Microwave transmission means with improved coatings

摘要

Band pass filter incorporated in a duplex base station cellular telephony transmit/receive system have aluminum parts having plated thereon a composite coating which is entirely of nonferromagnetic materials (to reduce creation in the filter of intermodulation products) and which consists of a zinc layer on an aluminum substrate and copper and silver layers outward in that order from the zinc layer and having respective thickness of at least about 300 microinches, and of at least about 500 microinches (to reduce resistance losses incurred by microwaves traveling throughout the filter). The filters also include other parts which are interiorly of brass and some of which are silver plated, all to the end of further reducing such intermodulation products and losses. The filters have input and output ports provided by coaxial fittings press fitted into bores in a wall of the filter to thereby reduce intermodulation products caused by contact non-linearities.