Re: [USRP-users] TDD mode with USRPs in GNU Radio

[Andy Walls via USRP-users]

Hi Johannes:

On Tue, 2019-02-26 at 11:05 +, Johannes Demel wrote:
> Hi Andy,
> 
> thanks for your answer and help. That's the pointer I was looking
> for.
> 
> Just for clarification, I' refering to this schematic:
> https://files.ettus.com/schematics/ubx/ubx.pdf
> 
> The 'SKyWorks SKY13350-385LF' switch is this SPDT component in the
> TXPA 
> block?

Yes, on Sheet 1.

It is also depicted on Sheet 11, Grid C-2, designated U32.


> I expect a configuration with separate antennas for TX and RX. But
> since 
> isolation between TX and RX chains is limited by the switch, this is
> the 
> component I need to worry about?

In my opinion, yes.

It seems kind of funny that Ettus would make a board that can blast out
20 dBm on Tx, can only tolerate -15 dBm max on Rx, and then have only a
single device that provides only 17-20 dB isolation between the Tx and
Rx.

If all the specifications from the UBX-160 page are to be believed, 
you always have to have the UBX Tx gain turned down by at least 15 dB
to not damage your UBX board.




> Otherwise I'd just separate my TX and RX antennas spatially. But
> that 
> doesn't make sense in my case since the critical component is this 
> switch in my case.

Right.

Although antenna separation needs to happen as well, so you have at
least 35 dB loss over the air.  Keep in mind that equations derived
from far field approximations don't necessarily hold in the near field.


> I aim at working in the 3.7GHz band. Thus, I assume that my receive 
> signal goes through the VMMK-3603 LNA in the RXLNA block in the 
> schematic. I wonder how that component right after the RX2 SMA works?
> I 
> assume this is a Skyworks AS236-321LF as shown on page 11 of the
> schematic.
> 
https://store.skyworksinc.com/Products/Detail/AS236321LF-Skyworks-Solutions-Inc/88944/

Take a look at the SPDT switch in Figure 1 here:
http://www.skyworksinc.com/uploads/documents/PB_RFSwitches_PB121_15B.pdf

It's not too hard to imagine what a DPDT switch looks like from there.


> Are there in fact 2 switches concatenated? Would it be appropriate
> to 
> just add up their isolation values?

Ah, yes.  As long as the USRP switches this one over to RX2, (and that
sounds like your configuration,) it looks like you get an additional
13-15 dB of isolation.  Still not enough to cover the whole 35 dB, but
you're up to a worst case minimum 30 dB isolation.

If all of the specifications are to be believed, and you know you'll
receive negligible energy on the RX2 port antenna, you only need set Tx
output gain to 5 dB of attenuation, and make sure you are using RX2 for
Rx.


> Another thought, would it be possible to configure a USRP in GR such 
> that it does continuously receive on TX/RX and then switch for the 
> duration of a transmit burst and switch back afterwards? Of course, 
> preferably this happens automagically.

I'm pretty sure this already is handled automatically by the
USRP/libuhd, but it would take a bit of searching through code to
verify.

In the case of telling the USRP you're using the TX/RX port for both Tx
and Rx, you may not get that Skyworks AS236-321LF switch switched into
the position to get the additional isolation.  You'll have to check the
code or check with Ettus.


> This thread [0] suggests that there is some kind of control. But so
> far, 
> I didn't find a definite way to tell if this covers my case with GNU 
> Radio. Also, in [1] it sounds like switching is done automagically. 

In GNURadio you should be able to set a USRP Sink to "TX/RX" and a USRP
Source to "TX/RX", and libuhd should take care of the switching
automatically, if I recall correctly.  Again, you might not get the
isolation of the second Rx switch using this configuration.


> Though, I wonder if I can just use 'UHD: USRP Sink' and 'Source' or
> if I 
> need to use the Async Sink?

I have no idea.  Never used it.

