The Spaceborne Imaging Radar-C, X-Band Synthetic Aperture radar (SIR-C/X-SAR) Mission Overview

The rotor of the joint includes two rectangular waveguide ports, carrying two separate signals. The stator has two corresponding rectangular waveguide ports. The ports are coupled with a circular waveguide, which comprises two relatively rotatable stub-cylinders, disposed co-axially in-line on the axis of rotation. Signal A is transmitted through the circular waveguide, across the joint, in the TM01 propagation mode, while signal B is transmitted across the joint in the TE01 mode. These circular-symmetrical modes, with mutually orthogonal field distribution, are able to cut cross-talk interference, since the mode transducers of these modes maintain good mutual isolation, even though the signals are present together in the circular waveguide, and at the same or similar frequency. The TM01 mode (signal A) is excited, and received, by means of slots formed in the end wall of the circular waveguide stubs. The port for signal A communicates with the circular waveguide through the two slots. The TE01 mode (signal B) is excited, and received, by means of four axial slots formed in the cylindrical wall of the circular waveguide. The transducer for signal B is disposed in a wrap-around relationship with the circular waveguide, and is in communication with the circular waveguide through the four slots. An E-plane junctional continuation communicates the port for signal B, via two slots, with the transducer for signal B.