The design and analysis of an inline (0°) E-Plane microstrip line-to-WR5 transition using an antipodal dipole antenna at a frequency of 180 GHz for mm-wave and lower THz applications are presented in this article. The impedance matching between the MS-line and antipodal dipole antenna and mode matching between the MS-line and rectangular waveguide (RWG) are achieved using an impedance transformer. The excellent performance of transitions is obtained because of the parasitic loading of the transition with a 14-capacitive array. There is insertion loss (IL> \(\:-\) 0.15 dB) and return loss (RL< \(\:-\) 19 dB) with the proposed change over a 44.44% relative bandwidth (39.5% fractional bandwidth) from 166.19 GHz to 203.46 GHz. The lowest values of IL and RL were − 0.17 dB and − 17.23 dB obtained at a frequency of 140 GHz, respectively. A double-sided high-permittivity of 12.4 and 50 μm thick InP-Substrate for Microstrip-Launcher reduces radiation loss while reducing the maximum fractional bandwidth (FBW). The design transition is simple, easy to manufacture, robust, compacted, and cost-effective since no ridge waveguide or waveguide back shorts are deployed in WR5. Also, it does not require any additional numbers of vias, fences, windows, screws, galvanic structures, posts, etc. Hence, the design transition is a suitable candidate for radio astronomy, amateur satellites, earth exploration satellites, radiolocation, and radio navigation satellites, suitable for direct integration with MMIC circuits and mm-wave, sub-mm-wave, and lower THz frequency mixers, amplifiers, and other applications. This transition is also applicable to the radiometric imaging system and G-band radiometer systems used to generate mm-wave images.
