Digilent Analog Discovery* or (Digilent Products) for RF Power Calibration of B200-B210 SDR?

[dr.whom]

Hi!  I'm new to the forum, and I'm trying to find VISA-compliant RF power calibration hardware for my Digilent B200/B210 SDR units (for a lot less than 10,000 USD :-) ).   

Notes:

1. I'd prefer Digilent equipment if possible: I like the quality of my Zybo Z7, and I'm impressed that my recently-purchased Digilent B200/B210 units are much better build-quality than my older NI-branded B200 and B210.
2. Constraint: I don't do Windows (anymore).  I prefer to work on my MacStudio (arm64) and also have Ubuntu (& other Linux) (amd64/x86-64) boxes.
3. I like Waveforms based on running it in Demo Mode, but haven't purchased Analog Discovery * HW because I'm not yet certain if it can do what I need.

What I'm looking for:

1. VISA-compliant Calibrated RF Signal Generator, 800MHz - 7GHz. (low power: B2x0 max RF input power is -15dBm)
2. VISA-compliant Calibrated RF Power Meter, 800MHz - 7GHz.  (low power: B2x0 max RF output power is 20dBm) 
3. The link here describes VISA-compliant SW/Driver from Rohde & Schwarz - it also shows and describes the NI VISA SW/Drivers.  Functionally, the main difference between the R&S driver and the NI driver is that R&S works on Win/Linux/Mac, whereas the NI driver is Win-only.
4. Here's the Digilent product page for the B210 SDR if you're not familiar.

Does anyone have recommendations for the best/cheapest products (or combinations of products) to use?  

Here are some relevant excerpts from the docs for RF Calibration of the Digilent/NI/Ettus B200 and B210 SDRs (source):

Quote

In order to calibrate the transmit power, a calibrated power meter is required. To calibrate the receive power, a calibrated signal generator is required.  ...

The [usrp drivers] tool will control both the DUT (i.e., the USRP that is to be calibrated) as well as the measurement device (power meter or signal generator). UHD ships with some drivers for measurement devices, but can be extended for others easily (see Extending the calibration utility for custom drivers).

In order to run a calibration, the measurement device and the DUT need to be connected to the host PC on which the calbration measurement is performed. The following command will calibrate a B200 transmit power using a VISA-based power meter:

```bash

uhd_power_cal.py --args type=b200 -d tx --meas-dev visa

```

 ... [same thing for receive power, except use `-d rx` in the script params] ...

Kinda hoping Digilent has a solution, being the manufacturer of B200 / B210 ...

[JColvin]

Hi @dr.whom,

I'm slightly surprised that you find the Digilent sold B200/B210s of better quality. My understanding is that Digilent is just, more or less, a different distributor for these boards, or at least I am not under the impression that we manufacture them as opposed to NI, or at least I have been told that the boards are identical. I might be wrong on that though, I'm not tied in to manufacturing side of things and it's been awhile since I've looked into it.

Regardless, Digilent unfortunately does not have RF Signal Generators or Power Meters of any kind.

I would personally, and have been recommended by Ettus team to, reach out to the Ettus mailing lists, https://kb.ettus.com/Mailing_Lists, where Ettus Research engineers, Ettus support, and customers themselves have been active for the last 10+ years to find out what signal generator or power meter they would recommend.

If anything, this will at least reduce the time it takes for you to receive an accurate response since the Digilent staff will end up reaching out to the Ettus team about this anyway and echoing the answer back to you.

Thanks,
JColvin

[dr.whom]

(race condition: this was written at the same time as @JColvin's answer above) 

UPDATE: I did some research, and I think the answer to my own question is:

No, Digilent does not currently make what I'm looking for.  But should.

1. A 'good' VISA-API (USB-TMC) power sensor for 0.5GHz-8GHz RF costs about $5000. 
   1. A 'crappy' one costs $2500.  Punchline: both are the size of a USB thumb drive.  
   2. There are $200 VNAs for sale on Amazon that use USB-CDC to provide 200MHz-6GHz RF power measurement.  Gonna try that first.
2. Digilent products such as Analog Discovery (*) appear to communicate with Waveforms via the (USB-CDC) protocol rather than VISA/USB-TMC. 

If Digilent could do for $5000+ RF calibration / VNAs / SpecAns what they've done for Oscilloscopes with the Analog Discovery Series, that would be a good thing. 

... and it would be a good match for the USRP SDR product line.

Notes on USB-TMC vs USB-CDC protocols, courtesy of the always-infallible GPT-4:

Quote

USB-TMC (USB Test and Measurement Class) and USB-CDC (USB Communications Device Class) aren't directly comparable in the way you might think regarding bandwidth because they're more about defining how devices communicate over USB rather than setting speed limits. 

USB-TMC is tailored for test and measurement devices (like oscilloscopes and multimeters) to facilitate communication between computers and instruments. It's more about ensuring devices adhere to standards that make it easier for them to communicate measurement data and commands back and forth. It's not about speed; it's about compatibility and ease of integration into systems like LabVIEW, MATLAB, etc.

USB-CDC, on the other hand, is a broad category that includes several sub-classes for different types of communication devices, including virtual serial ports, ethernet control, etc. It's often used for simpler devices that emulate serial ports over USB, like some GPS units, modems, and serial converters. The actual data rate you'll see with USB-CDC depends on the underlying USB standard it's operating over and the efficiency of the device and host implementation.

 

Edited March 20 by dr.whom

[dr.whom]

1 hour ago, JColvin said:

@JColvin wrote:

I'm slightly surprised that you find the Digilent sold B200/B210s of better quality. My understanding is   ...    been awhile since I've looked into it.

Me too, for the same reasons...  I bought a new B210 when they came back in stock at Digilent in Feb - previously, I bought one in late 2020/early 2021 from NI.  Big difference.  However, the price has doubled in the interim - that might be a factor :-) 
 

Quote

Regardless, Digilent unfortunately does not have RF Signal Generators or Power Meters of any kind.

Yes I think we were composing replies at the same time - I suggest there's a market gap between the $5000 dongle and $200 VNA  :-) ...

Quote

I would personally, and have been recommended by Ettus team to, reach out to the Ettus mailing lists, https://kb.ettus.com/Mailing_Lists, where Ettus Research engineers, Ettus support, and customers themselves have been active for the last 10+ years to find out what signal generator or power meter they would recommend.

I shall ...

Thank you @JColvin.