TEMZ 5232, DC - 200(1000) MHz, Open, unsymmetrical 50 Ohm stripline

Open, unsymmetrical 90 Ω stripline for automotive immunity testing of components. (A wooden frame construction is required to bear the stripline, not included in delivery)

Termination resistor 90 W mounted on an aluminum plate to fit the open, unsymmetrical stripline TEMZ 5232. The power rating of the resistor is 60 W, which is sufficient for generating field strengths up to 500 V/m. A high impedance RF-voltmeter with an appropriate divider can be used to measure the cell-voltage at the BNC-connector. The field strength inside the cell can be obtained by multiplying the voltage reading with factor 6.67 (adding 16.5 dB). In direct surrounding to the termination resistor, an increase of field strength appears, therefore a minimum spacing of 30 cm between EuT and termination should be provided.

Application:

The unsymmetrical 90 W stripline complies with the requirements of ISO 11452-5. The stripline can be used to create TEM-waves up to max.220 MHz. The field strength distribution at TEM-mode operation inside the stripline is very homogenous. The stripline can also be used above 220 MHz, in this case, higher modes do exist, which offer a location dependant field strength characteristics. In contrast to the TEM-mode, where the field strength is small at the edge of the stripline and increases towards the center, the higher modes show opposite characteristics: the field strength is small at the center of the stripline and rises to maximum values at the edge of the strip conductor. Further, the direction of polarisation changes in some areas during multi-mode operation. At TEM-mode operation there are only small losses caused by radiation and dielectric losses of the plastic support rods. Approx. 8% of the incident power is reflected back into the source due to the characteristic line impedance of 90 W, which corresponds to a nominal average VSWR of 1.8. An ideal tool for monitoring the actual field strength inside the stripline is the VUFM 1670 field meter with VUFM 1671 LCD display unit, which is connected via a fiber optical link. For positioning of the EuT it is recommended to use (nearly) dielectric neutral material, e.g. foam or polystyrene plastics. The suitability of the material can be checked as follows: the return loss of the empty cell is measured, then the material under test is placed in the cell and the insertion loss is measured again. Minimum differences in attenuation of the empty and loaded cell indicate a suitable material. The equipment under test (EuT) should be placed in the center of the stripline. It is recommended to record the EuT-position and the cable location as exactly as possible in order to achieve good reproducibility of the tests.

Example of Frame Construction:

The unsymmetrical 90 W stripline can be used in vertical as well as horizontal orientation. For room-economic reasons a wall mount in a shielded room or anechoic chamber is often preferred. Simple construction of square timbers or laths is shown in the drawing. When selecting the square timber, be sure that the total distance from the wall is min. 120 mm. After the desired position of the N-connector is known, the 4 long parts can be mounted first, followed by the 10 cross-bars and finally the two end bars. The large aluminum plates of the stripline can be drilled according to the lath-construction and fixed with wood-screws.