Accurate and efficient design approach of substrate integrated waveguide filter using numerical TRL calibration technique

In this paper, a numerical TRL calibration technique is used to accurately extract the equivalent circuit parameters of post-wall iris and input/output coupling structure which are used for the design of directly-coupled substrate integrated waveguide (SIW) filter with the first/last SIW cavities directly excited by 50 Ω microstrip line. On the basis of this dimensional design process, the entire procedure of filter design can meet all of the design specifications without resort to any time-consuming tuning and optimization. A K-band 5^th-degree SIW filter with relative bandwidth of 6% was designed and fabricated by low-cost PCB process on Rogers RT/duroid 5880. Measured results which agree well with simulated results validate the accurate dimensional synthesis procedure.