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only Tx for a specified amount of time?

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Hi all,

 

I am having some trouble implemeing what should be a simple feature into one of the provided examples (niUSRP EX PSK Tx). I would like to have some user defined amount of Tx time and "wait" time. The issue I am having is that during my "wait" time, the Tx is displaying some bursty tranmission characteristics. Ideally, I would like the front end of the USRP to be completely quiet. I think the cause of my issues is improper use of the 'end of data?' input but as I am new to labview, I have been unable to solve this problem. Any help would be greatly appreciated!

 

Thanks,

 

Luis Gonzalez

NIST

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lugo3050,

 

Could you clarify "bursty transmission characteristics"?  Does this only occur when trying to write to file?

Wayne T. | Application Engineer | National Instruments
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In this context bursty transmission means that when my transmitter should be silent, that is not transmitting anything at all, it transmits packets of information in bursts. This problem occurs regardless of whether I am trying to write to file or not. The vi that I am having trouble with is detailed here.  

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lugo3050,

 

Looks like your boolean logic for the stop and transmit functions need further evaluation.  I would recommend highlighted execution and some probing to get a better understanding of what is happening.

Wayne T. | Application Engineer | National Instruments
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Wayne,

 

I have taken a closer look at my boolean logic and it seems to be fine. The boolean switches between true and a false at appropriate intervals defined by the user on the front panel. In the case where the boolean input to the 'end of data?' option is false, the USRP 2921 transmits as desired. The problem that I am having is that when the 'end of data?' option is true the transmitter continues to transmit, albeit only in bursts. This poses some major issues with my measurements on the Rx end. Is there some other way to induce a finite transmission? I am also trying to implement something similar with QAM; see attached code. 

 

Thanks,

 

Luis

NIST

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lugo3050,

 

The "end of data?" is just a marker or flag to indicate an end, nothing to do with starting/stopping transmission (the transmission could still be active even if transmitting nothing).  Maybe consider using your logic to control a case structure that runs the niUSRP Write Tx Data.vi when false, and nothing when true (you wouldn't need to wire anything to the end of data terminal).

Wayne T. | Application Engineer | National Instruments
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Thank you Wayne! The case structure solution seems to work well. 

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I am having this problem -- my transmit seems to bleed over into the time when a receive is taking place. If you run SwitchTXRX.vi, it shows a looping sequence of transmitting a PN sequence and then receiving. This works fine on my N210 except that I can see part of the transmitted sequence when I am in the receive state unless I set transmit to false when it switches back to the transmit state.

 

I can see less of the transmitted signal when I increase the length of time to receive a signal, which makes me think the transmitted signal continues for a little while during the receive state and then ends.

 

Any ideas how I can get my transmitted signal to terminate before receive begins, while still making this transition quickly? The fixes I have found (like "end of data") make the transmit to receive switch take a very long time.

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hello mike,

 

This thread is a year old and has been marked as solved.  Please create a new thread for your question.  You may reference this thread if you wish.

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