Products > Test Equipment
Siglent SNA5000A two and four port VNA's
G0HZU:
I think the normal max input is -5dBm for that Ecal model if you want a decent calibration without compression effects.
I think that 10dBm is the damage level. Maybe (hopefully!) the Siglent VNA would be smart enough to turn down the RF level if an unwary operator tried to put 10dBm into the Ecal as this is right on the damage level for the Ecal.
At 26:09 in the video the VNA appears to be displaying about a 142dB range in places with 500Hz bandwidth (!) which doesn't seem likely even with 10dBm source power and 32 averages. So I'd suspect some issue with calibration or a bug in the system that makes the dynamic range appear much greater than it really is. Maybe this is caused by the attempt to calibrate at 10dBm. At 27:32 with the S31 measurement the noise floor is generally higher with the same settings.
tautech:
--- Quote from: TheSteve on August 30, 2022, 06:16:29 pm ---Maybe I need to re-watch the video but did we see Shahriar use his Keysight N4691B ECAL with the power on the Siglent turned up to 10 dBm? That is the absolute max power allowed for that model of ECAL, but anytime I use one with a Keysight VNA it will not allow power that high as ECAL performance is reduced.
--- End quote ---
You should take up this issue with Shahriar directly in the comments section below his video.
TheSteve:
--- Quote from: tautech on August 30, 2022, 09:02:45 pm ---
--- Quote from: TheSteve on August 30, 2022, 06:16:29 pm ---Maybe I need to re-watch the video but did we see Shahriar use his Keysight N4691B ECAL with the power on the Siglent turned up to 10 dBm? That is the absolute max power allowed for that model of ECAL, but anytime I use one with a Keysight VNA it will not allow power that high as ECAL performance is reduced.
--- End quote ---
You should take up this issue with Shahriar directly in the comments section below his video.
--- End quote ---
I don't usually post in the comments section of videos. Either way it would be nice to know if Siglent is going to support Keysight ECAL's that they aren't risking damage to them. Given the cost of the ECAL(quite likely more than the entire Siglent VNA) it is a pretty significant potential issue. And I did say potential, they may be reducing power during calibration. However generally turning the power up after a calibration adds additional error or invalidates it altogether.
tautech:
--- Quote from: TheSteve on August 30, 2022, 11:47:27 pm ---
--- Quote from: tautech on August 30, 2022, 09:02:45 pm ---
--- Quote from: TheSteve on August 30, 2022, 06:16:29 pm ---Maybe I need to re-watch the video but did we see Shahriar use his Keysight N4691B ECAL with the power on the Siglent turned up to 10 dBm? That is the absolute max power allowed for that model of ECAL, but anytime I use one with a Keysight VNA it will not allow power that high as ECAL performance is reduced.
--- End quote ---
You should take up this issue with Shahriar directly in the comments section below his video.
--- End quote ---
I don't usually post in the comments section of videos. Either way it would be nice to know if Siglent is going to support Keysight ECAL's that they aren't risking damage to them. Given the cost of the ECAL(quite likely more than the entire Siglent VNA) it is a pretty significant potential issue. And I did say potential, they may be reducing power during calibration. However generally turning the power up after a calibration adds additional error or invalidates it altogether.
--- End quote ---
100% which should also provide an Uncal warning.
There are some clues in the User manual E-Cal chapter starting on P90.
https://int.siglent.com/u_file/download/22_07_06/SNA5000A_UserManual_UM09050_E01D.pdf
Currently Rossenberger provide much of Siglent's high end RF accessories including SOLT Cal kits however for the coming 26.5 GHz models it seems only a mechanical Cal kit is to be available but they may be working on an E-Cal IDK.
27 GHz 3.5mm Cal kit
G0HZU:
I watched the whole video this evening and spotted that the top (RF) side of the board used for tracing the signal is actually the 'flipped image' rather than the bottom although it doesn't really matter.
I think a downconverter is used for the lowest part of the signal generation range and this probably covers something like 0-1.8 GHz. It is on this range where the performance seems to be degraded during the tests of the 4 port active device. I know the source power has been reduced to -30dBm but a typical lab VNA should perform much better than this in terms of trace noise and ripple for -30dBm source and 5 kHz BW. See the image below where I think an internal range change occurs at about 1850 MHz. Below this range change the performance seems to degrade a lot as it has a lot of ripple and noise. Above 1850 MHz the trace noise shows an instant improvement and looks to be as expected for -30dBm and 5kHz BW.
Also, at 29:11 to 29:12 in the video a couple of brief but suspicious trace blips occur in this 1850 MHz region. See the second image below. When a VNA changes range on the synthesiser the VCO has to jump to a very different frequency and settle correctly before the VNA can gather any s-parameter measurements. It looks to me that something isn't right about the lower range because of the noisy and ripply response and also because of the sporadic trace blips in this area. I don't think this can be blamed on a 'casual' calibration or 'lower return loss' as the performance suddenly degrades (badly) at a distinct part of the frequency range.
It could be caused by something as simple as a synthesiser/tracking error when used on the lowest range. This might be fixable in FW.
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