NiUSRP 1.2 / USRP N210 / beat frequencies LO

Hi,
I made a Labview 2012 program based on some examples of the ni USRP 1.2 software, for being executed in my USRP N210. The objective of my program is to measure a signal, that right now is generated by a RF signal generator, after doing an fft plot of it, and show it in a graph chart. I also want to show a plot with the values of the max in dBs of the signal and its contiguous bins. The problem that i have is that i have some type of 'continous' signal that doesnt let me focus on the one signal that i want to measure and work with. I have read about some type of beat frequencies generated by the LO of the USRP n210 motherboard, but im not completly sure about that. I also want to note that i have the tvrx2 daughterboard installed. Any question, answer or recomendation will be very welcome! Thanks
Santiago Mariño Cambeiro
Attachments:
IMAG0417.jpg ‏1090 KB
niUSRP EX Rx Continuous Async v1.vi ‏92 KB

Hi Santiago,
Most likely what you are observing is the so called "LO leakage".
A typical workaround is to shift the LO frequency outside the frequency band that is monitored, keeping
in mind that you are restricted by the A/D bandwidth (check out
the USRP property node for an item called LO Frequency [1]).
As a side node, regarding your application, I've seen that you are using a laptop.
Be aware that the achievable sampling rate depends on the "quality" of the embedded NIC and the driver
parameters (it all depends on the bandwidth you are targeting).
L
[1] http://zone.ni.com/reference/en-XX/help/373380B-01/usrppropref/pniusrp_lofrequency/

Similar Messages

How to isolate the signals between TX/RX and RX2 on the USRP N210?

Hello everyone,
I want to use one USRP N210 to transmit and receive signals simultaneously. But when I try to transmit signals from TX/RX and receive signals from RX2(the transmitted and received signals are on the same center frequency), I found that the there are signals leaked from TX/RX to RX2. What can I do if I want to isolate the signals between TX/RX and RX2?
Thanks very much!

Hello -
I believe two questions are being asked on this thread:
1. Isolation: The internal switch provides about 30dB of isolation between TX/RX and RX2. As with most transcievers, if you transmit and recieve on the same frequency at the same time you will recieve your own transmission as well.
2. Spurs: The USRP represents and optimized price vs performance and some images and spurs will occur. Often they can be predicted as you mention. One thing you can do is use the CORDIC to acquire a signal at IF and then digitally shift I and Q to the ceneter frequency and bandwidth of interest. This is done by setting the 'lo' via a property node and 'center frequency' to different values.
Other NI RF instrumentation options are available if you're looking for RF performance. The NI 5791 was recenty released and may be of interest.
Best Regards,
Erik

USRP N210 WBX phase offset did not remain constant

Hello,
Following is anouced;
After tuning the RF front-ends, each local oscillator may have a random phase offset due to the dividers in the VCO/PLL chains. This offset will remain constant after the device has been initialized, and will remain constant until the device is closed or re-tuned.
However,
I found the phase offset did not remain constant for some USRP N210 with WBX in for USRP N2x0 receivers synchronized system for 20 minutes.
I am trying to build phase synchronized measurement system using USRP N200 x 2, N210 x 2 OCTOCLOCK .
ch1 and ch2 is connected with MIMO cable
ch3 and ch4 is connected with MIMO cable
ch2 and ch4 is connected OCTCLOCK wiith 10MHz and PPS.
All inputs were coupled to SG not sincronized output.
attached screen shot shows the results observed for 200 minutes. .
Right end Plot shows drift of phase offset during 200 minutes ; white line is ch2-ch1 , red line is ch3-ch1, green line is ch4-ch1.
It seems each MIMO pair has kept the same phase offset but diffreent MIMO pairs.
Is this expected results?
Below is the configulation in LabVIEW Block diagram.

