A wideband fully enclosed coaxial-to-substrate-integrated waveguide transition and its applications in a 1-to-4 radial power divider

Abstract

Aimed at the interconnection between coaxial transmission line and substrate-integrated waveguide (SIW), a wideband coaxial-to-SIW transition was proposed and applied in a 1-to-4 radial power divider. First of all, a fan-shaped region was designed on the end of a SIW transmission line. Then, a coaxial transmission line was inserted into this region. To improve the impedance matching at the coaxial port, a feeding ring was designed on the back of the transition where the coaxial line was inserted. Next, the transition was applied in a 1-to-4 radial power divider to realize an equal power division. Finally, to validate the correctness of the designs, prototypes were fabricated and measured. For the coaxial-to-SIW transition, measured reflection coefficient |S₁₁| was less than −15 dB from 7.84 to 12.18 GHz. Transmission coefficient |S₂₁| was between −0.52 and −0.24 dB. For the 1-to-4 radial divider, measured |S₁₁| was less than −15 dB from 7.91 to 12.4 GHz, and the transmission coefficient was around −6.9 dB. Measurement and simulation agreed well with each other. Therefore, the proposed design can be used in coaxial-to-SIW interconnection scenarios.