Transverse electromagnetic mode cells (TEMCells) are used for electromagnetic compatibility measurements and biomedical applications. Since The source excitations and the field distributions are usually in the shape of transient pulses, A time-domain method is used for analyzing the electromagnetic field distributions inside a TEM cell. This paper employs The method of moments to solve the governing Electric Field Integral Equation. The metallic structure of the cell is modeled as a grid of conducting wires and then the method is applied to the structure. Having obtained the field distribution inside the cell, one can specify the uniform region inside the cell, wave impedance and the voltage standing wave ratio of the cell, which determines the usable bandwidth of the cell
