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DDR,
You should not have big dropouts like that. This would indicate either hardware failure, bad correction data, or possibly bad sweep settings resulting in bad measurements.
To rule out the sweep settings issue, please test individual failing points with the VSG in CW mode, and the SA124B set to a 200 kHz span centered at the output frequency. You can email support at signalhound dot com and we can try to figure out if we can fix it with correction data or if we will need to repair one of the units.Serpi,
If you select average, power units, there is no 2.51 dB correction. This only applies to log averaging. Our DANL spec is worst case. NF is usually calculated off of typical DANL. You can use the noise marker with a reference level of -50 dBm, input terminated, at the frequencies of interest. Then add 174 to calculate noise figure of your actual unit.Hiroshi,
Yes, you can Store Thru and Store 20 dB pad, both with the 20 dB pad in place (leave the 20 dB pad in place for testing). This will enable high dynamic range sweeps, with 20 dB additional gain available.Hiroshi,
I’m glad you like it!
1. Yes. Remove the 20 dB pad after it has been measured. We use the 20 dB pad to measure both high gain and low gain and compute an internal offset.
2. Make sure you don’t exceed +20 dBm into the SA44B. You will need to compensate your measurement for the additional gain after the store thru, but otherwise it should work just fine.Please note that the BB60C or SM200B/C will provide lower EVM numbers for a clean GSM signal, as I believe it barely fits in the SA44B bandwidth so there is significant rolloff at the band edges.
Stanley,
There are two major factors that affect the accuracy and stability of scalar measurements:
1) The stability and phase noise of the TG
2) VSWR
There isn’t a lot you can do about the TG, but adding 3-6 dB fixed SMA attenuators on the output of the TG and the input of the SA and keeping them there for both the thru measurement and the DUT measurement can improve measurements quite a bit by reducing VSWR.Michael,
I suppose if you had a 2-channel oscilloscope, and used the API, you could stream data out of both with embedded triggers, use the scope (programmatically using SCPI) to calculate the time delta, and then add or skip the appropriate number of samples on one channel. You’d want an external 10 MHz reference to tie them together as well.It’d be a bit of a project… a 2-channel VSG or SDR would be a more straightforward answer.
Jim,
We typically see 1.2 amps, but depending on mode and input voltage, 1.3 amps would be at the high end of the normal range. About 1/2 of the power draw is from switching regulators, the other half from LDOs, so current can be a little higher if the voltage is lower.Michael,
The USB data comes back as packets with header and trailer data. If the software cannot “frame” the data such that the headers and trailers are where they’re supposed to be, you get this error.
Power cycle the BB60C, maybe try a different USB port, and let us know if the problem persists.Mcline,
If you look in vsg_example_complex_freq_hopping, you’ll see vsgSubmitIQ(). You could output a trigger pulse by adding vsgSubmitTrigger(). The API sends them to the VSG in the order received. So if you Submit some I/Q data, then submit trigger and then more I/Q data, the trigger’s rising edge will match the first sample of second chunk of I/Q data.It looks like you’re missing a scale factor on the I/Q data, and phase wrapping math on the FM plot.
DDR,
If a 30 MHz high pass filter would not affect the signals you need to produce, the VSG60A will probably work. Otherwise, you’ll need a dedicated arb / function generator instead.Unfortunately we do not support USB 2.0 speeds with the SM200B. While I can see the benefit of the convenience, the capabilities would be tremendously reduced at USB 2 transfer speeds, and it would be a very large firmware change, so we opted not to add the support at all.
Yes, we can’t stream (gap free) more than 170 MHz of bandwidth without a lot more paperwork. We can’t frequency mask trigger on more than this either. But for short captures followed by gaps, it is my understanding that the same rules don’t apply. That being said, I don’t think we will allow the filter to be disabled, but future products will probably have more filtering on the FPGA to avoid this video triggering on strong signals outside the bandwidth.
This sounds like perhaps a moving average filter before video trigger would work. We have talked about adding this feature. I’ll chat a bit with the team and see what they think.
I can speak to the signal path portion. When your sample rate exceeds 61.44 MSPS, the video trigger moves from the API to the FPGA. It triggers on the amplitude of the raw 250 MSPS data, before the digital bandpass filter is applied. There is significant rolloff beyond the 160 MHz point, but triggering can still occur. The thought was if you are video triggering on a signal contained within the 160 MHz bandwidth, it would be transparent to the user, but energy just outside the 160 MHz bandwidth is the exception.
This was resolved in the SM200C, since we filter and resample more aggressively on the FPGA and trigger on the PC, but I realize this doesn’t help you.
Hysteresis: I would love to hear more about what you had in mind, and if you can give us a use case. More advanced triggering is something we have talked about and would like to explore. Obviously there are a lot more options at the API level than the FPGA level.
We don’t have a good solution for a high dynamic range VNA. If you need to measure gain up to 75 dB (without phase information) you could use our TG + SA or BB, plus 60 dB of external attenuators.
We do not currently carry noise sources. You can look at Keysight’s 346A or B or Noisecom’s NC346A or B. I would recommend a 346B (or NC346B) for most testing, and if your gain is too high, pad it down at the output to around 20 dB for best results. The higher ENR generally provides better measurements, but not if you saturate your RF input.
Jan,
If you use Arthur’s suggestion, a parabolic phase relationship gives you the best dynamic range.