Regards,
Andy

> Cheers
> Johannes
> 
> [0] 
> 
http://lists.ettus.com/pipermail/usrp-users_lists.ettus.com/2016-October/050112.html
> [1] 
> 
https://stackoverflow.com/questions/39321262/switching-usrp-from-rx-to-tx-using-gnuradio
> 
> Am 25.02.19 um 20:30 schrieb Andy Walls:
> > 
> > > Date: Mon, 25 Feb 2019 10:29:56 +
> > > From: Johannes Demel
> > > To: "discuss-gnura...@gnu.org" 
> > > Subject: [Discuss-gnuradio] TDD mode with USRPs in GNU Radio
> > > 
> > > Hi all,
> > > 
> > > I plan to implement a TDD system with GNU Radio and X310s w
> > > UBX160s.
> > > My
> > > lab setup is as follows:
> > > - multiple USRPs (start with 2, extend to more)
> > > - each USRP shall use 1 TX and one RX port. Preferably on one
> > > daughterboard in order to extend it to MIMO later on.
> > > 
> > > At the moment the receiver runs continuously. While TX bursts
> > > happen
> > > occasionally. I'd like to turn up TX power as much as possible.
> > > But
> > > I'm
> > > concerned that this will damage the RX frontend. Especially if
> > > the
> > > RX
> > > gain is set to some high value too. Should I be concerned about
> 

Re: [USRP-users] TDD mode with USRPs in GNU Radio

[Marcus D. Leech via USRP-users]

On 02/26/2019 08:41 AM, Andy Walls via USRP-users wrote:


In my opinion, yes.

It seems kind of funny that Ettus would make a board that can blast out
20 dBm on Tx, can only tolerate -15 dBm max on Rx, and then have only a
single device that provides only 17-20 dB isolation between the Tx and
Rx.

If all the specifications from the UBX-160 page are to be believed,
you always have to have the UBX Tx gain turned down by at least 15 dB
to not damage your UBX board.


RX is protected by TWO layers of RF switch, not just one.  That gives 
you about 30-40dB of isolation.






Otherwise I'd just separate my TX and RX antennas spatially. But
that
doesn't make sense in my case since the critical component is this
switch in my case.

Right.

Although antenna separation needs to happen as well, so you have at
least 35 dB loss over the air.  Keep in mind that equations derived
from far field approximations don't necessarily hold in the near field.



I aim at working in the 3.7GHz band. Thus, I assume that my receive
signal goes through the VMMK-3603 LNA in the RXLNA block in the
schematic. I wonder how that component right after the RX2 SMA works?
I
assume this is a Skyworks AS236-321LF as shown on page 11 of the
schematic.


https://store.skyworksinc.com/Products/Detail/AS236321LF-Skyworks-Solutions-Inc/88944/

Take a look at the SPDT switch in Figure 1 here:
http://www.skyworksinc.com/uploads/documents/PB_RFSwitches_PB121_15B.pdf

It's not too hard to imagine what a DPDT switch looks like from there.



Are there in fact 2 switches concatenated? Would it be appropriate
to
just add up their isolation values?

Ah, yes.  As long as the USRP switches this one over to RX2, (and that
sounds like your configuration,) it looks like you get an additional
13-15 dB of isolation.  Still not enough to cover the whole 35 dB, but
you're up to a worst case minimum 30 dB isolation.

If all of the specifications are to be believed, and you know you'll
receive negligible energy on the RX2 port antenna, you only need set Tx
output gain to 5 dB of attenuation, and make sure you are using RX2 for
Rx.



Another thought, would it be possible to configure a USRP in GR such
that it does continuously receive on TX/RX and then switch for the
duration of a transmit burst and switch back afterwards? Of course,
preferably this happens automagically.

I'm pretty sure this already is handled automatically by the
USRP/libuhd, but it would take a bit of searching through code to
verify.

In the case of telling the USRP you're using the TX/RX port for both Tx
and Rx, you may not get that Skyworks AS236-321LF switch switched into
the position to get the additional isolation.  You'll have to check the
code or check with Ettus.



This thread [0] suggests that there is some kind of control. But so
far,
I didn't find a definite way to tell if this covers my case with GNU
Radio. Also, in [1] it sounds like switching is done automagically.

In GNURadio you should be able to set a USRP Sink to "TX/RX" and a USRP
Source to "TX/RX", and libuhd should take care of the switching
automatically, if I recall correctly.  Again, you might not get the
isolation of the second Rx switch using this configuration.



Though, I wonder if I can just use 'UHD: USRP Sink' and 'Source' or
if I
need to use the Async Sink?

I have no idea.  Never used it.

Regards,
Andy


Cheers
Johannes

[0]


http://lists.ettus.com/pipermail/usrp-users_lists.ettus.com/2016-October/050112.html

[1]


https://stackoverflow.com/questions/39321262/switching-usrp-from-rx-to-tx-using-gnuradio

Am 25.02.19 um 20:30 schrieb Andy Walls:

Date: Mon, 25 Feb 2019 10:29:56 +
From: Johannes Demel
To: "discuss-gnura...@gnu.org" 
Subject: [Discuss-gnuradio] TDD mode with USRPs in GNU Radio

Hi all,

I plan to implement a TDD system with GNU Radio and X310s w
UBX160s.
My
lab setup is as follows:
- multiple USRPs (start with 2, extend to more)
- each USRP shall use 1 TX and one RX port. Preferably on one
daughterboard in order to extend it to MIMO later on.

