MIL-STD-220 Method Of Insertion Loss MeasurementThis standard covers a method of measuring, in a 50 ohm system, the insertion loss of feed-through suppression capacitors, and of single and multiple circuit radio frequency RF filters at frequencies up to 10 gigahertz GHz.

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MIL-STD-220C

APPENDIX A

Figure A-2 shows an example of a filter connector that has a filter ground problem.  This situation could be the result of poor impedance in the array ground or the connection to the connector shell.  The trace noted as Thru Pin shows poor attenuation at higher frequencies.  The measurement of the insertion loss between this pin and an adjacent pin shows an insertion loss that almost matches the thru pin insertion loss at higher frequencies.  There is RF signal on the ground plane and it is being coupled into the adjacent contact.  The bottom trace shows the insertion loss to the fixture and is indication of a good fixture ground.  This signal should have attenuation levels 10 dB to 20 dB or greater than the desired measurement level (Thru Pin).  This says that the shell plating is good and that the connection to the bulkhead is also good.

FIGURE A-2.  Insertion loss poor filter ground to shell.

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