RE: [Discuss-gnuradio] Could this output be a problem with myHardware or the python codes?

[Paul Mathews]

Are you aware that the isolation between the transmit and receive channels of USRP daughterboards is generally < 40 dB? (This fact made it impossible for me to use the Transmit channels in my application.)  It is quite challenging to have transmit and receive channels operating simultaneously, sharing a power supply, and without much shielding. I suppose we should be surprised that the isolation is as good as it is. As others have commented, the expectation is that your transmit and receive channels will be well separated, otherwise, crosstalk can overwhelm the receiver channels.

Paul Mathews

-----Original Message-----
From: address@hidden [mailto:address@hidden On Behalf Of Bruhtesfa Ebrahim
Sent: Thursday, November 06, 2008 2:14 AM
To: Matt Ettus; address@hidden
Subject: Re: [Discuss-gnuradio] Could this output be a problem with myHardware or the python codes?

Hey,
 
 I have two XCVR2450 Trancievers.I have also two wire antennas connected to each.
So,I have separate transmit and recieve paths, but I am using a single USRP.

I am using the transmiter and reciever daughterboards at almost the same frequency.
I am transmitting at 2.45GHz and I expect to recieve a reflected signal
at a frequency of 2.45GHz + Doppler shift, so that I will detect the doppler shift.

So, what do you think is the problem?

Thanks 4 ur help !

Bruhtesfa

On Mon, Nov 3, 2008 at 5:43 PM, Matt Ettus <address@hidden> wrote:

Are you trying to simultaneously transmit and receive with the XCVR2450?  Because it doesn't do that -- it does not do FDD.  The RFX-series will work in full duplex mode, but you still need to put them on different frequencies.

If you really need to do this with the XCVR2450, then you will need two of them.

Matt

Bruhtesfa Ebrahim wrote:

Hey all,
  May be my question could be out of topic as it is can be a hardware problem, so excuses.
  The Thing is....I am using USRP with XCVR2450 Tranciever to develop a doppler radar(in duplex mode).
 So, I was checking out my devices.
 When I use USRP_fft.py just to see the environment signals without enabling my USRP_siggen.py, I see a certain signal level.
Then when i start to transmit and recieve in duplex mode running  these two python codes simultaneously in different shell scripts; the signal(FFT) level
I am recieving decreases too much. Normally, I should get a more strong recieved signal rather since I am transmitting.
 So, does anyone has experience in this stuff ? If so, what do you think is the problem? could it be a problem with my Trancievers.
 Thank you!
  Bruhtesfa

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