Conducted RF immunity testing - Observed variation in the injected current

IEC 61000-4-6 relates to the conducted immunity requirement to electrical and electronics equipment to electromagnetic disturbances coming from intended RF sources in the frequency range of 150 kHz to 80 MHz. The standard defines different injection methods for applying RF stress level over the test frequency range. The purpose of the test is significant when the impedance of the disturbance source during setting the stress level and during the test is same. Variation in common mode impedance causes variation in injected stress level. This paper points out the inefficiency in the injection methods for stabilizing the impedance and practical results are shown.