On 8/18/23 8:15 AM, Brian Beezley wrote:
On Tue, Aug 15, 2023 at 09:25 PM, Jim Lux wrote:
Sometimes, I find the derivative of unwrapped phase (group delay) more useful,
too.
Jim, your comment inspired me to add group delay to my program. I don't see its relevance for ground probe data, but it provides a powerful diagnostic tool that can reveal anomalies otherwise invisible. The first two plots show an ordinary-looking phase plot and the corresponding group delay plot. The big group delay spike corresponds to a barely perceptible flat spot in the phase curve. It's easier to see in the third plot with a narrower frequency span. I think it's due to a VNA frequency stepping issue.
Yeah, derivatives do accentuate noise - but sometimes that's actually useful to spot a discontinuity in a system that should otherwise be "smooth" And when you have multiple resonances, is makes them obvious.
