A non-contacting, broadband rotary joint, and four-way switch

Recent advances in the field of passive electronic intelligence systems have required the development of high gain very broadband electro-mechanically scannable antenna systems. Consequently the need has arisen for various types of signal transfer devices. This paper describes the development of a novel rotary joint and rotary switch. Both units employ unique electrical and mechanical design techniques which provide excellent electrical performance characteristics and the capability of operation at angular velocities in excess of 3000 RPM. The rotary joint is of necessity a completely non-contacting device due to the requirement that it shall operate satisfactorily at extremely high rotational speeds. Therefore, in order to provide the desired bandwidth, in excess of 12.5 to 1, a novel capacitive coupling technique was developed which virtually eliminates the frequency sensitivity of the conventional quarter-wave choke type configuration. The second requirement for high speed switching between antenna arrays and elements has dictated a need for a four-way rotary switch. The unit is basically a cylindrical strip transmission line configuration, and operates on the quarter-wave choke principle. Theoretical and experimental investigations indicate that satisfactory operation can be achieved over a 2:l bandwidth within the VHF to S-band region.