Design and Implementation of a TEM Cell with Piecewise Linear Tapering

The transverse electromagnetic (TEM) cells are used for electromagnetic interference/compatibility (EMI/EMC) experiments of the small RF devices in a laboratory environment. The standard electromagnetic fields generated in the shielded environment of a TEM cell can also be used for calibration of the RF field probes. In this paper, a 50 W open TEM cell is designed and fabricated to generate standard electromagnetic fields from 1 MHz up to 1 GHz. To overcome the impedance mismatch and improve the voltage standing wave ratio (VSWR) along the TEM cell, a new piecewise linear tapering method is proposed for the inner conductor of the cell. The resulted matching conditions of the new tapering method are presented through some numerical simulations and measurements and compared to those of the conventional simple linear tapering.