  The scattering parameters of generalized compact orthomode transducers using
azimuthally-distributed field probes in a dual-mode waveguide are analyzed.
Theoretical expressions constraining the mutual coupling between the probes are
derived and evaluated for three- and four-probe orthomode transducers with and
without a coaxial reference port for calibration injection. The mutual coupling
is shown to be identically zero or cancel coherently in all cases, suggesting
that radiometric receivers with the best possible system noise temperature may
be realized using these topologies.
