Correction of manufacturing deviations in waveguide filters and manifold multiplexers using metal insertions

Microwave filters and multiplexers commonly employ tuning screws to compensate for small errors occurring during the fabrication process. Nevertheless, the use of tuning screws has some disadvantages, because the small gaps between the screws and the holes are prone to create unwanted effects when dealing with high-power signals, especially for space applications, and are also the source of potential radiation losses. In this paper, an alternative technique to correct manufacturing deviations is presented, in which tuning screws are replaced by fixed metal insertions. In this case, the correction is made by means of designing new insertion pieces that will be able to correct those small deviations. In order to find the dimensions of the new pieces, a space-mapping technique is applied. For verification purposes, the method has been applied over a circular-waveguide dual-mode filter and later over a manifold multiplexer containing the same type of filters. However, the technique can be directly extended to other types of waveguide filters and multiplexers where tuning screws are also employed.