@rhb

How will you configure the correction for the Owon? Would it be possible to "import" corrections for other 12-bit scopes with high memory depth. This would be a great application for my 12-bit picoscope also.

Could the correction be something like recording the step response directly on the scope (without reflections) where your software uses some kind of convolution to correct for the scope ringing, phase and bandwidth limitations? Or is this a bit optimistic?

The process is as follows:

Window the recorded data so that you have a series of segments of the incident wave and a series of segments of the reflected wave.

Fourier transform each segment separately with adequate zero padding to prevent wrap around.

Compute the mean value of the phase by making a linear fit to the phase of each of the segment transforms and then averaging the phase delay. Correct each of the segments to the mean value of the phase. Then sum the segments at each frequency. Every doubling of the number of segments gives an additional 6 dB of dynamic range in the result.

Divide the summed complex series for the reflected wave by the summed value for the incident wave. Watch out for divide by zero or near zero. Then convert the result to the magnitude and phase of the DUT just as you would get with a conventional VNA.

Corrections for the DSO and the pulse source must be done via SOL or SOLT with a cal kit. The basic procedure is the same except for the cal kit you know the theoretical values for a cheap kit and measured values for an expensive kit.

My 11801 came yesterday, DOA. But reseating the boards and cables in the main cage got it working again, though I had to do it twice. It now runs the extended diagnostics and stops on an E5622 error which is bad NVRAM (dead battery). I've got replacements on their way from the UK. With a bit of luck I'll have one or more channels with a 23 pS rise time and 12.5 GHz BW. I also got an extension cable, so I can work on the sampling heads if needed.

Now I need to sharpen the pulse from Leo Bodnar's pulser so I can test the two SD-22 sampling heads I bought. The really hard part is being able to test an SD-32 head with 7 pS rise time and 50 GHz BW.

I'm considering a non-linear transmission line using a series of diodes for capacitors. I've not dug into the math yet as I'm having trouble printing Michael Case's 1993 PhD dissertation at UC Santa Barbara.

Generally this is more suited to fabrication in an IC, but I'm going to try using a piece of single sided PCB with the diodes standing on end and a wire running from the input SMA to the output SMA. The pulse sharpening is a consequence of the dispersion produced by the non-linear capacitance of the junction as a function of the applied voltage. I'll drive it with the 100 pS impulse unit I got from Leo Bodnar.

The really scary part is the price of a 2.4 mm RF connector to connect to an SD-30 or SD-32 head.