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Common Mode Absorbing Device – CMAD

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SIQ Developed CMAD

Our commitment to quality has brought us to the development of a Common Mode Absorbing Device – CMAD, which will ensure a higher level of confidence in EMC testing according to CISPR 16-2-3. We hereby present our first CMAD prototype, developed by the SIQ R&D team, which complies with CISPR 16-1-4.

For reproducible radiated emission measurements, it is not always sufficient to have a measurement location, antenna, and EMI receiver calibrated, although their effects are considered during testing. It is also important to have a defined common-mode impedance for the cables leaving the measurement setup. The CMAD ensures adequate cable terminations, which reduces the influence of AC or DC mains supply or auxiliary equipment on the measurement results. The CMAD is placed on cables leaving the test volume in radiated emission measurements, which reduces variations in measurement results between different test locations (semi-anechoic chamber, GTEM cell, etc.).

The fruitful collaboration between the SIQ EMC and Metrology departments resulted in a new compliant device and calibration service, which will ensure a higher level of confidence in SIQ product testing and certification.

The purchase and calibration of the CMAD are also available to our valued customers.

Contact us for more information:  safety@siq.si

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SIQ Ljubljana

Safety and Electromagnetics
Mašera-Spasićeva ulica 10
1000 Ljubljana

EMC calibration

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The ferrite clamp CMAD fulfills the following specifications:

  1. The magnitude of S21 shall be less than 0,25 in the frequency range from 30 MHz to
    200 MHz,
  2. The magnitude of S11 shall be within the following limit ranges in the frequency range from 30 MHz to 200 MHz.
    a. Upper limit 0,75 at 30 MHz and 0,55 at 200 MHz (decreasing linearly with the logarithm of the frequency)
    b. Lower limit 0,6 at 30 MHz and 0,4 at 200 MHz (decreasing linearly with the logarithm of the frequency)

CMAD calibration

The CMAD is constructed of clamp ferrites, which are used in radiated emission measurements below 1 GHz to reduce compliance uncertainty. Electromagnetic characteristics of the CMAD are calibrated according to CISPR 16-1-4.

The CMAD shall be placed on cables leaving the test volume in radiated emission measurements in compliance with the latest CISPR 11, CISPR 14-1, CISPR 16-2-3, IEC 61000-6-3,
IEC 61000-6-4, and the latest medical standard IEC 60601-1-2:2014 + A1:2020 (Edition 4.1).

S11

S11 represents CMAD input reflection coefficient at EUT side measured by Vector Network Analyzer. Standard CISPR 16-1-4 defines frequency-dependent upper and lower limits of S11 in the frequency range from 30 MHz to 200 MHz.

S21

S21 represents the CMAD transition coefficient from EUT to the AUX side. Standard CISPR 16-1-4 defines the upper limit, which is not frequency depended and goes from 30 MHz to 200 MHz.