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| Kirkby calibration kit alternatives? |
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| hendorog:
--- Quote from: suj on February 25, 2018, 06:56:22 pm --- --- Quote from: G0HZU on February 25, 2018, 05:51:58 pm ---...It's a shame this Lx correction can't be added to the 8753 firmware in some way. --- End quote --- By the way. It should be possible to do it off-line with Metas. It has a built-in driver for the 8753 and 8720 series (as well as 8510C, ENA, PNA). You can make measurements and off-line error correction using this software. Definitions of the "short" element that you can prepare have the option of defining L. The procedure is shown in the tutorial on the program's website. It looks like a Swiss army knife ::) --- End quote --- Bingo. I was thinking of using scikit-rf, but Metas would no doubt be more straight forward. Really looking forward to getting hold of it. |
| G0HZU:
--- Quote ---By the way. It should be possible to do it off-line with Metas. --- End quote --- Wow, that sounds great. I hope to get a copy of METAS soon :) See below for a quick and dirty OPEN and SHORT made from a pair of SMA F-F bullets. One has a commercial SC end cap for the short. Sadly, the two bullets are from different manufacturers so they are not going to be the same but the end cap for the short is a known part and it isn't expensive. Maybe $9? So maybe if I buy some Amphenol SMA F-F bullets from Farnell ($8 ea?) we could have a go at making a cheap cal kit for the masses? But for now, have a go with METAS to see how flat you can get the phase data for these two bad boys below? |
| hendorog:
I was having a heck of time with this one. The fit wasn't lining up with the Metas one by suj Then I found a bug in the model calculation for the Lx params. Fixed that and tada, now it lines up :) Although it does tend to find another result at 53 ohms Z0. This one took a bit of nudging. --- Code: ---Optimization results: offs_delay = 32.331122 ps offs_loss = 6.333923 Gohm/s offs_Z0 = 60.858025 ohm L0 = 872.429450 * 1e-12 H L1 = 5981.654164 * 1e-24 H/Hz L2 = 37028.127991 * 1e-33 H/Hz^2 L3 = 3160.750516 * 1e-42 H/Hz^3 Residual RMS error : -53.679006 dB --- End code --- |
| hendorog:
--- Quote from: G0HZU on February 25, 2018, 07:22:10 pm --- --- Quote ---By the way. It should be possible to do it off-line with Metas. --- End quote --- Wow, that sounds great. I hope to get a copy of METAS soon :) See below for a quick and dirty OPEN and SHORT made from a pair of SMA F-F bullets. One has a commercial SC end cap for the short. Sadly, the two bullets are from different manufacturers so they are not going to be the same but the end cap for the short is a known part and it isn't expensive. Maybe $9? So maybe if I buy some Amphenol SMA F-F bullets from Farnell ($8 ea?) we could have a go at making a cheap cal kit for the masses? But for now, have a go with METAS to see how flat you can get the phase data for these two bad boys below? --- End quote --- I did a bit of blue sky thinking: There is nothing preventing us from having different coefficients for different frequency ranges. The fit will be better by limiting the frequency range it is over. Also, if the cal is done offline in software, then changing coefficients (i.e. recalibrating using a different set of coefficents) is purely software and doesn't require another sweep. So it would be technically possible to do a full sweep and change cal definitions on the fly. The definitions would match the real cal standards very closely. In fact I expect this could be as good or better than a high quality cal kit - assuming it only has one set of coefficents for the entire range of the kit. Perhaps this is how the eCal units work? |
| suj:
--- Quote from: G0HZU on February 25, 2018, 07:22:10 pm ---But for now, have a go with METAS to see how flat you can get the phase data for these two bad boys below? --- End quote --- Two cases for the "open" element and two for the "short" element. For each element once Z0 opened and once set to 50 \$\Omega\$ --- Code: ---Agilent Definition Standard Type: Open Offset Z0 (Ohm): 60.711892 Offset Delay (ps): 27.289762 Offset Loss (GOhm/s): 3.507799 C0 (E-15 F): 414.232256 C1 (E-27 F/Hz): -6871.633507 C2 (E-36 F/Hz^2): -4959.099088 C3 (E-45 F/Hz^3): 470.623016 Agilent Fit Error RMS Error 0.001900 Max Error 0.003349 _______________________________________________ Agilent Definition Standard Type: Open Offset Z0 (Ohm): 50.000000 Offset Delay (ps): 58.437897 Offset Loss (GOhm/s): 2.711473 C0 (E-15 F): -304.566047 C1 (E-27 F/Hz): -8873.121112 C2 (E-36 F/Hz^2): 2622.781977 C3 (E-45 F/Hz^3): -343.691735 Agilent Fit Error RMS Error 0.002197 Max Error 0.003648 _______________________________________________ Agilent Definition Standard Type: Short Offset Z0 (Ohm): 56.059063 Offset Delay (ps): 41.557996 Offset Loss (GOhm/s): 3.717653 L0 (E-12 H): -222.842514 L1 (E-24 H/Hz): -19759.249841 L2 (E-33 H/Hz^2): 11091.105982 L3 (E-42 H/Hz^3): -651.849387 Agilent Fit Error RMS Error 0.001378 Max Error 0.003844 _______________________________________________ Agilent Definition Standard Type: Short Offset Z0 (Ohm): 50.000000 Offset Delay (ps): 32.074189 Offset Loss (GOhm/s): 4.973737 L0 (E-12 H): 492.787861 L1 (E-24 H/Hz): -6736.857074 L2 (E-33 H/Hz^2): -3868.927304 L3 (E-42 H/Hz^3): 506.666193 Agilent Fit Error RMS Error 0.001556 Max Error 0.004609 --- End code --- Open element, Z0 open: Open element, Z0=50 \$\Omega\$: Short element, Z0 open: Short element, Z0=50 \$\Omega\$: |
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