Efficient Approaches to Eliminate Influence Caused by Micro-machining in Fabricating H-plane Iris Band-pass Filters

Due to the limitations of micro-machining processes, in a manufactured H-plane iris band-pass filter, the corners between the waveguide walls and irises are round angles rather than right angles. Based on the mode matching method, this paper investigates the influence caused by the H-plane round angles. Three efficient approaches are presented to eliminate this undesired influence: compensating the frequency shift, offsetting the shift with bevel angles and taking the properties of the perturbations into account when computing the sizes. The methods are applied to a Chebyshev iris band-pass filter with a center frequency of 94GHz and a fractional bandwidth of 4.25%. All approaches successfully correct the offset of the center frequency caused by the 0.4mm radius rounded corners and all calculated results are verified by full-wave simulations using ANSYS HFSS.