A Compact Waveguide Filter Based on Loaded Metal Posts

This paper proposes a method for designing compact waveguide filter by loading metal cylindrical posts and metal rectangular posts. Metal rectangular posts are placed on different coupling paths to introduce resonant modes. In addition, positive coupling and negative coupling can be obtained depending on the number of loaded rectangular posts. The metal cylindrical posts can be regarded as the ridge used to compress conventional rectangular cavity resonators. A compact fifth order waveguide filter is designed based on loading metal posts. The theoretical analysis and design process of filter are given in detail. The measured results are in good agreement with the theoretical simulated results, where the return loss is greater than 15dB.