHz (above 1 GHz).

CISPR 25 Antenna Selection by Band

Frequency Range	Antenna Type	Polarization	Services Protected
150 kHz to 30 MHz	1-m rod (monopole)	Vertical	LW, MW, SW, CB
30 to 200 MHz	Biconical	H + V	FM, VHF TV
200 MHz to 1 GHz	Log-periodic dipole	H + V	DAB III, cellular 800/900
1 to 2.5 GHz	Horn	H + V	DAB-L, GPS, cellular 1.8/2.1
2.5 to 6 GHz (ext)	Horn	H + V	WiFi, V2X, UWB

Common Questions

Frequently Asked Questions

What is the CISPR 25 artificial network?

The AN provides 5 Ω + 1 μH per power line, representing the vehicle battery bus impedance (vs LISN's 50 Ω + 50 μH for AC mains). It includes a 50 Ω measurement port for the EMI receiver and isolates external noise. HV variants handle 400V to 800V for EV/HEV testing.

How are radiated emissions measured?

The DUT sits on a ground plane in a shielded room with absorber. Four antenna types at 1 m distance cover 150 kHz to 2.5 GHz. The harness is routed 1.5 m along the ground plane at 50 mm height. Measurements are taken with the antenna parallel and perpendicular to the harness to capture all radiation modes.

What frequency bands does CISPR 25 protect?

Bands align with vehicle receivers: LW (150 to 300 kHz), MW (530 to 1710 kHz), FM (76 to 108 MHz), DAB III (174 to 240 MHz), cellular (824 to 960 MHz and 1710 to 2170 MHz), DAB-L (1452 to 1492 MHz), GPS L1 (1575 MHz), WiFi (2.4 GHz), and V2X (5.9 GHz). Each band has service-specific limits.

Related Terms

← CISPR 25 CISPR 32 →