how to get S21 from usrp 2901 using labview 2014

[Tawahaa38]

In thesis they are using VNA for S21. 

Please help me in making a transmitter that can transmit a p&n sequence or you can say a digital signal. And also help me to make receiver that can after receiving reflected signal effectively take correlation of the transmitted signal and reflected signal. 

I have attach my previous transmitter and receiver codes in which I was sending a sine wave but as you said, sine wave is not giving a good result of the correlation that can help me differentiating signal reflected from a body or a metal.

Thanks for your time and help
I will immensely appreciate your quick response.

[Tawahaa38]

Please also let me know how to convert a string to a numeric value.

I have attach the P&N sequence transmitter and reciver that I have made but there are some errors if you could help me remive them or advice ma a better way

Thankzz

[Hey.itsDale]

Could you provide a link to the thesis?

If they are taking an IFFT of S21, I think it is safe to assume that they are taking that measurement over a range of frequencies. The 2901 could perhaps give you an approximation of S21 at one frequency at a time, but as I have said before, this is not the intended use for the device. Also, you would need to physically alter your setup as I described in my first post to get the reading anyways. Therefore, it seems to me that the 2901 will not work for this application and you willl need a VNA instead.

Please see these functions for string/number conversions:

http://zone.ni.com/reference/en-XX/help/371361L-01/glang/string_numb_conver_func/

[Tawahaa38]

thanks for your time. well i had change my approach from the that thesis and trying something different so please if you could help me with that I will immensely appreciate.

Please help me in making a transmitter that can transmit a p&n sequence or you can say a digital signal. And also help me to make receiver that can after receiving reflected signal effectively take correlation of the transmitted signal and reflected signal. 

I have attach my previous transmitter and receiver codes in which I was sending a sine wave but as you said, sine wave is not giving a good result of the correlation that can help me differentiating signal reflected from a body or a metal.

Here are the attach files I am working on

[Shalini.M]

Hi Tawahaa38,

Are you getting an error or not seeing the expected data/results? Could you be more specific on what the question is? 

[Tawahaa38]

Hi Shalini 

forget about the previous code please let me know that can we use usrp 2901 as full duplex for transmitting and receiving of signal at same frequency. Like transmitting from TX/RX of RF0 and receiving at RX2 of RF1. I am using horn anteena and carrier freq of 2.1GHz.
Please help me with this as this is my new task.
Also let me know that if we can use a coupler to find S21 with 2901 either in full duplex or by using two usrp 2901.

Thankss

[Shalini.M]

Hi Tawahaa38, 

You can use the USRP 2901 as full duplex for transmitting if you use the different channels (like you described, RF0 to transmit and RF1 to receive). 

If you haven't already seen it, the spec sheet and getting started guide are good resources to check for capabilities of your device. 

Regarding your second question, even with a coupler I would not recommend using a USRP to measure s-parameters because the device itself is not calibrated. 

[Tawahaa38]

Thanks for your reply I have seen the spec sheet and I know it can be used as full duplex.
But my question was can we use it as full duplex at same freq by using two given RF's ports as these ports are quite close to each other so I was thinking that if a high power signal comes at RX it might damage the internal circuitry?? 

Regards

[Shalini.M]

As long as you are not exceeding the Maximum input power I don't see any concern with damaging the internal circuitry. You can use an attenuator to avoid that as well.