We report on advanced techniques for the characterization of millimeter-wave orthomode transducers (OMTs). These techniques include standard mm-wave frequency-domain VNA (Vector Network Analyser) measurement and time-domain methods, which can be applied to remove the effects of the waveguide transitions necessary to access the OMT ports and excite the desired modes. First, we present the main parameters of the OMT by defining its general S-matrix and discuss the different methods that allow characterizing the insertion loss, the reflection, the cross-polarization and the isolation of the device. Advantages and disadvantages of each method are presented and compared between them. We provide a list of waveguide components necessary in the various OMT test setups (adapters, loads, quarter-wave and longer waveguide sections, feed-horn, etc.). Different OMT configurations, with distinct orientation of the waveguide input and outputs are discussed. Alternative characterization methods of the OMT parameters are presented and the associated setups discussed.
Although the presented techniques refer to the characterization of a specific configuration of a W-band (3 mm wavelength) OMT, the described method can be applied to other OMT configurations and frequency ranges (from microwave to THz frequencies), therefore having a general validity