At the moment the receiver runs continuously. While TX bursts
happen
occasionally. I'd like to turn up TX power as much as possible.
But
I'm
concerned that this will damage the RX frontend. Especially if
the
RX
gain is set to some high value too. Should I be concerned about
that?

Yes.

https://kb.ettus.com/UBX

"TX Power (Max)

   10 MHz - 3 GHz: 20 dBm
   3 - 6 GHz: 8 - 20 dBm"

"Input Power Levels

The maximum input power for the UBX is -15 dBm."


The TX chain is isolated from the Rx chain by a SKyWorks SKY13350-
385LF
switch.
https://files.ettus.com/schematics/ubx/ubx.pdf
http://www.skyworksinc.com/Product/712/SKY13350-385LF

which claims typical isolation of 25 dB at 3 GHz on the webpage,
but
the datasheet indicates 20 dB is actually typical and 17 dB is
minimum.
UBX-160 board design, if not done right, can degrade that.

17 dB of isolation is does not cover the 35 dB difference between
max
TX power and max Rx input power.



Or
does the USRP

Re: [USRP-users] TDD mode with USRPs in GNU Radio

[Johannes Demel via USRP-users]

Hi all,

this discussion started on discuss-gnuradio in case anyone wonders.

Andy, thanks a lot for your detailed answers!

And thanks Marcus for confirming these assumptions.
So, now I only need to worry about spatial separation of my antennas.

Now, the scenario is as follows, I want my system to work in TDD mode in 
the 3.7GHz band. I want continuous reception and occasional transmit bursts.
Does UHD allow to use the TX/RX port only and do automatic switching? I 
send a burst to a USRP with a EOB flag and it does the switching 
automatically?
I could potentially use 2 antennas but a one antenna system would be 
more elegant and I hope it would prevent any accidents with high 
transmit powers and antennas that are not separated far enough.

I want to use GNU Radio and I hope I can use it as is or with minimal 
changes.

Ideally, the USRP does automatic switching and I'd either not receive 
samples during transmission on my receive chain or just the noise that 
happens to be sampled in the RX chain. I can handle echos as well. What 
I want to avoid is to implement logic that does the switching.

