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The SA44B / TG44A with coupler can be used to measure magnitude S11 and magnitude S21. It cannot provide the phase of S11 or S21. This is the critical difference between a VNA and SNA.
A two port VNA can also provide S22 and S12 without swapping your device around.
The best way to mute the output is to set the frequency to 0 Hz, amplitude to -30 dBm.
Eduk,
We have observed, when the preamp is used, at 0 dB of attenuation, it can take a long time for the DC blocking cap to reach steady state (up to 30 seconds). Typically, setting your reference level to -30 dBm briefly (preamp on, attenuator 5-10 dB), before proceeding to maximum sensitivity, allows quick settling.On a fraction of units, the preamp’s DC blocking cap never reaches steady state without a better DC path to ground. We typically have to add a 2.2k resistor to help bleed this off. You can contact us for a warranty repair if your SA44B is exhibiting this behavior. I apologize for the inconvenience.
We will be updating the design to add this resistor in the near future.
The SA44B definitely has some shortcomings when it comes to EMC testing. It relies on a software image rejection algorithm to get rid of both image responses and its own spurious responses. This algorithm tends to work better on sparse spectrum with narrow RBWs, where the chance of a spur and an image overlapping is low. When there are many signals closely spaced, especially at low frequency where there may be higher frequencies present mixing with harmonics of the LO, the chance of spurious signals overlapping on the primary and image sweep are high.
This is one of the reasons we strongly recommend the BB60C for EMC work. With hardware image rejection and specified spurious performance, you get reliable EMC sweeps.
We aren’t going to IWCE, but we will be at IMS in June.
If you’re building CW / FM waveforms in excel, you can generate the instantaneous phase data, and then use the sin and cos functions to convert to I/Q data.
The .csv file is generally for non-standard waveforms. Our API can be used to control the VSG without the GUI.
The CSV file can be used if you have less than 2048 I/Q samples you wish to send, either as a repeating burst, or a continuous loop.Jaguirre,
From a hardware standpoint, the SA44 does not have a preamplifier, so the noise figure is much higher. It also has more spurious and residual signals than the SA44B. But it should run in our Spike software. There are additional RBW / VBW limitations for the SA44 as well, for spans larger than 200 kHz.Eduk,
The SA44B works by capturing 200 kHz patches of spectrum and processing them. There seems to be some 200 kHz periodicity. I noticed that the peak-to-peak periodicity improves for the stronger signal, so it looks like what you are seeing is the IF filter shape on the SA44B’s noise level.Because your RBW is 100 kHz, the software has a hard time correcting for IF flatness. If you reduce your resolution bandwidth to 30 kHz, the software will have an easier time correcting the IF flatness, and this ripple should be reduced.
The SA44B requires 480 MBPS USB (high speed USB 2.0). It also requires about 400 mA of current from the port. If the isolated hub cannot provide the data rate and required power, it would not work. Otherwise it should be fine.
February 1, 2017 at 9:31 am in reply to: HowTo Correct UNCALIBRATED Label on Tracking Generator Sweep Display The “uncalibrated” indicator means that a valid “store thru” has not been performed, or a setting was changed after it was performed, invalidating it.
If you set the desired center frequency, span, and reference level, select the appropriate scalar network analysis settings, and then store the thru, this indicator should remain off until you change a setting.
Hopefully this helps.
Jason,
The biggest issue is that the ARM architectures we have tested cannot stream I/Q data at the full data rate, so there are RBW / VBW limitations. Additionally, FFTs take much longer, so on the ARM architecture we do the minimum number to satisfy the settings.
For better performance, something like an Intel Atom processor gives you the full SA44B performance at lower power consumption.I’m sorry you had a hard time with the drivers. Lately, many customers have had to un-check the “Load VCP driver” check box, but that is usually the extent of the driver problems.
If this happens again, there is a second possibility. If the SA124A has trouble booting or rebooting, there is a small FTDI settings patch I can send you that might help.
I have not seen this problem before, but your VSG should still be covered under warranty. Contact support@signalhound.com and we can set up an RMA for repair. I apologize for the inconvenience. If you bought it from a distributor, contact them for a repair or replacement unit.
Amy,
It is unusual to require more than 2 digits after the decimal for dBm readings, especially for small signals, where noise is going to dominate the reading. What type of analysis are you doing that requires that much precision? I would worry that our analyzers would drift more than this each reading.
December 24, 2016 at 7:56 pm in reply to: SA44B no carrier w/ < 300 KHz span unless ext. 10 MHz is selected This is definitely not normal. Is this the Spike application? Have you tried restarting it? If the problem persists, you may need an RMA for repair.
It looks like maybe the phase of your I/Q data doesn’t match up. Is this what you are seeing?
You should not expect the phase of two demodulated signals to line up. Even if the BB60s use the same external trigger and external time base, there is still a fractional-N PLL that can lock to several different phases each time you change the LO frequency.
Multi-channel phase coherent receivers exist, but they are generally more expensive.
If you need to make phase coherent measurements with two BB60Cs, generally you would:
1) Use a common external 10 MHz reference to align frequency
2) Use a common trigger to align time within 50 ns.
Now, all that is missing is phase alignment, and this is where it gets tricky.
3) Select your frequency on both devices, and begin streaming I/Q data. Do not change frequencies or interrupt the I/Q data stream for the next steps.
4) Send a known signal to both devices to calculate a phase offset (and possibly amplitude offset if needed) between devices
5) Connect your unknown signal. You can now measure relative phase between the two streaming devices, until you change frequency or the I/Q stream is interrupted.Ramin,
At this point we do not have a software interface to automate Spike’s EVM measurements, but it is something we have talked about, and may eventually add.
Right now, you’d have to choose between reading the Spike software EVM manually, or using the API to capture I/Q data and something like Matlab or LabView (or other library) to compute EVM.James,
If you rig it up such that the CPU fan blows across it, this may help keep it cool. It needs to dissipate about 6 watts, so if you insulate it too much the internal temperature will rise further. Some customers have mounted it to a metal plate, which can conduct heat away from the BB60C and provide more square inches for cooling…If it were a TG124, one might further observe above 4 GHz, ‘M’, 0x02, 0xC0, and then dropping below 4 GHz, M, 0x01, 0xC0.