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| Kirkby calibration kit alternatives? |
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| G0HZU:
Probably the most controlled way to try your experiment is to see if you can generate Cx coefficients for the Kirkby kit OPEN s1p file posted below. Then post up your Cx values here and I'll see how they perform in terms of flattening the phase? Will I see the same flat result as in post #47 for example? |
| hendorog:
--- Quote from: G0HZU on February 24, 2018, 03:38:39 pm ---Probably the most controlled way to try your experiment is to see if you can generate Cx coefficients for the Kirkby kit OPEN s1p file posted below. Then post up your Cx values here and I'll see how they perform in terms of flattening the phase? Will I see the same flat result as in post #47 for example? --- End quote --- Will do. I will need to setup the NLopt stuff first for the script to work. I had it setup in the past but it must have been on the laptop which died on me. |
| G0HZU:
How long does it take to run? I've added some auto optimise limits in the RF simulator to see if it can do a better/faster job than me. For my open and short I tweaked the Cx and Lx coefficients manually whilst looking at the phase. It took a minute or so to get it quite flat. With this attempt at an auto optimiser I gave it a 'bad' starting point with the phase deliberately bad and so far it hasn't managed to beat my manual attempts and it seems stuck in a rut. I think I need to tweak the optimiser a bit... |
| hendorog:
--- Quote from: G0HZU on February 24, 2018, 03:38:39 pm ---Probably the most controlled way to try your experiment is to see if you can generate Cx coefficients for the Kirkby kit OPEN s1p file posted below. Then post up your Cx values here and I'll see how they perform in terms of flattening the phase? Will I see the same flat result as in post #47 for example? --- End quote --- Ok here is the output of the first successful run. I can see C1 has hit its limit so not expecting much... I didn't change any of the defaults for the initial settings. I suspect I will need to give it an accurate offset delay. It took several minutes, but I didn't hang around to watch. I was out of the room for 10 minutes or so. The installation of NLopt is pretty painful. There was a identifier which had changed (Octave_map vs octave_map), and some messing around with include paths etc. Attached are the graphs it produced, and below is the final output. --- Code: ---1st optimization ended with status: Optimization stopped because xtol_rel or xtol_abs was reached. (NLOPT_XTOL_REACHED) 2nd optimization ended with status: Generic success return value. (NLOPT_SUCCESS) Optimization results: offs_delay = 50.000000 ps offs_loss = 5.000000 Gohm/s offs_Z0 = 50.000000 ohm C0 = -172.920826 * 1e-15 F C1 = 10000.000000 * 1e-27 F/Hz C2 = -1238.347686 * 1e-36 F/Hz^2 C3 = 19.888550 * 1e-45 F/Hz^3 Residual RMS error : -47.880563 dB --- End code --- |
| hendorog:
Second run - I opened up the limit for offset delay, as the first run had hit the limit of 50ps. This completed in less than 1 minute: --- Code: ---?1st optimization ended with status: Optimization stopped because xtol_rel or xtol_abs was reached. (NLOPT_XTOL_REACHED) 2nd optimization ended with status: Generic success return value. (NLOPT_SUCCESS) Optimization results: offs_delay = 55.447558 ps offs_loss = 5.000000 Gohm/s offs_Z0 = 50.000000 ohm C0 = -265.965357 * 1e-15 F C1 = -2793.805192 * 1e-27 F/Hz C2 = 1240.335578 * 1e-36 F/Hz^2 C3 = -194.306089 * 1e-45 F/Hz^3 Residual RMS error : -53.982524 dB --- End code --- |
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