The transfer function between the intentional electromagnetic interference (IEMI) attacker and the engine control unit (ECU) circuit in an automobile is extracted to analyze how the IEMI affects the vehicle. A log-periodic antenna is used as the IEMI aggressor based on the frequency domain measurement and the transfer function of the log-periodic antenna is compared with the transfer function of the standard mesoband source generator measured in the time domain. The electric field of the standard source is regenerated with the transfer function of the log-periodic antenna. It is then compared with the original field of the standard source to validate the transfer function of the log-periodic antenna. Since the D-dot sensor is used to measure radiated field in the time domain, a noise in low frequency region is amplified and it is investigated.