Rigorous modal S-matrix analysis of the cross-iris in rectangular waveguides

A rigorous field theory analysis is presented for cross-irises in rectangular waveguides, as well as for cross-iris coupled rectangular waveguide resonators. Arbitrary iris location, unequal E-and H-plane cross size and finite thickness are rigorously taken into account. The scattering parameters of a cross-iris coupled one-resonator filter in the waveguide Ku-band (12-18 GHz) are presented as a calculation example. The theory is verified by comparison with available data for cut-off frequencies, as well as with measurements.<>