An Efficient SPICE-compatible Circuit Model for Transmission Line Response Excited by an Electrically Short Dipole Inside a Metallic Cavity

For the transmission line response excited by an electrically short dipole inside a rectangular cavity, a SPICE-compatible broadband Foster type equivalent circuit is presented. The electric field inside a cavity is represented by the eigenmode decomposition of Helmholtz equation, while the current of transmission line is expanded using the eigenmode of transmission line equation. The field-to-line coupling effect is described by the Agrawal formula. The convergence of the circuit is accelerated by the extraction of quasi-static inductances and capacitances. The validity and efficiency of the presented method is verified both in frequency and time domain. Also, the effects of lossy filling material are discussed. Besides, in order to show the aggravation effect of metallic cavity on the electromagnetic interference, the induced currents on the transmission line with and without a metallic casing are given and compared.