Phase Stability Tests with a Millimeter Wave Network Analyzer

Short-term phase uncertainties in certain commercial millimeter wave vector network analyzers seem to be partly related to errors in their internal reference oscillators despite the selected operating principle. Sudden phase jumps up to 0.5 degrees and lasting for 5 - 20 seconds have been observed and correlated results of 0.05 degrees at 100 GHz are demonstrated together with a phase drift lasting several hours from start-up. The poor frequency stability of internal references and the lack of any locking capability further reduce the possibility for long-term comparisons against known external sources.