Development of Functional Broadband Microstrip-to-Folded SIW Ku-Band Transition

This letter presents a novel design methodology of a potent low-loss wideband microstrip-to-T-type folded substrate integrated waveguide (MS-TFSIW) transition that achieves significant impedance-matching performance. The proposed design embodies multiobjective multivariable optimization on several rows of central and lateral vias and the tapering part at the feed edge. These include optimum diameter, pitch, and location from the edge, in conjunction with optimum positioning of end vias on both side walls from the edges of TFSIW. Moreover, a field matching technique for the gradual distribution of electric field over the microstrip and TFSIW region is applied by incorporating a tapered transition at the central septum part. The proposed technique shows significant wideband improved impedance matching and achieves a simulated return loss of less than 30 dB and maximum insertion loss of 0.29 dB across bandwidth for the Ku-band. The Ku-band MS-TFSIW transition is fabricated and measured. The measured return loss is below 24.52 dB for the entire band of operation with 0.7 dB transmission loss. A comparative study on the state-of-the-art design of other reported transitions between planar lines and multilayer SIWs is compared and listed.