However, if they are not suitable or available, clamp injection should be used.
Often, clamp injection needs to be applied to multi-pair balanced cables because suitable CDNs might not be available.
The EM clamp establishes both capacitive and inductive coupling to the cable connected to the EUT.
The EM clamp (in contrast to the conventional current injection clamp) has a directivity ≥ 10 dB, above 10 MHz, so that a defined impedance between the common-mode point of the AE and the ground reference plane is no longer required.
Above 10 MHz, the behaviour of the EM clamp is similar to that of a CDN.