S.N. Boiko, M.V. Kovaleva, A.S. Petrov
The engineering technique of designing triple-band aircraft transmitter antenna for KOSPAS-SARSAT (KS) system was developed. The electrical scheme with three monopole-type antennas, matched with 50 Ohm feeder by inductive L-sections and band-pass channel filters from lumped-elements combined at an output point, forming triplexer, was proposed. It was established that successive inductor mounted in L–section gives the main part of dissipative losses and thus its value must be minimized. Designed antenna has VSWR<2, maximum gain (1.6, 2.0 и 2.5) dBi and bandwidth (1.8, 3.1 и 18)% at three KS frequencies (121.5, 243 и 406) MHz respectively. Antenna has dimensions (240x190x60) mm, and weighs 0.5 kg. The original and reliable embedded lightning protection system was proposed. Elements dimensions of lightning-conductor topology were established experimentally at the special lightning imitation stand equipment with impulse currents, like in real lightning.