Causes and cures.

Intermodulation problems due to non-linearities have been a problem for a long time. With increasing demand for mobile communications, the need for greater channel capacity and more sensitive receivers have made Passive Intermodulation Distortion (PMD) more of a problem than ever.

There are many causes of PMD in a communications system. One that directly affects PolyPhaser and its products are connectors and connections to them. The following list was compiled from several articles on PMD.

• Restrict connector materials to copper and copper alloys.

• Connector body plating of silver or white bronze with a minimum plating thickness of 6u m (0.0002 in.).

• Avoid use of stainless, nickel, or ferrite in signal path.

• Quality machining - minimum finish of .4 mm.

• Properly designed interface at connect, panel, and contact surfaces.

• Avoid crimp connections - all connections should be soldered. Clamp and solder outer contacts for best static and dynamic performance.

• DIN connectors are less susceptible to Intermodulation than N connectors.

• Avoid hermetic seals containing Kovar.

Connectors used by PolyPhaser including 7/16 DIN are supplied with gold center contact pins.