W-Band Broadband Transition from Microstrip to Waveguide and Analysis of the Effect of SIW Substrate

In this paper, a broadband microstrip to waveguide transition with a vertical structure working on W-band is proposed. The substrate integrated waveguide (SIW) is used as the transition between the waveguide and the microstrip. The transition from SIW to rectangular waveguide (RWG) is completed by inserting a dielectric substrate. Through utilizing a steplike bend waveguide with ridges, excellent impedance matching and vertical transmission are accomplished. The working principle of the transition structure is studied by field analysis, and the influence of different shapes of substrate inserted into the RWG on S-parameters is discussed. The simulation results show that the working bandwidth of the transition can cover the W -band, in which the reflection coefficient is less than -15 dB, and the insertion loss is better than <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{- 0. 2 6 ~ d B}$</tex>.