Critical Upsets of CMOS Inverters in Static Operation Due to High-Power Microwave Interference

The effects of electromagnetic interference (EMI) from high-power microwave signals on the operational integrity of CMOS inverters are reported. The static characteristics of inverters were measured with and without the injection of microwave signals at power levels of upto 24 dBm and frequencies between 800 MHz and 3 GHz. Voltage transfer characteristics showed significant changes in output voltages, and substantial reduction in gain with microwave interference, due to increased drain currents and reduced transconductance, respectively. The asymmetry of the MOS devices (size, mobility) designed to provide balanced current driving capability, results in significantly imbalanced current driving capabilities under interference. A substantial increase in the static power dissipation at the stand-by "ON" and/or "OFF" states, is observed. Degradation in the noise margins and severely compressed input/output voltage ranges were observed due to large changes in voltage characteristics, invalidating noise immunity of cascaded CMOS inverters, and leading to serious bit-flip errors. The load-line characteristics showed substantial shift in the quiescent point of operation, and changes in the effective "ON" resistance of the MOS devices, resulting in increased current in the inverters. The input/output voltage range-related bit-flip errors and the static power dissipation problems, represent the most critical vulnerabilities in the operational integrity of digital systems.