Figure 4

2D sketch of slot element with the radial stub. (a) Front view. (b) Bottom view. Some optimized key parameters (length in mm) are: \(w_s=0.2\), \(d_1=4\), \(r_s=4.7\). (c) Exploded view of the SIW structure with the decoupling stub, the insert indicates that the metallic via is insulated from the ground. (d) Scattering parameters with Port-1 at end of the coaxial line and Port-3 connected to the end of DC bias line with and without radial decoupling stub. (e) Scattering parameters between Port-1 and Port-2 of the SIW structure with (red solid line) and without (black solid line) radial decoupling stub.