Wideband End-Wall Transition From Microstrip to Waveguide With via-Less Choke Structure for Terahertz Application

In the end-wall transition from planar lines to waveguide, the via holes are generally arranged around the waveguide port to prevent power leakage, which increases production cost and manufacturing errors in terahertz band. In this letter, a novel wideband transition from microstrip to waveguide with via-less choke structure is proposed. A simple rectangular patch is utilized to convert the quasi-TEM mode of microstrip line to the TE
₁₀
mode of waveguide. In place of the via holes, multiple open stubs are introduced to suppress the power leakage. Furthermore, an extra resonant mode is generated by controlling the length of open stubs, which leads to a wider working band. Two back-to-back prototypes with different lengths are designed and fabricated over 300 GHz. The simulated and measured results are in good agreement. The measured return loss of single transition is better than 12 dB with an insertion loss of 0.9 ± 0.11 dB in the range of 314–369 GHz (16.1% bandwidth).