Cheers
Johannes


Am 26.02.19 um 15:40 schrieb Marcus D. Leech via USRP-users:
> On 02/26/2019 08:41 AM, Andy Walls via USRP-users wrote:
>>
>> In my opinion, yes.
>>
>> It seems kind of funny that Ettus would make a board that can blast out
>> 20 dBm on Tx, can only tolerate -15 dBm max on Rx, and then have only a
>> single device that provides only 17-20 dB isolation between the Tx and
>> Rx.
>>
>> If all the specifications from the UBX-160 page are to be believed,
>> you always have to have the UBX Tx gain turned down by at least 15 dB
>> to not damage your UBX board.
>>
>>
> RX is protected by TWO layers of RF switch, not just one.  That gives 
> you about 30-40dB of isolation.
> 
> 
>>
>>> Otherwise I'd just separate my TX and RX antennas spatially. But
>>> that
>>> doesn't make sense in my case since the critical component is this
>>> switch in my case.
>> Right.
>>
>> Although antenna separation needs to happen as well, so you have at
>> least 35 dB loss over the air.  Keep in mind that equations derived
>> from far field approximations don't necessarily hold in the near field.
>>
>>
>>> I aim at working in the 3.7GHz band. Thus, I assume that my receive
>>> signal goes through the VMMK-3603 LNA in the RXLNA block in the
>>> schematic. I wonder how that component right after the RX2 SMA works?
>>> I
>>> assume this is a Skyworks AS236-321LF as shown on page 11 of the
>>> schematic.
>>>
>> https://store.skyworksinc.com/Products/Detail/AS236321LF-Skyworks-Solutions-Inc/88944/
>>  
>>
>>
>> Take a look at the SPDT switch in Figure 1 here:
>> http://www.skyworksinc.com/uploads/documents/PB_RFSwitches_PB121_15B.pdf
>>
>> It's not too hard to imagine what a DPDT switch looks like from there.
>>
>>
>>> Are there in fact 2 switches concatenated? Would it be appropriate
>>> to
>>> just add up their isolation values?
>> Ah, yes.  As long as the USRP switches this one over to RX2, (and that
>> sounds like your configuration,) it looks like you get an additional
>> 13-15 dB of isolation.  Still not enough to cover the whole 35 dB, but
>> you're up to a worst case minimum 30 dB isolation.
>>
>> If all of the specifications are to be believed, and you know you'll
>> receive negligible energy on the RX2 port antenna, you only need set Tx
>> output gain to 5 dB of attenuation, and make sure you are using RX2 for
>> Rx.
>>
>>
>>> Another thought, would it be possible to configure a USRP in GR such
>>> that it does continuously receive on TX/RX and then switch for the
>>> duration of a transmit burst and switch back afterwards? Of course,
>>> preferably this happens automagically.
>> I'm pretty sure this already is handled automatically by the
>> USRP/libuhd, but it would take a bit of searching through code to
>> verify.
>>
>> In the case of telling the USRP you're using the TX/RX port for both Tx
>> and Rx, you may not get that Skyworks AS236-321LF switch switched into
>> the position to get the additional isolation.  You'll have to check the
>> code or check with Ettus.
>>
>>
>>> This thread [0] suggests that there is some kind of control. But so
>>> far,
>>> I didn't find a definite way to tell if this covers my case with GNU
>>> Radio. Also, in [1] it sounds like switching is done automagically.
>> In GNURadio you should be able to set a USRP Sink to "TX/RX" and a USRP
>> Source to "TX/RX", and libuhd should take care of the switching
>> automatically, if I recall correctly.  Again, you might not get the
>> isolation of the second Rx switch using this configuration.
>>
>>
>>> Though, I wonder if I can just use 'UHD: USRP Sink' and 'Source' or
>>> if I
>>> need to use the Async Sink?
>> I have no idea.  Never used it.
>>
>> Regards,
>> Andy
>>
>>> Cheers
>>> Johannes
>>>
>>> [0]
>>>
>> http://lists.ettus.com/pipermail/usrp-users_lists.ettus.com/2016-October/050112.html
>>  
>>
>>> [1]
>>>
>> https://stackoverflow.com/qu

Re: [USRP-users] TDD mode with USRPs in GNU Radio

[Marcus D. Leech via USRP-users]

On 02/26/2019 10:01 AM, Johannes Demel via USRP-users wrote:

Hi all,

this discussion started on discuss-gnuradio in case anyone wonders.

Andy, thanks a lot for your detailed answers!

And thanks Marcus for confirming these assumptions.
So, now I only need to worry about spatial separation of my antennas.

Now, the scenario is as follows, I want my system to work in TDD mode in
the 3.7GHz band. I want continuous reception and occasional transmit bursts.
Does UHD allow to use the TX/RX port only and do automatic switching? I
send a burst to a USRP with a EOB flag and it does the switching
automatically?
I could potentially use 2 antennas but a one antenna system would be
more elegant and I hope it would prevent any accidents with high
transmit powers and antennas that are not separated far enough.

I want to use GNU Radio and I hope I can use it as is or with minimal
changes.
UHD takes care of TX/RX sequencing in the case where both RX and TX are 
configured for the same antenna.





Ideally, the USRP does automatic switching and I'd either not receive
samples during transmission on my receive chain or just the noise that
happens to be sampled in the RX chain. I can handle echos as well. What
I want to avoid is to implement logic that does the switching.

Cheers
Johannes


Am 26.02.19 um 15:40 schrieb Marcus D. Leech via USRP-users:

On 02/26/2019 08:41 AM, Andy Walls via USRP-users wrote:

In my opinion, yes.

It seems kind of funny that Ettus would make a board that can blast out
20 dBm on Tx, can only tolerate -15 dBm max on Rx, and then have only a
single device that provides only 17-20 dB isolation between the Tx and
Rx.

If all the specifications from the UBX-160 page are to be believed,
you always have to have the UBX Tx gain turned down by at least 15 dB
to not damage your UBX board.



RX is protected by TWO layers of RF switch, not just one.  That gives
you about 30-40dB of isolation.



Otherwise I'd just separate my TX and RX antennas spatially. But
that
doesn't make sense in my case since the critical component is this
switch in my case.

Right.

Although antenna separation needs to happen as well, so you have at
least 35 dB loss over the air.  Keep in mind that equations derived
from far field approximations don't necessarily hold in the near field.



