Although this is not shown, if the frequency is increased to approximately 7.9 GHz, the short appears as an open, and the open appears as a short! In fact, on a 26.5 GHz 3.5 mm kit, the arcs would have gone around the Smith Chart more than once! Many people do not expect this, so are confused, and believe there's a problem. As you can see, they are arcs, even on this very expensive Keysight 85052B 26.5 GHz 3.5 mm calibration kit. The cyan trace shows the result of measuring the open circuit which is stored in memory. The sweep range has been limited to 7 GHz, with markers at the lowest frequency (50 MHz), as well as 500 MHz, 2 GHz, 4 GHz and 7 GHz. S-parameters and think they have a problem as after measuring the opens and shorts are shown as arcs, not dots as they expected! The photograph below shows the HP 8720D VNA screen after the calibration standards of an expensive HP 85052B (26.5 GHz 3.5 mm) were measured. In any text book on transmission lines which show a Smith Chart, an open circuit is shown on the right (phase angle = 0°) and short circuit on the left (phase angle = 180°), as shown on the following Smith ChartĪfter performing a calibration of a VNA, many people put the open and short calibration standards on the VNA, measure their Why measuring the calibration standards on a VNA results in arcs, not dots on a Smith Chart as most people expect. Why VNA calibration standards are arcs on a Smith Chart, not dots
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