A Dissipative Coaxial RFI Filter

A lossy coaxial filter has been developed to protect electroexplosive devices from accidental detonation by stray high-power RF fields. The characteristics of a coaxial transmission line, filled with dielectromagnetic material, are analyzed in terms of various proposed filter configurations. The design concept for the prototype filter is chosen so as to provide a maximum stop-band attenuation. Measured results are presented to show that the filter provides an insertion loss of about 90 db from 5 Mc to at least 10 kMc. Furthermore, it is shown that the use of a lossy filter guarantees a minimum value of insertion loss regardless of the terminating impedances.