Design of a non-contact high-power broadband coaxial rotary joint

Background Rotary joints serve as critical feeder-link components in high-power mechanical beam-scanning antenna systems, ensuring efficient and stable radio-frequency energy transmission during antenna rotation. As high-power microwave technology steadily advances toward wideband operation, miniaturization, high efficiency, and high reliability, microwave rotary joints are required to meet correspondingly stringent demands.

Purpose Compared with circular-waveguide rotary joints, coaxial rotary joints feature a more compact structure and offer better system adaptability in low-frequency bands. However, conventional coaxial rotary joints typically suffer from narrow bandwidth, insufficient power-handling capacity, and wear-prone contact-type structures. To satisfy the evolving requirements of high-power microwave systems, a broadband coaxial rotary joint with high power-handling capacity is needed.

Methods This paper proposes a contactless high-power broadband coaxial rotary joint design that combines a stepped-waveguide multi-section impedance transformer with a novel choke structure, thereby achieving broadband and highly efficient rectangular TE₁₀-coaxial TEM-rectangular TE₁₀ mode conversion.

Results The proposed structure was modeled and optimized using full-wave electromagnetic simulation software. Simulation results show that over the 1.68-2.58 GHz frequency range, the device achieves a transmission efficiency greater than 99%, a return loss better than 20 dB, and a power-handling capacity on the gigawatt order, corresponding to a fractional bandwidth of up to 42% at a center frequency of 2 GHz.

Conclusions The design collectively realizes high power-handling capacity, wide bandwidth, high efficiency, and contactless rotation, offering a high-performance rotary joint solution with promising engineering application prospects for high-power mechanical beam-scanning antenna systems.