engleski

Design of a TEM-cell with Increased Usable Test Area

Abstract: Transversal Electromagnetic Mode Cell (TEM-Cell) is used for electromagnetic compatibility measurements (emission and immunity), and for biomedical applications. Over the years, higher and higher frequencies are being used. This demands smaller transmission structures in order to obtain the homogenous field distribution due to the resonance. The resonance destroys the TEM field, introducing the higher order modes. The goal was to design the TEM-cell for GSM frequencies that will have a larger area with homogenous field used for testing, while still obtaining the characteristic impedance. Commercial TEM-cell used for frequencies of 900 MHz have only 2 cm in height available for testing, while the proposed TEM-cell has 5 cm in vertical dimension suitable for EMC testing. The problems regarding the characteristic impedance, resonance, higher order modes, dimensions and usable test area are discussed. Numerical modeling with the "Quickfield" which uses Finite Element Method (FEM) and "MAFIA" which uses Finite Integration Technique (FIT) gave the electromagnetic field distribution and calculation of the higher order modes. The measurements of VSWR and insertion loss showed good correlation with the model. At 935 MHz, the VSWR is 1, 1 which makes the cell applicable for GSM frequencies. The higher order modes appear at 490 MHz and 740 MHz, but other frequency area is usable. The TEM-cell has characteristic impedance of 75 and increased usable test area. It can be utilized for EMC measurements and biomedical applications from DC to 1 GHz.

TEM-cell; design

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