An Open Standing-Wave TEM (STEM) Cell for Field-Enhanced Radiation Immunity Measurement

In this letter, we propose a new immunity measurement device based on a modified transverse electromagnetic (TEM) cell. Initially, a wideband open TEM cell with a working range from DC to 8.1 GHz is designed with excellent impedance matching. Building upon this design, a movable short-circuit piston is integrated. Unlike the conventional TEM cell, which generates a traveling wave, this modified structure produces a standing wave along the longitudinal direction, so this modified TEM cell is defined as standing-wave TEM (STEM) cell. By moving the short-circuit piston, from the perspective of time-averaged statistic, the maximum field strength inside this modified structure doubles, which is helpful for reducing the power requirement of the immunity testing. Moreover, the theoretical foundation of the STEM cell is established through transmission line-based equivalent circuit modeling and cutoff frequency analysis. Finally, it is used to test the radiation immunity of a DC-to-DC converter module to validate the doubled field strength.