Microwave waveguide filter with broadside wall slots

An investigation into rectangular waveguide filters with open slots on the broad side walls is reported. This type of waveguide filter eliminates the need for direct contact between the two waveguide halves and intentionally leaves a gap in the middle of broad side walls. For X-band (8.2-12.4 GHz) waveguides, such a gap can be nearly as wide as 9% of the internal waveguide width a, without introducing any significant radiation loss. A fifth-order filter centred at 10 GHz with a fractional bandwidth of 2% is designed based on such a structure, and fabricated from aluminium and tested. There is good agreement between measurement and simulation results. This verifies the proposed structure as well as the design procedure.