Measurement of disturbances at telecommunication ports by using both voltage and current probes

Method of measuring disturbances at telecommunication ports has been publis hed by IEC/CISPR. A method using both disturbance voltage and current probe s is useful because it does not require any impedance stabilization network s (ISNs). In this paper, the values measured using this method are theoreti cally and experimentally compared with those measured using ISNs. An experi ment using a simple circuit model presents that the value obtained by using this method is lower than that by using ISNs in some cases. A theoretical analysis however derives that the estimated value by adding the margin to t he measured value is always guaranteed to be large compared with the value measured by ISNs. The analysis also indicates that the margin is dependent on the deviation of phase angle of ISN and can be calculated by a simple eq uation. The experiment using actual equipment shows that the estimated resu lts including the margin is always larger than those measured by ISNs. The results of the study show that the method using both disturbance voltage an d current probes can be used for measuring the disturbances by taking the m argin into account, and this margin can be reduced by improving the phase a ngle characteristics of the common mode impedance of ISNs.