Two current probes are designed with the appropriate magnetic material in order to make impedance measurements in High Frequency (HF) using the Current Injection Method (CIM). These probes are then used to measure the commonmode impedance of power converters in real-operating conditions. The characterization of this impedance is required for a correct EMI filter design. In this paper, a simple formulation of the probe transfer impedance, based on S-parameters, is proposed. These probes allow improving the accuracy of impedance measurements in a wide frequency range, up to 100 MHz. The measured impedances of the power converter are then applied in the design of the common mode EMI filter under real operation conditions. The obtained insertion losses of the filter are finally compared with those measured under 50 Ω- 50 Ω.