Approximate design equation for Iris width calculation of Iris Substrate Integrated Waveguide (SIW) bandpass filters

This paper presents the approximate design equation for iris width calculation of Iris Substrate Integrated Waveguide (SIW) bandpass filter. The design equation has been derived by using curve fitting techniques followed by de-embedding method and it is valid for narrowband band pass filter design; the fractional bandwidth (FBW) should not be more than 10%. A generalized procedure has been presented to calculate the inverter parameters of the iris window. At 60 GHz frequency, the design equation has been developed for its validation. The theoretical and calculated normalized reactance values are in good agreement. An iris SIW bandpass filter at 60 GHz has also been designed using the developed procedure.