MIL-STD-220A versus Classical Measurement of Filter Insertion Loss in a 50-ΩSystem

Discrepancies have been observed in the data obtained from measurement of insertion loss using MIL-STD-220A and other classical and more traditional techniques. This situation has resulted in confusion for designers of interference-suppression components, raising doubts regarding the validity of MIL-STD-220A and correctness of the test procedures specified therein. In this paper, a complete analysis of the test circuit described by MIL-STD-220A is performed. Using the circuit characteristics of the matched isolation attenuators, an equation is derived for the filter insertion loss. It is shown that, for large values of attenuation provided by matched isolation attenuators, the values of insertion loss obtained become nearly equal to the values obtained from the classical equation of the insertion loss, which agree with experimental results.