12-GHz Rotary Joint With Substrate Integrated Waveguide Feeder

In this paper, a rotary joint fed by the substrate integrated waveguide (SIW) feeder is presented. This structure is able to effectively convert the TE
₁₀
mode in the SIW with arbitrary input angle to the symmetrical TM
₀₁
mode in the circular waveguide. A good matching can be implemented by use of a tapered dual-side parallel strip line (DSPSL) between a SIW and a printed probe. After introducing the design principle, a rotary joint prototype with two controllable transmission poles is fabricated and measured. From 11.6 to 12.6 GHz, its insertion loss is always less than 1.09 dB and return loss is better than 11.22 dB when being rotated at different angles. Besides, a tapered slot antenna (TSA) is employed to realize a rotary antenna based on the rotary joint proposed above. Stable performance and different polarizations can be achieved at different rotary angles. Based on the rotary joint with the SIW feeder, it is much more convenient for designers to extend the application field of the SIW devices.