Downsizing of LPDA for radiation EMI measurement

In this paper, a log-periodic dipole antenna array (LPDA) was downsized by using chip inductors and dielectric substrate for outdoor measurement. It was found that the directivity of a dipole antenna was decreased with increase of the shortening ratio of the element. A three-element LPDA was designed using the downsized dipole element. The reflection characteristics of the fabricated LPDA met the target value between 282 MHz – 385 MHz. The fabricated LPDA had about half length compared with that of original one, and the flat gain of from −0.46 to 1.89 dBi were obtained.