A mm-Wave D-Band Vector Network Analyzer of High Dynamics

In highly oversized waveguide components used for high power mm-wave transmission, it is necessary to determine the spectrum of modes propagating while in operation. Therefore, low power measurements are useful to get an overview. Also, possible tuning can be done safely at low power levels. The wavenumber spectrometer turned out to be an excellent measuring tool for determining the mode mixture in oversized waveguides [1][2]. To prevent interference with the electromagnetic fields inside the spectrometer, the coupling factor is held very low, less than -60 dB. Additionally, the efficiency of low power quasi-optical mode generaters for high order gyrotron-type modes (e.g. TE22,6), is under 30%. To achieve reliable measurements under such conditions, a network analyzer with a dynamic range over 100 dB should be used [3]. Commercially available network analyzers above 110 GHz lack either in band-width, handling (tunable resonators), dynamic range or are very expensive.