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pulse compression matched filter

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hello every one;

My project is to use the SDR on the implementation of the pulse compression technique which is commonly used in radar systems,I already design the code using labview NXG,the idea of the code is transmitting three overlapped noisy LFM pulses which represent echoes from the three closed targets at different ranges and then applying these echoes to a matched filter which its function is to present the overlapped echoes as three targets, I already test this code on single VI on My PC without using the SDR and the result was acceptable and the targets appears at there ranges correctly as will be shown on the attached images,but when using USRP 2932 by connecting the TX1 and RX 2 through RF cable and transmit the three overlapped echoes from VI using TX1 and putting the matched filter algorithm on another VI which represent the receiver the result every many times of runs the three targets appear at different ranges and on the other runs the result was many peaks along all the chart so I want to know how to solve this problem is this problem due to the hardware or what ??!

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Solution
Accepted by topic author ASHLY19

That's going to be really hard to diagnose without any code.

 

My guess would be that there's a timing problem. What is guaranteeing that the received data is synchronized with the send data? If you just write, and then read, you'd be using Windows\OS\LabVIEW timing, and that could 10-500 ms off.

 

You'd need a mechanism (USRPs have (timed) triggers) that makes sure the start of reading of data has a fixed offset to the start sending the data.

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Thanx  

 

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I haven't got an USRP at the moment, and it's been a while...

 

I'd imagine the newer USRPs can use the FPGA, but my USRP didn't have an FPGA. I also only did a transmit (no receive). But I could upload my data, and schedule it at a certain time. I'd imagine you can schedule a receive as well, but I'm not sure.

 

Not sure what to do about the frequency shift, as I have no idea where it comes from. I'd not expect a frequency shift...

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is this mean that USRPs which use the FPGA solve the problem of the trigger so by using it I can transmit and receive  at the same time?????

and how I can schedule the receive??

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