A DIRECTION FINDING OF CONDUCTED INTERFERENCE USING THE COUPLED TRANSMISSION-LINES

As a method of evaluating the direction of arrival of conducted interf erence propagating along a transmission line, a measurement method usi ng coupled transmission lines is investigated. The principle of measur ement is the direction selectivity of the coupled transmission lines c onsisting of two parallel lines. The direction of propagation of the c onductive noise is sensed from the difference of the response voltages at the two ends of the coupled transmission line. In the present expe riment, a strip line with a characteristic impedance of 50 ohms made o f a two-sided substrate of length 12 cm and width 3 cm is used as the coupled line. With this test transmission line, the coupling character istics of the transmission lines are experimentally confirmed based on a homogeneous transmission line model. With a standard power supply c ord as the line under test, the response voltage for the conducted ele ctromagnetic interference generated from a small generator is measured . It is confirmed that the response voltage of the coupled line depend s on the direction of propagation of the transient voltage propagating along the transmission line. Hence, it is shown that detection of the direction of propagation of the conducted interference can be carried out easily. (C) 1997 Scripta Technica, Inc.