V-band rotary joint with low loss over wide bandwidth

We describe a rotary joint that offers < 0.5 dB insertion loss within a 13% bandwidth about 60 GHz. The joint is comprised of two mode converters arranged back-to-back that transform the dominant TE10 mode in standard WR-15 rectangular waveguide to TE01 mode in circular cylindrical waveguide at which rotation occurs. We present data that show that wideband performance depends on stringent quality control in manufacturing the part.