Noise reduction for three plate circulator - uses chamfered microwave ferrite discs in inner conductor region

摘要

The circulator, as used in microwave communications systems as a transmit-receive switch, of three plate junction type comprises outer conductors (4) of non-magnetic material which carry the permanent magnet inserts (3) and soft iron pole shoes (5) which connect with the microwave ferrite discs (7). The inner conductor (6) is sandwiched between the discs. Where the inner conductor crosses the edges of the discs these are chamfered. Typically the chamfer covers between a third and three-quarters of the disc thickness, and has an angle between 10 and 40 degrees to the disc plane. The arrangement results in an improvement in signal to noise ratio of from 9dB to 7dB. In circulators without pole shoes the chamfering faces the outer conductors.