Forum Replies Created
- Posts
Hello Kaiser,
I’m glad to hear the SM200A is a better fit for your application.
There is overhead when using the queued sweeps for smaller spans (<1GHz). It sounds like you are getting around the best performance at that span. If you were willing to go to 300kHz RBW, you could get a bit faster sweep speed. See the attached image from the SM200A product manual that relates span and RBW to sweep speed. It should give you a good idea what kind of sweep speed you can achieve at various settings.
Based on the provided code, I think all the settings are being set to the optimal values for speed, except for maybe increasing RBW if you want to try that.
Let me know if you have follow up questions or comments.
Regards
Hello DJSbriscoe,
It sounds like you are prepared.
The big things to look out for are,
DC – which sounds like you have handled.
+20dBm max into the unit – Which the attenuators will help with, or an RF limiter can help.
Connecting an antenna – Having yourself grounded or having an RF limiter on the front end will help with connecting an antenna on the front end. High risk being static on the center pin into the unit.Regards,
AndrewSpike does additional processing per sweep that could be slowing it down a bit. You should measure the sweep times using the API for an accurate number to see if it would be adequate for your application. The BB60C doesn’t have any sweep queuing mechanism, so you incur the over head of processing and USB latencies for each sweep. 6-7 ms is probably the ball park for the fastest possible times.
We don’t have an SM200A demo/loaner program. If you are outside the US, your distributor might have a loaner program.
Regards
Kaiser,
As of right now, none of our devices have firmware support for triggered sweep acquisitions.
I don’t know the specifics of your application, but the SM200A has a 1THz per second sustained sweep speed, which means you could for instance sweep a 100MHz span ‘sustained’ (IE by queuing up sweeps) in less than 1ms. This would give you a 1ms or less resolution up to a 1GHz span for sweeps. I think this would be about the best you could do with standard sweeps and our devices.
Regards,
AndrewHi Kaiser,
You are correct to note that sweeps are not synchronized between devices. There are unknown latencies that exist such as USB timings/etc. We don’t have any mechanisms for synchronizing sweeps for our devices currently.
The traditional way to synchronize measurements for our devices is with the trigger input port in IQ acquisition mode. Aligning the spectrum measurement (FFT) on the IQ data after detecting an input trigger on each BB60C is the way to accomplish this type of task. As you correctly noted, the bandwidth would be limited to 27MHz at that point.
If you are measuring a pulsed signal and depending on your measurement, you may not even need an external trigger, you could simply look for a video trigger (specific amplitude level in the IQ data) and align on that.
While it doesn’t help your current situation, we are investigating a 160MHz IQ BW triggered acquisition for the SM200A.
We don’t have immediate plans to look into a triggered sweep measurement for the BB60C, but we do appreciate you sharing your use case. This can help us guide future development.
Regards
The scaling was changed to be more representative of the actual contribution to that bin. We had arbitrary scaling which was not consistent across all of our devices, so we changed it so that the scaling factor is ‘correct’, IE divide the number of hits in that bin by the total number of possible hits for that bin.
In general this resulted in a decrease of absolute values but will still plot the same if you increase the sensitivity of your coloring algorithm. That is what the slider does in Spike, it changes what is considered ‘full scale’.
I hope this helps,
Regards,
Andrew1) The sampling rate is 80MS/s IF which we convert to 40MS/s IQ.
2) Yes, we do overlapped FFTs. I apologize, 1.25 is not necessarily the exact number, it’s going to depend on the overlap amount. The idea being the same though, the energy needs to be present in a significant portion of the FFT to show up at the correct amplitude on the spectrum.
3) It depends on what you need from the measurement. This will also mean that the waterfall only has 30ms resolution, which some people might want a smaller resolution, in your case see activity in the waterfall between the pulses.Regards,
Hello Andrew,
You are correct in noting that the ADC overflow is not tied to the IQ samples. We would need to do a bit of work to make that happen.
Right now, the ADC overflow flag is a boolean that is cleared once per call to GetIQ. Setting purge to true will not clear it right now.
Until we change the behavior of the API, it might be appropriate to ignore the ADC overflow flag when you want to purge IQ?
I apologize for the inconvenience. I will make a note of this issue and in the future maybe we can improve the reporting of the ADC overflow flag.
