Low-Power Testing of Losses in Millimeter-Wave Transmission Lines for High-Power Applications

摘要

We report the measurement of small losses in transmission line (TL) componentsintended for high-power millimeter-wave applications. Measurements were made using twodifferent low-power techniques: a coherent technique using a vector network analyzer(VNA) and an incoherent technique using a radiometer. The measured loss in a 140 GHz12.7 mm diameter TL system, consisting of 1.7 m of circular corrugated waveguide andthree miter bends, is dominated by the miter bend loss. The measured loss was 0.3±0.1 dBper miter bend using a VNA; and 0.22±0.1 dB per miter bend using a radiometer. Goodagreement between the two measurement techniques implies that both are useful formeasuring small losses. To verify the methodology, the VNA technique was employed tomeasure the extremely small transmission loss in a 170 GHz ITER prototype TL systemconsisting of three lengths of 1 m, 63.5 mm diameter, circular corrugated waveguide andtwo miter bends. The measured loss of 0.05±0.02 dB per miter bend may be compared withthe theoretical loss of 0.027 dB per miter bend. These results suggest that low-power testingof TL losses, utilizing a small, simple TL system and a VNA, is a reliable method forevaluating performance of low-loss millimeter-wave TL components intended for use inhigh-power applications.