Electric Field Sensor Approach to Determine Fidelity and Overmoding Region of GTEM Cell

Characterizing new electric field (E-field) sensors requires knowing the frequency limits of one’s radio-frequency (RF) chamber. A commonly used RF chamber is called a gigahertz transverse-electromagnetic (GTEM) cell that supports transverse-electromagnetic (TEM) fields through the gigahertz spectra. This manuscript proposes a new methodology for determining the range of usable frequencies within a GTEM cell having unknown characteristics (e.g., after moving a GTEM cell from one laboratory to another). Above a certain frequency, all frequencies become overmoded and yield unreliable measurements. We found that comparing international standards to measured data can provide insights into where overmoding occurs. The comparison to international standards was assisted by a derived free-space wave impedance formula in the frequency domain using both flush-plate dipole (D-dot) and magnetic field (B-dot) probes. Overall, this article proposes a new tool for determining the operating frequencies at which GTEM cells can reliably function in accordance with international standards before overmoding occurs.