USRP Software Radio

cancel
Showing results for 
Search instead for 
Did you mean: 

HELP: Simple AM RX/TX?

I am new to LabVIEW and I wanted to test my USRP's and knowledge. Saddly, I am stuck even with the help of the RX and TX examples.

 

What I tried to do is create a dial tone, apply amplidtude modulation, and transmit on the TX side. For the RX side, I wanted to playback the demodulated dial tone. I beleive my TX side is correct, but I know I'm having issues with the RX.

 

  1. LabVIEW says my sound card can't playback with the settings I have and gives me an error. I created a new blank VI connecting the dial tone directly to the sound card and it plays fine (no USRP's).
  2. Looking at the recived waveform, it looks nothing like the dial tone I transmited.

Can anyone help me correct my errors?

Download All
0 Kudos
Message 1 of 19
(5,604 Views)

I am using two NIusrp 2920's if that helps

0 Kudos
Message 2 of 19
(5,430 Views)

Can anyone at least help me check to see if my AM RX/TX is correct? I can worry about the playback some other time.

0 Kudos
Message 3 of 19
(5,425 Views)

Hi Kyosake,

 

It looks like you may not have the settings configured correctly to match one another.  Make sure you're transmitting at the same Carrier Frequency that you're receiving.  That will hopefully result in better data.

Andy G
Applications Engineering
National Instruments
0 Kudos
Message 4 of 19
(5,398 Views)
Thanks for the replay.
The settings may not have been saved before i uploaded the VI's, but i still have the same issue.
0 Kudos
Message 5 of 19
(5,388 Views)

Kyosake,

 

Sorry, do you mean you set the carrier frequencies to be the same?  I also have some other recommendations--

 

1)  The IQ Sampling rate for the Tx VI should be equal to, if not higher than that of the Rx VI.

2)  The Active Antenna should be TX1 and RX2 (they must be different antennas).  This may be why the Coerced Carrier frequency looks so low, and is in fact much lower than the usable transmit range of the USRP

3)  Move the Generate Sinewave VIs outside of the while loop.

4)  Remove the Play Waveform VI from the while loop.

Andy G
Applications Engineering
National Instruments
Message 6 of 19
(5,334 Views)

I am using two different USRP's on two computers. I dont know why the settings are not saving, but I set everything to match before TX/RX. Here are screen shots of updated VI's.

 

I moved the generators and play out of the loop like you said, but I am still not getting the proper demodulated signal on the reciving side.

 

TX

AM TX2.PNG

AM TX.PNG

 

RX

AM RX2.PNG

AM RX.PNG

Download All
0 Kudos
Message 7 of 19
(5,308 Views)

I also tried moving a AM demodulate block outside of the loop, but that didnt make difference.

0 Kudos
Message 8 of 19
(5,307 Views)

Hi Kyosake,

 

Thanks for the feedback.  Have you created a service request for this by chance?  My colleague is seemingly working on the same issue, so I'm guessing you did 🙂 We'll continue moving forward on the SR for the time being.

Andy G
Applications Engineering
National Instruments
0 Kudos
Message 9 of 19
(5,277 Views)

Yes, I did create a service request but I havent heard back from anyone in three days.

0 Kudos
Message 10 of 19
(5,268 Views)