VLF-VHF EMC Filter Design Criteria

Many EMC filter applications require equipment and shielded enclosure power line filtering of 100 db or greater over frequency ranges of 1. 0 kc to 1. 0 or 10 . 0 kmc. Completely different design techniques are necessary in three different frequency ranges, such as 1. 0 kc to 15-25 kc, 15-25 kc to 75-100 kc through 1. 0-10 . 0 kmc. In the low frequency range of 1. 0 kc to 15-25 kc, true low pass filters working into known impedances are necessary to pass the power line frequencies, without high power losses which would destroy the filter. In power line and information circuits, particularly those carrying digital signals, the filters must be in critical damped circuits to prevent ringing.