I aim at working in the 3.7GHz band. Thus, I assume that my receive
signal goes through the VMMK-3603 LNA in the RXLNA block in the
schematic. I wonder how that component right after the RX2 SMA works?
I
assume this is a Skyworks AS236-321LF as shown on page 11 of the
schematic.


https://store.skyworksinc.com/Products/Detail/AS236321LF-Skyworks-Solutions-Inc/88944/


Take a look at the SPDT switch in Figure 1 here:
http://www.skyworksinc.com/uploads/documents/PB_RFSwitches_PB121_15B.pdf

It's not too hard to imagine what a DPDT switch looks like from there.



Are there in fact 2 switches concatenated? Would it be appropriate
to
just add up their isolation values?

Ah, yes.  As long as the USRP switches this one over to RX2, (and that
sounds like your configuration,) it looks like you get an additional
13-15 dB of isolation.  Still not enough to cover the whole 35 dB, but
you're up to a worst case minimum 30 dB isolation.

If all of the specifications are to be believed, and you know you'll
receive negligible energy on the RX2 port antenna, you only need set Tx
output gain to 5 dB of attenuation, and make sure you are using RX2 for
Rx.



Another thought, would it be possible to configure a USRP in GR such
that it does continuously receive on TX/RX and then switch for the
duration of a transmit burst and switch back afterwards? Of course,
preferably this happens automagically.

I'm pretty sure this already is handled automatically by the
USRP/libuhd, but it would take a bit of searching through code to
verify.

In the case of telling the USRP you're using the TX/RX port for both Tx
and Rx, you may not get that Skyworks AS236-321LF switch switched into
the position to get the additional isolation.  You'll have to check the
code or check with Ettus.



This thread [0] suggests that there is some kind of control. But so
far,
I didn't find a definite way to tell if this covers my case with GNU
Radio. Also, in [1] it sounds like switching is done automagically.

In GNURadio you should be able to set a USRP Sink to "TX/RX" and a USRP
Source to "TX/RX", and libuhd should take care of the switching
automatically, if I recall correctly.  Again, you might not get the
isolation of the second Rx switch using this configuration.



Though, I wonder if I can just use 'UHD: USRP Sink' and 'Source' or
if I
need to use the Async Sink?

I have no idea.  Never used it.

Regards,
Andy


Cheers
Johannes

[0]


http://lists.ettus.com/pipermail/usrp-users_lists.ettus.com/2016-October/050112.html


[1]


https://stackoverflow.com/questions/39321262/switching-usrp-from-rx-to-tx-using-gnuradio


Am 25.02.19 um 20:30 schrieb Andy Walls:

Date: Mon, 25 Feb 2019 10:29:

[USRP-users] [E310] Fastlock profiles usage with UHD API

[Truan David via USRP-users]

Hi everyone!
We recently bought an E310 to try some very wide band acquisition (from 1GHz to 
5GHz) in the fastest way possible. I read about fastlock profiles and was able 
to do some early tests by adding the SPI sptr to the UHD tree and retrieving in 
the code:


uhd::spi_iface::sptr spi = 
usrp->get_device()->get_tree()->access("/mboards/0/spi").get();

I re-implemented the AD9361 fastlock functions found on the AD9361 Linux 
driver(save, recall, ...) and I think "my" fastlock API is now ready.
My idea (taken from 
http://lists.ettus.com/pipermail/usrp-users_lists.ettus.com/2016-January/017634.html)
 is to do a calibration run in which I spot the tunings taking too long, saving 
their profile using fastlock (may need more than 8 profiles). However, I am not 
sure about the usage of the fastlock recall while using UHD:
-Should I still use the "usrp->set_rx_freq" between the fastlock recall or do I 
only need to recall at the sensible freq and do nothing otherwise?
-Should I wait for the "lo_locked" sensor if I use the recall?
-And another question: does anyone ported the AD9361 to the Xlilinx-Linux used 
by the E310?

I am using UHD 3.9.2 patched with the SPI hook.

Thank you a lot for your answers!

David


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[USRP-users] Vivado license for 10 GbE

[Leandro Echevarría via USRP-users]

Hey everyone,

Upon building my own custom RFNoC images for an X310 using Vivado GUI, I'm
getting a critical warning stating the following: "Evaluation License
Warning: This design contains one or more evaluation cores that will cease
to function after a certain period of time. This design should NOT be used
in production systems". It then mentions that the "ten_gig_eth_pcs_pma" IP
core was generated using a design_linking license.

