Mutual Coupling in Compact Orthomode Transducers

TL;DR

This paper analyzes mutual coupling in compact orthomode transducers with azimuthally-distributed probes, deriving conditions under which mutual coupling cancels, enabling low-noise radiometric receiver designs.

Contribution

It provides theoretical expressions for mutual coupling in dual-mode waveguide orthomode transducers with multiple probes, demonstrating conditions for zero or coherent cancellation.

Findings

Mutual coupling can be zero or cancel coherently in these transducer topologies.

The analysis applies to both three- and four-probe configurations.

Results suggest potential for low-noise radiometric receiver implementations.

Abstract

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.