Edit time expired, trying again with a complete response.
The antenna selection changes the front-end switch on the WBX/XCVR boards. The Basic boards do not have a switch. They are both directly sampled as I and Q respectively. Therefore the antenna selection parameter is not used with those boards. Use property nodes rather than the single config block to configure the device parameters.
Secondly there is a known issue with LO lock, speficically that the driver expects one and the low frequency boards don't have them . At the time of release only the XCVR2450 and WBX were tested as stated in the Readme. NI is planning to release an updated driver in the next week or so that address this and adds other functionaity.
Regarding the SBX, it has been tested in the coming driver update as well.
Regards,
Erik

Connecting two USRP N210 to one computer

Hi,
I am trying to connect two USRP N210's to one pc. I want to simulate a real-time communication p2p link and I must use some blocks which are only available in MATLAB Simulink, i.e. I will have to configure one USRP as transmitter and the other as the receiver and in the middle I will put some Simulink blocks. My question is very basic. How do I get the operating system/ MATLAB, etc. recognize both of them, i.e. the two different IP addresses. I wonder I should use a network card with two slots or two normal network cards? or is there a simpler solution?
FYI: I am very new to USRP's.
Thanks,
Reza

Dear Reza,
Two possibilities : (a) use the so-called MIMO cable or (b) use two network interface cards.
In both cases, USRPs are differentiated through their IP adresses.
I'm not using Matlab so I'm not sure whether (a) works in this environment. Solution (b) will work.
Also note that for real-time processing our experience tells that the
quality of the NIC+driver makes a difference.
Best wishes
L

Can I change the HDL for the USRP N210 FPGA to use only I part of data, not I/Q

Hi all,
While using the USRP N210, we've run into a slight roadblock. We're using UHD's rx_samples_to_file and are able to receive at 20 Msps for 2 minutes using 8-bit complex integer (sc8) over-the-wire format without dropping any samples, but we'd like to receive at a faster data rate, preferably using 16-bit complex integers. We don't really need the Q part of the data, just the I part. So, in addition to using a faster hard drive for the computer and (if we have to) sacrificing half the data bits (using sc8 instead of sc16), we thought about altering the HDL code to only use the I part of the data to help us increase the data rate.
Is this even possible/plausible? How would you suggest going about accomplishing this? Ultimately, our goal is to receive at a faster data rate. Do you have any other ideas?
Thanks for your input

Hi mgarey,
While you may find some other UHD users in these forums who can help the best bet is probably to send your question to [email protected] since they are much more experienced in UHD troubleshooting. I don't think you'll be able to edit the FPGA itself but there may be a way to pull back just the I data, I can't say I've tried either one myself though.
Best Regards,
Peter W.
RF PSE

How to switch central frequency fastly with labview and USRP?

Hello everybody,
         Recently I was making a frequency hopping receiver with labview and USRP N210 and SBX. The transmitter works on the 2.4G band, and it changes from one central frequency to another every 65536us. As I think, if I start receiving at the correct time, and change the central frequency of the USRP every 65536us, I should be able to receive the data.
    But I find that, when usrp switch form one central frequency to a different one, it spends nearly 48ms and when it switch from one frequency to the same one, it only spends 3ms(I test the performance by modifying the niUSRP EX Rx Continuous Async Reconfig on the Fly.vi example). So if I want to follow the hopping sequency, I may can only receive 17ms data because I have to save time for switching central frequency.
     My problem is that: why usrp changes central frequency so slow, how can I make the process faster? If I want to follow the hopping sequency, can anybody give me some good advice? Thanks

There is an attribute "LO Frequency" that you can use to lock down the frequency of the local oscillator. Then, when you set the "Carrier Frequency" attribute, the difference between the carrier frequency value and the LO frequency value will be realized by frequency shift in the DSP in the FPGA. Changing this "digital" frequency shift value is much faster, since you don't have to re-tune the local oscillator.
Let's say you're sweeping from 2.44 GHz to 2.46 GHz. Set the "LO Frequency" to 2.45 GHz then Commit. Then, in your loop, program the "Carrier Frequency" attribute from 2.44 GHz to 2.46 GHz. In the loop, it will only program the digital frequency shift, which will happen much faster.
Another tip is to use the property node to program only the attributes you want to change, rather than the niUSRP Configure Signal.vi (which sets many at once).
For more details, see the "Configuration:Advanced:LO Frequency Property" in the NI-USRP Help, and look at this example:
<LabVIEW dir>\examples\instr\niUSRP\niUSRP EX Fine-Tune LO Frequency.vi

