A mode extraction network for rf sensing in satellite reflector antenna

An alternative to rf sensing techniques that involves a multimode monopulse configuration in which specific higher order asymmetric waveguide modes provide the required error signals in a Cartesian coordinate system is discussed. Based on a single-feed aperture, this configuration offers a high tracking sensitivity without unduly compromising the communication channel performance. Its operation is based on the principle that if the antenna points away from the designated beacon source the asymmetry thus created results in the excitation of a number of higher order modes in the waveguide of the antenna feed system. If selected modes are sensed, then signals derived from these modes can be used to control the satellite positioning mechanism to reorient the antenna. In addition to its high sensitivity, an antenna of this type has no moving parts and requires only a single primary feed horn.