Methods of Improving High Frequency Direct Injection Testing

摘要

Direct injection testing is a valuable tool for identifying electromagneticeffects and critical subsystems prior to expensive, labor intensive free-field testing. However, as the frequencies of interest increase, the method becomes less reliable and the measurement techniques become more difficult. A major problem has been the frequency response of the voltage probes. This effort has identified the cause of the degradation of the voltage dividing ratio with frequency, through experiment and circuit simulation, as a capacitive effect. Moreover, the effective capacitance has been quantified, and constraints on the resistive element have been devised. An improved compact voltage probe is demonstrated which shows a flat frequency response to 3 GHz. Other issues which have been addressed are the importance of measuring the node impedance to ground; comparison of direct injection vulnerability levels with those obtained with free field testing; the practice of using incident power as a metric; using a transmission line as a voltage probe; and probe loading effects.