TX and RX on N210

Hi
I am a new user of USRP and GNU Radio.I want to transmit and receive signal at the same time on USRP N210 but while doing this I am getting a timeout error
Traceback (most recent call last):
File "/home/ubuntu/Desktop/top_block.py", line 78, in <module>
    tb = top_block()
File "/home/ubuntu/Desktop/top_block.py", line 52, in __init__
    channels=range(1),
File "/usr/local/lib/python2.7/dist-packages/gnuradio/uhd/__init__.py", line 116, in constructor_interceptor
    return old_constructor(*args)
File "/usr/local/lib/python2.7/dist-packages/gnuradio/uhd/uhd_swig.py", line 2479, in usrp_source
    return _uhd_swig.usrp_source(*args)
RuntimeError: LookupError: KeyError: No devices found for ----->
Empty Device Address
I have attached my TX and RX code. Is there something that I am doing wrong in the program.
Thanks,
Ninad Regundwar
Junior Engineer | ARAV Technologies | www.aravtech.com
Attachments:
Files.zip ‏3 KB

Hey Ninah,
For GRC specific questions, you will get better support using the USRP/GNURadio mailing lists. This forum is targetted at providing support for USPR user using LabVIEW and the NI-USRP driver. You can find the mailing lists here: http://gnuradio.org/redmine/projects/gnuradio/wiki/MailingLists
It looks like you did not provide an IP address/device name for the USRP that you are trying to communicate with based on the error message below. You can find the IP address by running uhd_find_devices. Make sure your IP address is set to static, or else you will not be able to find your device.
Sarah Y
SDR Product Manager
National Instruments | Ettus Research

Ettus research N210 - NI Labview driver

I am using the Ettus research USRP N210 with LFTX/RX daughter boards. I was informed by NI representatives that it is compatible with labview if I download the NI driver software. I need assistance accessing the driver software and the installation procedure. Thank you.

Hey!
I got an N210 from Ettus and the SBX daughterboard. My intention is to use LabVIEW with that. I used the NI-USRP configuration utility to burn the FPGA and firmware images, but the device will simply not send anything. According to what Erik replied to the initiator of this thread it might be necessary to use property nodes to configure the USRP, but it holds for LFRX/TX or the BasicRX/TX.
Is it possible that it holds for the SBX as well? If not, could you please suggest what might be wrong? As of now I have notbeen configuring the settings by using property node, because I don't know if it is obligatory with SBX board.
Thanks,
Filip

Difference between NI-USRP and UHD

Hello
My project goal is to develop both the driver code for a custom daughterboard and a Labview vi control panel to modify the daughterboards properties.
I have been developing the UHD in Linux to include support for the daughterboard follwing the format of the existing Ettus boards. This all works fine in conjunction with GNU radio/GRC.
Now that I am trying to develop a Labview application to control the board I have had to move away from Linux as there is no Labview support for the USRP in Lunix.
I am just getting going here with Windows and am about to install the NI-USRP support package for Labview.
I am concerned this is a dead end though. What is the NI-USRP? Is it a wrapper that allows Labview to interface with the UHD API? Or is it an alternate driver to the UHD?
I was planning on building the UHD in windows to including the patch I have made for our daughterboard and then develop a higher level control system in Labview. In my reading thus far however, it looks as though the NI-USRP doesn't talk to the UHD, it is a self contained driver with it's own hardware support. If the UHD and NI-USRP are mutually exclusive, how am I going to build the NI-USRP from source? (assuming it is proprietary code)
More generally I could phrase my question as: How do I develop driver support for my daughterboard such that I can use it with Labview?
After-all, I understood one of the major purposes the USRP is sold for, is to enable daughter board development. It stands to reason then that it should be possible to use NI's development environment?
Any advice on what I need to install/acquire to set up a:
Labview -> driver -> USRP -> custom daughterboard
development environment would be greatly appreciated.
Alex
Solved!
Go to Solution.

