Hi David,
Thanks a lot for this. I will have a look on the “ATR” GPIO functionality.
Yes 40 dBm after the power amplifier inline and before the switch. I need to
check if I can find a switch with 55 dB isolation or 2 switches in cascade
summing the isolation.
Best
John
From: David Raeman <da...@synopticengineering.com>
Sent: 18 February 2025 15:41
To: john.achkar.r...@gmail.com; 'Rob Kossler' <rkoss...@nd.edu>; 'Stuart
Austin' <saus...@criticalsoftwaresystems.com>
Cc: usrp-users@lists.ettus.com
Subject: RE: [USRP-users] Re: High power TX/RX same antenna
Hi John,
You might investigate whether the “ATR” GPIO functionality built into UHD will
work for your application. It can automatically transition GPIO pins to
different states during transmission and reception.
If that doesn’t work for your use case, I’ve had success using the software
GPIO API to directly control an external T/R switch using timed commands that
were synchronized with my schedule. ATR wouldn’t work for my application
because I had TX/RX running continuously on separate channels, and I was
blanking the TX stream in software. I was allowing ~15us deadband between
timeslots for the transition, but I think it could be tightened up by measuring
and calibrating for the propagation latency and considering your switch
settling time. My code looked something like this:
usrp->set_command_time(start_tick - TX_LEADING_GUARD, m_id);
usrp->set_gpio_attr("FP0", "OUT", m_tx_assert_state, m_tx_pin_mask,
m_id);
usrp->set_command_time(end_tick + TX_TRAILING_GUARD, m_id);
usrp->set_gpio_attr("FP0", "OUT", m_tx_deassert_state, m_tx_pin_mask,
m_id);
usrp->clear_command_time(m_id);
However, I strongly suggest looking at ATR as an easier, first-choice approach.
You mention transmitting at +40dBm – is that conducted power with a power
amplifier inline, or EIRP? 55dB difference is still a lot of isolation even for
a switch.
-David
From: john.achkar.r...@gmail.com <mailto:john.achkar.r...@gmail.com>
<john.achkar.r...@gmail.com <mailto:john.achkar.r...@gmail.com> >
Sent: Tuesday, February 18, 2025 8:30 AM
To: 'Rob Kossler' <rkoss...@nd.edu <mailto:rkoss...@nd.edu> >; 'Stuart Austin'
<saus...@criticalsoftwaresystems.com
<mailto:saus...@criticalsoftwaresystems.com> >
Cc: usrp-users@lists.ettus.com <mailto:usrp-users@lists.ettus.com>
Subject: [USRP-users] Re: High power TX/RX same antenna
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Attenuators on RX port will decrease the uplink performance, which will result
lower coverage even with high power transmitted on downlink…
with active T/R switch and TDD, how shall I synchronize the DL/UL slots timing
with the switch input controller? Without any delay and very accurately.
Best,
From: Rob Kossler <rkoss...@nd.edu <mailto:rkoss...@nd.edu> >
Sent: 17 February 2025 17:38
To: Stuart Austin <saus...@criticalsoftwaresystems.com
<mailto:saus...@criticalsoftwaresystems.com> >
Cc: john.achkar.r...@gmail.com <mailto:john.achkar.r...@gmail.com> ;
usrp-users@lists.ettus.com <mailto:usrp-users@lists.ettus.com>
Subject: Re: [USRP-users] Re: High power TX/RX same antenna
If you are using TDD, you may need a T/R switch to switch out your receiver
during transmission. If you are using FDD, you may need a diplexer.
Rob
On Mon, Feb 17, 2025 at 11:20 AM Stuart Austin
<saus...@criticalsoftwaresystems.com
<mailto:saus...@criticalsoftwaresystems.com> > wrote:
Can you just add more attenuation between the output of the circulator port
that goes to the RX port on the N310?
From: john.achkar.r...@gmail.com <mailto:john.achkar.r...@gmail.com>
[mailto:john.achkar.r...@gmail.com <mailto:john.achkar.r...@gmail.com> ]
Sent: Monday, February 17, 2025 10:41 AM
To: usrp-users@lists.ettus.com <mailto:usrp-users@lists.ettus.com>
Subject: [USRP-users] High power TX/RX same antenna
Hi,
I am using a N310, with OAI to transmit 5G signal. I want to transmit 40 dBm
using one antenna connected on both TX and RX ports. The best circulator I
found has 18 dB isolation, which isn’t sufficient considering -15 dBm USRP max
input power.
What is the best approach to consider?
Thanks a lot.
Best regards,
Charbel
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