A large "flat biconical" antenna for LLSC aircraft-illumination in the HF band

In previous papers, an analysis of the coupling of external high frequency (HF) electromagnetic waves to aircraft wiring was presented, and a methodology for measurement of aircraft shielding effectiveness in the HF band using the low level swept coupling (LLSC) method was presented. The effectiveness of this test method is primarily determined by the field generation capability of the test set-up. In this paper, a "flat biconical" illuminator, constructed for these tests, is described. The illuminator is basically constructed of two sections, each formed in the shape of a triangle, somewhat resembling the profile of a biconical antenna. The dimensions of the illuminator, scaled to the HF band, were selected such that it is closely "tuned" to 10 MHz. This configuration was expected to provide sufficient bandwidth to the illuminator, ensuring little incident E-field variation over the entire test frequency range. The radiation characteristics of the illuminator as well as a comparison between its measured and computed characteristics are presented. From the data provided, it may be concluded that the proposed illuminator is a cost-effective, easy to construct and efficient illuminator for the HF band, for the purpose of LLSC assessment.