08-21-2015 07:46 AM
Its now been four days and still no response from the service request. Does NI not have an example for AM? It seems to me that quite a few people have NI-USRP's, has no one tried to receive a transmitted AM signal?
08-24-2015 01:58 PM
Hi Kyosake, have you heard back yet on the service request? Unfortunately we haven't been able to find a standard USRP AM example, but are experimenting with FM examples. You could potentially experiment yourself with the FM examples found at ni.com/examples to ensure that the HW is functioning properly.
08-24-2015 02:13 PM
I was told it was being worked on three days ago. . .
I have experimented with the the FM examples but I cant seem to get anything but static.
08-25-2015 01:55 PM
Hmm have you been able to use this USRP for other applications successfully in the past? Can you use the standard shipping examples to simply transmit and receive data?
08-25-2015 02:01 PM
08-26-2015 04:24 PM
Hi Kyosake,
We've been looking over some other customers' issues in the past when dealing with AM with a USRP, and it sounds like the mismatch in signals may actually be expected behavior on USRP due to a combination of LO Leakage that needs to be compensated for, and a DC offset that needs to be introduced on the receiving end. NI USRPs are based on Zero-IF Architecture. LO feed-through is expected behavior from these type of architectures. The corrections are done digitally to suppress LO feed-through.
Please test the attached VIs, which should be able to provide the necessary compensation. The receive VI includes the following modifications--
In terms of understanding generic USRP functionality, you can refer to the following link--http://www.ni.com/usrp/getting-started/
08-26-2015 10:36 PM
09-01-2015 09:31 PM
Can you help me check whether my vi is correct or not? I didn't get the desired results:the Modulation Depth(%) =0.3, the amplitude of Rx singal =0.3, when I send the Tx singal(the Modulation Depth(%) =0.3).
I didn't know whether the carrier amplitude through MT Demodulate AM VI is correct or not? Or get the carrier amplitude from other method.
Please tell me how can I modify it!
Why aren't equal in the amplitude of Tx and Rx signal????
Thank you!
09-02-2015 12:39 AM
The modified code works great, I did however have to replace the code with a MATLAB script because I couldn't run a math node. Now, I'm going to see if I can playback the received signal. I also need to look more into LO leakage and the required DC offset to fix it, as they are a new concept to me.
School just started, so I wont have a whole lot of time to experiment with the VI's, but if I have any further questions or figure out the playback I will post here.
Torry, hopefully one of the NI guys can answer your question since I am still working on understanding how AM works on the USRP's.