Hey Paul, Ya! you are correct, the isolation is a problem.But what is curious is when i operate the transmitter and reciever simultaneously,the signal level of the reciver decreases too much(cancels out) . If some of the signal from the transmitter antenna is also recived by the reciver antenna, I think the signal recived should increase in amplitude, because the frequency of the signals sent and recived are almost the same(except the small doppler shift). But, what occurs is the opposite.
Bruhtesfa On Thu, Nov 6, 2008 at 4:14 PM, Paul Mathews <[EMAIL PROTECTED]> wrote: > 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:* [EMAIL PROTECTED] [mailto: > discuss-gnuradio-bounces+opto <discuss-gnuradio-bounces%2Bopto>= > [EMAIL PROTECTED] *On Behalf Of *Bruhtesfa Ebrahim > *Sent:* Thursday, November 06, 2008 2:14 AM > *To:* Matt Ettus; discuss-gnuradio@gnu.org > *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 <[EMAIL PROTECTED]> 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 >>> ------------------------------------------------------------------------ >>> >>> _______________________________________________ >>> Discuss-gnuradio mailing list >>> Discuss-gnuradio@gnu.org >>> http://lists.gnu.org/mailman/listinfo/discuss-gnuradio >>> >>> >> >> >
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