Broadband Coaxial Rotary Joint With Simple Substrate Integrated Waveguide Feeder

This paper presents a broadband coaxial rotary joint with simple single-layer substrate integrated waveguide (SIW) feeder. The annular slot etched on the surface of SIW can effectively convert TE10 mode in the rectangle SIW into the rotational symmetric TEM mode in the coaxial line. Broadband impedance matching can be achieved because the additional capacitive coupling between the short-circuited circular metallic patch and coaxial line. Comparing with previous SIW fed rotary joints, the proposed design has the advantages of wider bandwidth and simpler feeding structure. The equivalent circuit is given to explain the design. A prototype centered at 12 GHz is fabricated with the 10-dB impedance matching bandwidth of 24.9% and the minimum insertion loss of 0.3 dB.