Thank you for your response. Perhaps, myquestion was unclear, I did not mean to ask if NI-USRP was replacing UHD in general. I was asking if NI-USRP was playing the same role for LabView that gr-UHD plays in the GnuRadio environment.
Perhaps I should explain my application and see if you can help. I have developed some MIMO OFDM code in LabView (w/ the Modulation Toolkit and Mathscript) for USRP N210. I am trying to evaluate the performance of reconfigurable antennas in a MIMO OFDM system. The reconfigurable antennas require control signals and I would like to be able to do this from within Labview by writing/reading to/from the Debug port of the USRP board. I have done something similar in GnuRadio by making modifications to the FPGA image and using a function from gr-UHD package called "set_user_register". Would it be possible to call this function from Labview? If not, can you provide some guidance on what other methods I may be able to use to write/read to the Debug port of the USRP board?
Thanks,
Simon

Jagged wavy lines edge of CRT display with Dual Core Mac mini

My friend recently bought a Dual Core Intel Mac mini and when hooking it up to a 19 inch MAG monitor there are often wavy lines on the edges of the screen. They go up and down both sides, are jagged, and also are not static but moving quickly. Sometimes it seems to behave normally while other times if it doesn't show up on the boot screen it will show up after a little bit of use.
At first it seems that the more stuff I opened the worse it got, so I thought it could be the shared video RAM as he did not upgrade from the original 512 , but that should only slow the computer down anyway. Now I think rather than the RAM I think it could be related to the Apple DVI to VGA adapter, resloution/refresh rate, or just bad video hardware. I can't rule out that it just won't play nice with the majority of CRT monitors out there either. Sometimes changing the resolution/refresh rate helps and other time it doesn't. From what I heard my friend experienced wavy lines somewhat on his own monitor but I don't think it did it when using a DVI to HDMI cable to his Sony 50 LCD (and I didn't see it when hooking it up to mine either).
If anyone has any idea what could be going on I would greatly appreciate it. The reason it is so important is that my friend decided that the Mac mini was kind of an impulse buy and didn't need his iBook and another computer for his TV so he is going to sell it to my brother who is in need of a computer. So I don't want him to get into something that will give him problems right away.
Thanks in advance,
Robert

So is the MAG monitor your brother's monitor? That wasn't clear.
What you are seeing will most likely be limited to the MAG monitor. The MAG is experiencing some kind of noise coupling in to horizontal sync, likely from it's own power supply. You are correct that this will be related to the sync rate. Changing the vertical refresh to something higher, like 85 Hz or higher if available, might help to mask the noise. Also, power supply loading will affect how the noise manifests, so you weren't imagining when you thought that opening more applications made it worse. It didn't have anything to do with the mini but rather the different average picture level on the screen was changing the monitor's power supply loading and hence changing the beat frequency between hsync and the power supply's switching frequency.
I think it is safe to say most of what you see is bound to the monitor and not the mini. Furthermore, if you are stuck with this monitor, you can probably lessen the appearance of the noise by mucking with the refresh rate out of the mini.

DVI Signal Irregularities

When I connect my MacBook Pro to my HDTV (Sharp Aquos 37") via DVI cable, the signal looks great.
However, every 30 seconds or so, the signal gets a strange irregularity. It's hard to explain, but the displayed image seems to "split" -- with the bottom portion of the screen slightly off alignment. This "split" moves upward on the screen until it gets about half way to the top, then disappears. It's pretty frustrating to see.
Anyone know what could be the root cause? Is it my DVI cable? My laptop? My TV? Thanks in advance...
Scott
Memphis, TN

I've seen that kind of thing on CRT-based televisions but never on a digital TV. When it happens on a CRT TV, it is usually that you are seeing the beat frequency (small difference) between the 60Hz power line and the 60Hz video frame rate.
One thing you might want to try is disconnect all other video connections from the Sharp and make sure the MBP is the only thing connected. Also, make sure the MBP and the Sharp are plugged into the same wall outlet. If the irregularity goes away, it could point to a grounding problem among all your equipment. Start plugging things in one-by-one until the problem comes back. That can help you isolate the issue to a specific piece of gear or a specific connection.

