article „how to avoid Gibbs ringing artifacts in measurements“ in Signal Integrity Journal

[senmeis]

Hi,

I’m reading the article „how to avoid Gibbs ringing artifacts in measurements“ in Signal Integrity Journal at https://www.signalintegrityjournal....avoid-gibbs-ringing-artifacts-in-measurements and have a few questions on this topic.

1. Figure 5 and 8: Do they refer to the s-parameters of the interconnect?

2. From other books I acquired the oscilloscope bandwidth shall be at least 3 times of the signal bandwidth. Is this requirement just the one this article insists (1/BW)?

3. What about older analog oscilloscopes? They don’t have a sharp brick wall filter characteristics. Do they also bring Gibbs artifact?

4. In control theory these ripples are considered as the result of a low damping ratio. Does this explanation coincide with this filter theory?

 

[senmeis]

No one cares about this topic? I’m only able to view if from the control aspect (because of my limited background), lead lag controller, PID controller, etc.

 

[FvM]

Most oscilloscopes have smooth vertical amplifier frequency characteristic that doesn't involve significant ringing, both old analog and modern digital types. For me the article is discussing a mostly theoretical problem. If we see ringing in oscilloscope measurements it's mostly caused by bad probe connection. Sufficient bandwidth is nevertheless required for reproduction of pulse waveforms.

 

[danadakk]

Interesting discussion over here - https://www.eevblog.com/forum/testgear/split-from-rigols-new-dho800-oscilloscope-unbox-amp-teardown/

 

[BradtheRad]

Hi,

oscilloscope bandwidth shall be at least 3 times of the signal bandwidth. Is this requirement just the one this article insists (1/BW)?

I have a 1960-era Tektronix tube scope rated 1 MHz. (And the timebase selector limits to 1µHz.) I've been surprised to see onscreen waveform frequencies 2 or 3 times that. However I don't trust the amplitude readings because I don't expect those waveforms to be traced accurately.

3. What about older analog oscilloscopes? They don’t have a sharp brick wall filter characteristics.

My Tektronix manual instructs how to calibrate sharpness of leading edges by adjusting a potentiometer. As I do so the appearance gets rounder or spike-y. That section has capacitors and an inductor. The manual doesn't mention Gibbs' ringing.

 

[senmeis]

Thanks for above info. Let’s focus on Figure 5. This is a test result, not of an oscilloscope but of a TDR device. As far as I understand this measurement tries to express: The signal has a bandwidth of 39 GHz but the S-parameters of the used connector are limited to 40 GHz. That is the reason of this ringing effect (as FvM mentioned due to this poor connector). Do I understand it correctly?