Targeted Resonance Control in a TEM Cell

We investigate extending the upper frequency limit of an asymmetric ldquoCrawford-style'' transverse electromagnetic (TEM) cell with targeted resonance control. Focusing on the fundamental TE cavity resonance, an active feedback cancellation system is applied with the aim of reducing the resonant field amplitude without affecting the desired TEM mode. A half loop J-dot current probe is positioned with a vertical polarization on one wall of the TEM cell to measure the wall currents generated from the TE resonance. An identical probe is placed on the facing wall that is connected to the first through a negative feedback chain. The second loop's purpose is to excite a field that has the appropriate magnitude and phase to attenuate the TE resonance amplitude. Experimental application achieved a 17-dB reduction in the amplitude of the resonance field. The method is also outlined with respect to the TE resonance. This system is planned for full-scale implementation into a hybrid reverberation/TEM whole-aircraft electromagnetic vulnerability testing facility.