Measured insertion loss (top), the measured and simulated reflection coefficients (middle), and the cross-polarisation and isolation (bottom) of the NAOJ OMT. The reflections are shown for the Waspnet simulations, which are in good agreement with the HFSS simulations. The insertion loss measurement is limited to frequencies <112 GHz by the waveguide extenders used in the measurement setup. The loss is expected to remain flat or decrease at higher frequency.