Regards,
AndrewHello Bittware,
The maximum sample rate of the SA44B at the IF is ~486kS/s, which means a 5us pulse would only appear in ~3 samples. Generally in real-time modes, the energy of a signal needs to be present in 1.25 FFTs worth of data. In fact the Spike software even tells you the signal duration required for 100% probability of intercept (for the signal to be represented on display within 3dB). At the highest RBW, the 100% POI requirement of a signal is 592us. Once signals start becoming shorter than this, the energy level displayed will decrease.
In short, the SA44B is not the best tool to measure this type of signal using real-time mode.
What you can try, is using zero-span mode to capture the pulse in the time domain. A 5us signal can be captured in this mode. I have included a picture of this configuration with my SA44B. I used a 5us pulse with 80us period to demonstrate. The spectrum plot in the zero-span mode will still not be accurate, but you can get a good idea what the pulse looks like in the time domain.
The BB60C or SM200A would be better analyzers to measure this type of signal in real-time, the BB60C has a minimum 100% POI of 4.8us. As you have noticed though, the sweep time of our real-time mode is ~30ms and will also be that for the BB and SM. We accumulate ~30ms worth of spectrum before displaying the results in real-time which means you will see the accumulation of several pulses in your config in one sweep. At this point we are unable to have a finer resolution than this.
Regards,
AndrewMike,
Yes I think I know what’s happening.
The MATLAB example folder includes the bb_api.dll which is outdated. If you have a newer BB60C only the latest versions of the API will be able to be used. (The older API version can’t recognize your newer BB60C) In that same SDK, go to the core API folder and copy over the newest API.
I’m assuming you are running 64 bit MATLAB so I think you just need to copy over the 64-bit API and header, overwriting what is already in the MATLAB folder. Copy the contents from
signal_hound_sdk\device_apis\bb_series\win\lib\x64
into the MATLAB folder with these existing files.I look forward to your results.
Regards,
AndrewHi Charles,
Thanks for the feedback. I’ll look into this, or at least see if there is a quick way to add something to solve this. It may involve adding dummy or duplicate points. Unfortunately I can’t provide a timeline for this right now.
I appreciate the requests and feedback you have been giving us. I hope some of the added functionality has been of use to you.
Regards,
AndrewNolan,
The STREAM_IF flag has been deprecated and the DIRECT_RF flag has been superseded by our IQ streaming functionality. Both flags were from a time when we didn’t have IQ streaming functionality across the full operating frequency of the BB60C. Is IQ streaming adequate for your application? I do not believe we have any examples or documentation on the older two flags right now.
Regards,
AndrewHello Serpi,
The temperature read in Spike is the internal temperature of the device. The BB60C is not able to provide external temperature readings. When we calibrate the BB60C across temperature we use environmental chambers to control the external temperature.
Regards,
AndrewFor anyone who is seeing this same issue, the Ubuntu 18.04 BB60C .so file was corrupted. The .so file was re-uploaded in the SDK on 11-6-2018.
Marc,
I have sent you an email.
Ray,
Some other ideas,
1) Are you using a 32-bit OS? Our Linux APIs are compatible only for 64-bit OS’s.
2) Maybe try getting rid of all the soft links? Rename the main library to libbb_api.so and see if that resolves the issue.Regards
Hi Bittware,
I don’t have a timeframe for when SCPI support for zero-span would occur. I’m assuming triggering is an important aspect of your measurement? If so, then using the API directly to request IQ, trigger, and then FFT the IQ data to create the spectrum plot is the only alternative. Otherwise if you do not need triggering, then using SCPI with standard sweep mode seems like it would be adequate.
If you haven’t seen the APIs yet, you can find them on the SDK landing page.
https://signalhound.com/software/signal-hound-software-development-kit-sdk/Regards,
AndrewAndrew4010,
Yes, APIs with version 4.0.0 and greater support all BB60C/A devices. We don’t maintain download links for older versions of the APIs. I don’t believe the interface has changed between 3.1.1 and the current version so it should be a drop in replacement.
Regards,
AndrewMarc,
Can I ask what you mean by “could not get it to load USB drivers”? Did the driver installer fail to complete? Did you run it as administrator?
Check out the other troubleshooting tips on the Spike landing page in the FAQ under the question titled “The software reports device not found (for the SA44B)”
Particularly, if you have any anti-virus running (pre-installed on these PCs such as Norton/McAffe) either disable or uninstall if you don’t plan on using them. Also the “Load VCP” issue can cause the issue you are seeing.
https://signalhound.com/spike/
I look forward to your results.
Regards,
AndrewHi Dave,
Maybe other forums members will be able to help, I’m not familiar with parts outside what we provide. You also might have more luck on a dedicated radio forum.
Regards,
Andrew