Design of an Integrated Switching Antenna for Shielding Effectiveness Testing of Small Enclosures From 1 MHz to 100 MHz

Modern aircraft is exposed to a variety of risks from electromagnetic environment (EME), and electromagnetic shielding is a useful method for protecting electronic equipment from the severe EME. In the meanwhile, aircraft employs more integrated modular avionics, whose enclosures are much smaller than conventional ones. Therefore, it is critical to invent new equipment for measuring the shielding effectiveness (SE) of small enclosures. This article proposes an integrated switching antenna composed of a square wave generator, switching circuit, impedance matching circuit, compact monopole, and battery. The SE of a tiny enclosure at several frequencies can be tested with an integrated switching antenna in a single test. Furthermore, the proposed construction does not require an external signal generator, which eliminates the need for any enclosure cuts for attaching a coaxial cable or soldering an antenna. To test the feasibility of the proposed antenna, a prototype is built to measure the SE of a tiny enclosure. The measurement shows a good agreement between the measured and simulated results. Furthermore, using the inverse fast Fourier transform, the time-domain SE may be determined from the frequency-domain measurements in the frequency range of 1 to 100 MHz. The calculated time-domain SE results could be useful for determining the amount of protection against lightning and high-altitude electromagnetic pulse.