Bandwidth-Reconfigurable Coaxial Bandpass Filter With Multi-Octave Tuning Using a Single Element

A widely bandwidth tunable coaxial-loaded waveguide filter is presented in this paper based on a novel concept using a single common tuning element. The operation principle relies on the rotation of coaxial resonators with respect to fixed iris windows to control the inter-resonator coupling strengths and tune the bandwidth. This mechanism features multi-octave tuning capabilities, while maintaining a fixed operation frequency and a stable high unloaded quality factor through only one rotary post, without the need for any additional tuning element. Additionally, the filter can be switched-off effectively through the same arrangement without the necessity for any switching components. A prototype is manufactured, assembled, and measured to verify the design process of the proposed filter. The first experimental results demonstrate a wide bandwidth tunability from 12 MHz to 83 MHz (tuning ratio > 1:6.9), promoting the technique for many multi-standard communication systems and applications.