Can SwitchRes X fix the lines?

I have the previous generation 15" PB, not the current one, so I can't try this myself. Since the lines people are seeing are most likely from power supply ripple noise (probably from the inverter board) coupling into the video subsystem, and since the noise is visibly manifested as a difference frequency or beat frequency between the display's scan rate and the frequency of the noise, has anyone tried using a program like SwitchRes X or DisplayConfig X to alter the pixel dot clock (suggest trying ~5% to 10% higher) to see if the beat frequency can be altered enough such that the lines disappear? Just a thought of something to try for those looking for relief outside of any Apple may eventually provide.

Upon further review of this issue, I completely retract my theory that the horizontal lines are related to power supply noise. I should have looked into this more closely before coming to that conclusion. Sorry for false hopes.

Using a microphone to measure speed

My problem is that i am trying to measure the speed of a fan using a microphone with labview, any ideas??????

And I thought this would be a tough one....
Input the microphone to your sound card, Run the fan and capture the sound. Send the sound through an FFT. If the microphone is placed near the outside of the blades, facing the output of the fan, you will get a "beat frequency" of the fan blades. This will give you a very low frequency. Divide by the number of blades and 60 and you will get the RPM of the fan.
What you are trying to do is to isolate the frequency that occurs when a fan blade passes in front of the microphone, compressing the air, pushing the cel of the mic in, then the blade passes, decompressing the air (in relative space of course), pulling the cel out. This is a very strong component of the sound you will measure with the mi
crophone, and should be very easy to see in the FFT. If you want to get fancy, you can isolate this peak in the FFT, apply the math to convert it to RPM, and output the fan speed.
Good luck. 'Sounds' like fun...

Audio Buffer error with command line app

I run a program called SBAGEN, which is a binaural beat frequency program that runs from Terminal.app - lately, when I invoke one of the scripts for this program, I get this error:
Set audio output buffer size failed, status = 1852797029
any ideas as to how to solve this?
Thanks

Resolved this issue on my own:
*SYSTEM PREF—-> SOUND —–> SOUND EFFECTS*
I needed to make sure that under +SOUND EFFECTS+, that the following was selected in the drop down menu +“Play sounds and alerts from”+: *SELECTED SOUND OUTPUT DEVICE*

Documentation for USRP 1.1 with Ettus N210

Where can I find documentation for using USRP 1.1 with the Ettus N210 device? The documentation that comes with USRP 1.1 has a tiny blurb on the N210 that points to the documentation for NI 292x devices for details. There, I find:
"For Ettus Research devices, use internal names to refer to the internal connectors inside the device case."
I'm trying to understand how to use the API to receive upon the LFRX-LF DC-50 MHz receiver daughter board. The two connectors on that board are labeled "RX-A" and "RX-B", but I can't get those names to work, nor can I get "RF1" or "RF2" to work (the names on the case).
Any suggestions?
Ultimately, I'd like to stream data from both connectors at the same time, if that's possible.

Hi ejubenville,
Support for the LFRX 0-30 MHz daughter board was just added to the NI-USRP driver in version 1.1 and documentation for this daught board is limited. While support for the LFRX is listed, I saw no mention to the LFRX-LF 0-50 MHz daughter board. I expect that your daughter board will work, but if not this may be part of the reason.
As far as the driver is concerned, the Ettus N210 and the NI-292x devices will be configured the same so there is not different documentation for the N210. I would try using RX1 and RX2 which are the names used for the other daughter boards.
Sarah Y
SDR Product Manager
National Instruments | Ettus Research

NiUSRP 1.2 / USRP N210 / beat frequencies LO

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