Empathy List Archives

M

michalgorny01@gmail.com

Thu, Feb 27, 2025 2:01 PM

Hello,

I am working with a USRP E320. my main goal is to try to create a two-channel FMCW radar. I have noticed a significant leakage of the transmitted signal in the receive channel. the only gain level that does not cause leakage is about 20 (the allowed max is 80) while it is insufficient to register a reflection in my configuration. Is there any way to mitigate this leakage?

double gainTX = 20;

double gainRX = 20;

radio_ctrl->set_rx_gain(gainRX, radio_chanRX);

radio_ctrl->set_tx_gain(gainTX, radio_chanTX);

Hello, I am working with a USRP E320. my main goal is to try to create a two-channel FMCW radar. I have noticed a significant leakage of the transmitted signal in the receive channel. the only gain level that does not cause leakage is about 20 (the allowed max is 80) while it is insufficient to register a reflection in my configuration. Is there any way to mitigate this leakage? double gainTX = 20; double gainRX = 20; radio_ctrl->set_rx_gain(gainRX, radio_chanRX); radio_ctrl->set_tx_gain(gainTX, radio_chanTX);

RK

Rob Kossler

Thu, Feb 27, 2025 2:31 PM

If you are using timed commands and if you can verify that the tx-to-rx
synchronization is consistent every time, perhaps you could measure the
leakage signal (with attenuators connected to the RF ports) and then simply
subtract this signal from your over-the-air measurements. This method of
leakage cancellation can change over time as the device heats up so you may
need to periodically perform this calibration.
Rob

On Thu, Feb 27, 2025 at 9:02 AM michalgorny01@gmail.com wrote:

Hello,

I am working with a USRP E320. my main goal is to try to create a
two-channel FMCW radar. I have noticed a significant leakage of the
transmitted signal in the receive channel. the only gain level that does
not cause leakage is about 20 (the allowed max is 80) while it is
insufficient to register a reflection in my configuration. Is there any way
to mitigate this leakage?

double gainTX = 20;

double gainRX = 20;

radio_ctrl->set_rx_gain(gainRX, radio_chanRX);

radio_ctrl->set_tx_gain(gainTX, radio_chanTX);

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If you are using timed commands and if you can verify that the tx-to-rx synchronization is consistent every time, perhaps you could measure the leakage signal (with attenuators connected to the RF ports) and then simply subtract this signal from your over-the-air measurements. This method of leakage cancellation can change over time as the device heats up so you may need to periodically perform this calibration. Rob On Thu, Feb 27, 2025 at 9:02 AM <michalgorny01@gmail.com> wrote: > Hello, > > I am working with a USRP E320. my main goal is to try to create a > two-channel FMCW radar. I have noticed a significant leakage of the > transmitted signal in the receive channel. the only gain level that does > not cause leakage is about 20 (the allowed max is 80) while it is > insufficient to register a reflection in my configuration. Is there any way > to mitigate this leakage? > > double gainTX = 20; > > double gainRX = 20; > > radio_ctrl->set_rx_gain(gainRX, radio_chanRX); > > radio_ctrl->set_tx_gain(gainTX, radio_chanTX); > _______________________________________________ > USRP-users mailing list -- usrp-users@lists.ettus.com > To unsubscribe send an email to usrp-users-leave@lists.ettus.com >

MD

Marcus D. Leech

Thu, Feb 27, 2025 4:21 PM

On 27/02/2025 09:31, Rob Kossler via USRP-users wrote:

If you are using timed commands and if you can verify that the
tx-to-rx synchronization is consistent every time, perhaps you could
measure the leakage signal (with attenuators connected to the RF
ports) and then simply subtract this signal from your over-the-air
measurements. This method of leakage cancellation can change over
time as the device heats up so you may need to periodically perform
this calibration.
Rob

On Thu, Feb 27, 2025 at 9:02 AM michalgorny01@gmail.com wrote:

 Hello,

 I am working with a USRP E320. my main goal is to try to create a
 two-channel FMCW radar. I have noticed a significant leakage of
 the transmitted signal in the receive channel. the only gain level
 that does not cause leakage is about 20 (the allowed max is 80)
 while it is insufficient to register a reflection in my
 configuration. Is there any way to mitigate this leakage?

 double gainTX  = 20;

 double gainRX  = 20;

 radio_ctrl->set_rx_gain(gainRX, radio_chanRX);

 radio_ctrl->set_tx_gain(gainTX, radio_chanTX);

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

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It would be useful to understand the antenna plumbing in this
scenario. Both TX/RX and RX2 ports in use? A circulator? Two
antennas?

