Hi, I would like to use an X310 with UBX in a monostatic antenna configuration (same frequency range). This is for example common in RFID readers.
My transmit power is 30dBm (ZHL-25W-272+ after the USRP), fed into a 6dBi antenna. Now if I use a circulator, I find isolation of around 15dB (e.g. https://www.everythingrf.com/products/rf-microwave-circulators/mesa-microwave/769-185-mmccc700a). This means my RX input sees 15dBm. Stupidly, the UBX datasheet wants a maximum input signal of -15dBm. So it's 30dB too strong! Alternatively, I could use a directional coupler. However, the directivity is typically around 20dB (e.g. https://www.everythingrf.com/products/directional-couplers/rf-lambda/45-89-rfdc8m3g10d) which brings me to +10dBm at the RX input. If I assume directivity is not an issue, the signal at RX is limited by the S11 of the antenna (typically 15dB). With 10dB of coupling: 30dBm-15dB-10dB=5dBm. Still too high and a incurs a 10dB noise figure penalty. As another option, I could add 30dB attenuator after the circulator. But this results in an unacceptable 30dB noise figure penalty. Do I understand anything wrong or is a monostatic TRX just not possible with USRP? Lukas PS1: I am well aware that this self-interference is a major challenge. However, in my case the trouble does not even come from the fact that I have self interference but that the RX frontend does not want a signal larger than -15dBm. This is different, for example in RFID readers. PS2: I found a bunch of projects describing an RFID reader based on USRP. The issue of power levels was always conveniently ignored (likely low output powers were used or a bi-static configuration altogether). _______________________________________________ USRP-users mailing list USRP-users@lists.ettus.com http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
