USRP problems in recieving ANY HELP WOULD BE REALLY APPRECIATED

[Eldokch]

Hello All,

I am having a problem that i think is in the software of the usrp which is

I want to transmit the signal below but strangely enough i recieve a one with spikes and reversed as well

i have been on this problem for weeks now and i can't figure a solution

So please i would really appreciate your help as i am stuck for the moment

The modulationg waveform is the one i want to transmit

as you notice the time axis is diffrent i am sending with a rate diffrent than the recieving one.HOW IS THAT POSSIBLE ?

but here the recievied wave is similar to the transmitted...but when i run the program again i get this

now the rate is diffrent and also the wave recieved itself

and here's the VI

[rcaimano]

Hi Eldokch,

What device are you using?

One thing I would try first is to open the examples folder from the Start Menu by navigating to Start»All Programs»National Instruments»NI-USRP»Examples»LabVIEW 20xx (32bit).

Once the Example folder opens, open both niUSRP Tx Continuous Async.vi and niUSRP Rx Continuous Async.vi and begin by making sure that the IP addresses of both VIs are pointed to the same NI USRP device and running the Tx VI followed by the Rx VI.

Do you get the same behavior when you run both VIs?

[Eldokch]

I am Using the 2920 .

I have done this already but still the same thing.

if you can try to for youself and see what i mean i would be really grateful

the thing is i am stuck in this part for weeks..and this shouldn't even be a problem

i am just trying to send a signal over a certian frequency..why i recieved it reversed and filled with spikes...i will never know

sorry for complaining and the informal way of writing .

[rcaimano]

This seems to be a problem because you are generating a completely real signal without any imaginary portion to it. We tried it on our end here and had the same result. 

What if you were to generate a complex signal like in the niUSRP EX Tx Continuous Async (CDB Cluster) example? Here they generate both a real and a complex portion of the signal.

[ErikL]

The USRP Is a direct conversion transmitter and receiver. I and Q are needed to create an RF signal. Elimination of one or the other essentially creates an AM signal. So you are transmitting an AM signal. However, to other phenomenon affect you on RX. The first is that your received signal will have a time delay and this shows up as a phase rotation. So, it will be split between I and Q with the complex magnitude being your received AM signal. The second is that there is a DC filter in the receiver that could filter AM signals that stay high or low for too long. Third is that frequency offset will put slow rolling sine waves into your RX'd AM modulated signal.
Bottom line for now, use the complex magnitude of I and Q and you will be much closer to the result you are looking for.

[Eldokch]

First thanks for your reply

i understood what you said,but still how can i make the signal real and imaginary but still it's the same exact signal i am trying to send here in my example ?