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

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.r404@gmail.com [mailto:john.achkar.r404@gmail.com]
Sent: Monday, February 17, 2025 10:41 AM
To: 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

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 rkossler@nd.edu
Sent: 17 February 2025 17:38
To: Stuart Austin SAustin@criticalsoftwaresystems.com
Cc: john.achkar.r404@gmail.com; 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 <SAustin@criticalsoftwaresystems.com mailto:SAustin@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.r404@gmail.com mailto:john.achkar.r404@gmail.com  [mailto:john.achkar.r404@gmail.com mailto:john.achkar.r404@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

USRP-users mailing list -- usrp-users@lists.ettus.com mailto:usrp-users@lists.ettus.com
To unsubscribe send an email to usrp-users-leave@lists.ettus.com mailto:usrp-users-leave@lists.ettus.com

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.r404@gmail.com john.achkar.r404@gmail.com
Sent: Tuesday, February 18, 2025 8:30 AM
To: 'Rob Kossler' rkossler@nd.edu; 'Stuart Austin' SAustin@criticalsoftwaresystems.com
Cc: usrp-users@lists.ettus.com
Subject: [USRP-users] Re: High power TX/RX same antenna

You don't often get email from john.achkar.r404@gmail.commailto:john.achkar.r404@gmail.com. Learn why this is importanthttps://aka.ms/LearnAboutSenderIdentification
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 <rkossler@nd.edumailto:rkossler@nd.edu>
Sent: 17 February 2025 17:38
To: Stuart Austin <SAustin@criticalsoftwaresystems.commailto:SAustin@criticalsoftwaresystems.com>
Cc: john.achkar.r404@gmail.commailto:john.achkar.r404@gmail.com; usrp-users@lists.ettus.commailto: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 <SAustin@criticalsoftwaresystems.commailto:SAustin@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.r404@gmail.commailto:john.achkar.r404@gmail.com [mailto:john.achkar.r404@gmail.commailto:john.achkar.r404@gmail.com]
Sent: Monday, February 17, 2025 10:41 AM
To: usrp-users@lists.ettus.commailto: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

USRP-users mailing list -- usrp-users@lists.ettus.commailto:usrp-users@lists.ettus.com
To unsubscribe send an email to usrp-users-leave@lists.ettus.commailto:usrp-users-leave@lists.ettus.com

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 david@SynopticEngineering.com
Sent: 18 February 2025 15:41
To: john.achkar.r404@gmail.com; 'Rob Kossler' rkossler@nd.edu; 'Stuart Austin' SAustin@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.r404@gmail.com mailto:john.achkar.r404@gmail.com  <john.achkar.r404@gmail.com mailto:john.achkar.r404@gmail.com >
Sent: Tuesday, February 18, 2025 8:30 AM
To: 'Rob Kossler' <rkossler@nd.edu mailto:rkossler@nd.edu >; 'Stuart Austin' <SAustin@criticalsoftwaresystems.com mailto:SAustin@criticalsoftwaresystems.com >
Cc: usrp-users@lists.ettus.com mailto:usrp-users@lists.ettus.com
Subject: [USRP-users] Re: High power TX/RX same antenna

You don't often get email from john.achkar.r404@gmail.com mailto:john.achkar.r404@gmail.com . Learn why this is important https://aka.ms/LearnAboutSenderIdentification

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 <rkossler@nd.edu mailto:rkossler@nd.edu >
Sent: 17 February 2025 17:38
To: Stuart Austin <SAustin@criticalsoftwaresystems.com mailto:SAustin@criticalsoftwaresystems.com >
Cc: john.achkar.r404@gmail.com mailto:john.achkar.r404@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 <SAustin@criticalsoftwaresystems.com mailto:SAustin@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.r404@gmail.com mailto:john.achkar.r404@gmail.com  [mailto:john.achkar.r404@gmail.com mailto:john.achkar.r404@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

USRP-users mailing list -- usrp-users@lists.ettus.com mailto:usrp-users@lists.ettus.com
To unsubscribe send an email to usrp-users-leave@lists.ettus.com mailto:usrp-users-leave@lists.ettus.com