On 27/02/2025 09:31, Rob Kossler via USRP-users wrote: > If you are using timed commands and if you can verify that the > tx-to-rx synchronization is consistent every time, perhaps you could > measure the leakage signal (with attenuators connected to the RF > ports) and then simply subtract this signal from your over-the-air > measurements. This method of leakage cancellation can change over > time as the device heats up so you may need to periodically perform > this calibration. > Rob > > On Thu, Feb 27, 2025 at 9:02 AM <michalgorny01@gmail.com> wrote: > > Hello, > > I am working with a USRP E320. my main goal is to try to create a > two-channel FMCW radar. I have noticed a significant leakage of > the transmitted signal in the receive channel. the only gain level > that does not cause leakage is about 20 (the allowed max is 80) > while it is insufficient to register a reflection in my > configuration. Is there any way to mitigate this leakage? > > double gainTX = 20; > > double gainRX = 20; > > radio_ctrl->set_rx_gain(gainRX, radio_chanRX); > > radio_ctrl->set_tx_gain(gainTX, radio_chanTX); > > _______________________________________________ > USRP-users mailing list -- usrp-users@lists.ettus.com > To unsubscribe send an email to usrp-users-leave@lists.ettus.com > > > _______________________________________________ > USRP-users mailing list --usrp-users@lists.ettus.com > To unsubscribe send an email tousrp-users-leave@lists.ettus.com It would be useful to understand the antenna plumbing in this scenario. Both TX/RX and RX2 ports in use? A circulator? Two antennas?

M

michalgorny01@gmail.com

Sun, Mar 2, 2025 9:07 AM

There is one “RF A” channel, one antenna for the TX/RX port, and one antenna for the RX. I don’t need to use a circulator because I made my custom conjugate multiplication block.

MB

Martin Braun

Mon, Mar 3, 2025 2:23 PM

Are your TX and RX antennas right next to one another?

--M

On Sun, Mar 2, 2025 at 10:07 AM michalgorny01@gmail.com wrote:

There is one “RF A” channel, one antenna for the TX/RX port, and one
antenna for the RX. I don’t need to use a circulator because I made my
custom conjugate multiplication block.

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Are your TX and RX antennas right next to one another? --M On Sun, Mar 2, 2025 at 10:07 AM <michalgorny01@gmail.com> wrote: > There is one “RF A” channel, one antenna for the TX/RX port, and one > antenna for the RX. I don’t need to use a circulator because I made my > custom conjugate multiplication block. > _______________________________________________ > USRP-users mailing list -- usrp-users@lists.ettus.com > To unsubscribe send an email to usrp-users-leave@lists.ettus.com >

RK

Rob Kossler

Mon, Mar 3, 2025 2:25 PM

With an FMCW radar and a matched filter, the leakage signal will be at a
different range (close to zero range) than the targets. So, you could just
ignore this range region of your results. But, if the leakage signal is
strong enough to either saturate the A/D or to cause the corresponding
range sidelobes to interfere with target detection, then you will need to
mitigate the leakage. There will be two types of leakage: internal device
leakage (which you mentioned) but also direct antenna-to-antenna leakage.
You will likely want to deal with both of them. The method I mentioned
earlier for cancelling the leakage may help.
Rob

On Sun, Mar 2, 2025 at 4:07 AM michalgorny01@gmail.com wrote:

There is one “RF A” channel, one antenna for the TX/RX port, and one
antenna for the RX. I don’t need to use a circulator because I made my
custom conjugate multiplication block.

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

With an FMCW radar and a matched filter, the leakage signal will be at a different range (close to zero range) than the targets. So, you could just ignore this range region of your results. But, if the leakage signal is strong enough to either saturate the A/D or to cause the corresponding range sidelobes to interfere with target detection, then you will need to mitigate the leakage. There will be two types of leakage: internal device leakage (which you mentioned) but also direct antenna-to-antenna leakage. You will likely want to deal with both of them. The method I mentioned earlier for cancelling the leakage may help. Rob On Sun, Mar 2, 2025 at 4:07 AM <michalgorny01@gmail.com> wrote: > There is one “RF A” channel, one antenna for the TX/RX port, and one > antenna for the RX. I don’t need to use a circulator because I made my > custom conjugate multiplication block. > _______________________________________________ > USRP-users mailing list -- usrp-users@lists.ettus.com > To unsubscribe send an email to usrp-users-leave@lists.ettus.com >

usrp-users@lists.ettus.com

strange behavior related to gain