Nevertheless, I found this Xilinx's AR
 that says this error
will appear when using both BASE-R and BASE-KR cores, but that the BASE-R
one is actually free and the error message can be dismissed. I checked the
sources list and it appears that Ettus are indeed using a BASE-R IP core,
but I just wanted to make sure: can I keep generating bitstreams without
fearing the Ethernet interfaces to stop working after they run for a while?

Thanks in advance,

Leo
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Re: [USRP-users] Vivado license for 10 GbE

[Wade Fife via USRP-users]

Yes, you can ignore that error.

Thanks,

Wade

On Tue, Feb 26, 2019 at 9:56 AM Leandro Echevarría via USRP-users <
usrp-users@lists.ettus.com> wrote:

> Hey everyone,
>
> Upon building my own custom RFNoC images for an X310 using Vivado GUI, I'm
> getting a critical warning stating the following: "Evaluation License
> Warning: This design contains one or more evaluation cores that will cease
> to function after a certain period of time. This design should NOT be used
> in production systems". It then mentions that the "ten_gig_eth_pcs_pma" IP
> core was generated using a design_linking license.
>
> Nevertheless, I found this Xilinx's AR
>  that says this error
> will appear when using both BASE-R and BASE-KR cores, but that the BASE-R
> one is actually free and the error message can be dismissed. I checked the
> sources list and it appears that Ettus are indeed using a BASE-R IP core,
> but I just wanted to make sure: can I keep generating bitstreams without
> fearing the Ethernet interfaces to stop working after they run for a while?
>
> Thanks in advance,
>
> Leo
> ___
> USRP-users mailing list
> USRP-users@lists.ettus.com
> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>
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Re: [USRP-users] TDD mode with USRPs in GNU Radio

[Andy Walls via USRP-users]

Hi Marcus:

On Tue, 2019-02-26 at 12:00 -0500, usrp-users-requ...@lists.ettus.com
wrote:
> Message: 2
> Date: Tue, 26 Feb 2019 09:40:17 -0500
> From: "Marcus D. Leech"
> To: usrp-users@lists.ettus.com
> Subject: Re: [USRP-users] TDD mode with USRPs in GNU Radio
> 
> On 02/26/2019 08:41 AM, Andy Walls via USRP-users wrote:
> > 
> > In my opinion, yes.
> > 
> > It seems kind of funny that Ettus would make a board that can blast out
> > 20 dBm on Tx, can only tolerate -15 dBm max on Rx, and then have only a
> > single device that provides only 17-20 dB isolation between the Tx and
> > Rx.
> > 
> > If all the specifications from the UBX-160 page are to be believed,
> > you always have to have the UBX Tx gain turned down by at least 15 dB
> > to not damage your UBX board.
> > 
> > 
> 
> RX is protected by TWO layers of RF switch, not just one.  That gives 
> you about 30-40dB of isolation.
> 
> 
[snip]

> > Ah, yes.  As long as the USRP switches this one over to RX2, (and that
> > sounds like your configuration,) it looks like you get an additional
> > 13-15 dB of isolation.  Still not enough to cover the whole 35 dB, but
> > you're up to a worst case minimum 30 dB isolation.
> > 
> > If all of the specifications are to be believed, and you know you'll
> > receive negligible energy on the RX2 port antenna, you only need set Tx
> > output gain to 5 dB of attenuation, and make sure you are using RX2 for
> > Rx.

If one configures a USRP Sink to use the "TX/RX" port for Tx and a USRP
Source to use "TX/RX" port for Rx, does one still get both switches'
worth of isolation during Tx, or is it only the single switch's worth
of isolation in that case?

(I'm too lazy to run that down in the source code at the moment. :] )


Thanks,
Andy


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Re: [USRP-users] TDD mode with USRPs in GNU Radio

[Marcus D. Leech via USRP-users]

On 02/26/2019 12:10 PM, Andy Walls wrote:

Hi Marcus:

If one configures a USRP Sink to use the "TX/RX" port for Tx and a USRP
Source to use "TX/RX" port for Rx, does one still get both switches'
worth of isolation during Tx, or is it only the single switch's worth
of isolation in that case?

(I'm too lazy to run that down in the source code at the moment. :] )


Thanks,
Andy

You still, as far as I can tell, get two switches worth, since the RX 
channel is ALWAYS (as far as I recall) switched to the RX2 port during 
TX, which gives you

  two layers of switches regardless.



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