Dual mode coupling by square corner cut in resonators and filters

A novel method for realization of dual mode coupling in rectangular waveguide cavities is described and analyzed. This method completely replaces the coupling screw, and therefore can be used to eliminate the need for tuning in dual mode waveguide cavity filters. It also offers a wide range of coupling values and can achieve higher power handling capability than coupling screws. The mode matching method is used to calculate the mode chart of the infinite corner cut rectangular waveguide, the field distributions of each mode, and the resonant frequencies of the cavity. The dual mode coupling parameter is calculated from resonant frequencies and is verified by measurements. A C-band four-pole dual mode elliptic function rectangular waveguide cavity filter using the new coupling method was constructed and tested. The experimental results showed excellent agreement with theory.<>