S
soring@ayecka.com
Sun, Mar 26, 2023 5:37 AM
I am working with Ettus B205 mini i. We operate it on Ubuntu + C++.
I have a few problems.
A. It seems the DC cancellation mechanism is quite aggressive. It creates a notch at DC. I can overcome it by using lo_offset parameter, but as I am trying to sample at the lowest symbol rate possible, it’s probably not a very good option.
B.There is very high LO leakage - even when the signal is at high power.
To demonstrate I use the Ettus command tx_waveforms with a waveform set to SINE at 1MHz.
Rate is 5.76e6
Gain is 50 db
freq is 1e9.
You can see the LO is -10dbc and also image at -40 dbc. Both are much too high.
Any suggestions please?
Thank you,
Sorin
I am working with Ettus B205 mini i. We operate it on Ubuntu + C++.\
I have a few problems.
A. It seems the DC cancellation mechanism is quite aggressive. It creates a notch at DC. I can overcome it by using lo_offset parameter, but as I am trying to sample at the lowest symbol rate possible, it’s probably not a very good option.
B.There is very high LO leakage - even when the signal is at high power. \
To demonstrate I use the Ettus command tx_waveforms with a waveform set to SINE at 1MHz.\
Rate is 5.76e6\
Gain is 50 db\
freq is 1e9.\
You can see the LO is -10dbc and also image at -40 dbc. Both are much too high.\
\
Any suggestions please?\
\
Thank you,
Sorin
MD
Marcus D. Leech
Sun, Mar 26, 2023 9:13 PM
I am working with Ettus B205 mini i. We operate it on Ubuntu + C++.
I have a few problems.
A. It seems the DC cancellation mechanism is quite aggressive. It
creates a notch at DC. I can overcome it by using lo_offset parameter,
but as I am trying to sample at the lowest symbol rate possible, it’s
probably not a very good option.
YOu can always just move the LO to the edge of your passband, where
there'll be roll-off anyway. Not sure I understand this
comment. The LO_OFFSET can be configured in the HARDWARE, so it
will be nearly-transparent to the rest of your processing.
B.There is very high LO leakage - even when the signal is at high power.
To demonstrate I use the Ettus command tx_waveforms with a waveform
set to SINE at 1MHz.
Rate is 5.76e6
Gain is 50 db
freq is 1e9.
You can see the LO is -10dbc and also image at -40 dbc. Both are much
too high.
A gain of 50dB on the B205 is about 32dB below the maximum RF gain.
Try two things:
Lower the baseband amplitude a bit when using tx_waveforms--perhaps 0.85
Crank the RF gain up a bit, that should improve the
carrier-to-LO-leakage ratio.
But, also, consider LO offset in the TX path as well.
The image performance may well improve with a not-saturated baseband.
On 26/03/2023 01:37, soring@ayecka.com wrote:
>
> I am working with Ettus B205 mini i. We operate it on Ubuntu + C++.
> I have a few problems.
>
> A. It seems the DC cancellation mechanism is quite aggressive. It
> creates a notch at DC. I can overcome it by using lo_offset parameter,
> but as I am trying to sample at the lowest symbol rate possible, it’s
> probably not a very good option.
>
YOu can always just move the LO to the edge of your passband, where
there'll be roll-off anyway. Not sure I understand this
comment. The LO_OFFSET can be configured in the HARDWARE, so it
will be nearly-transparent to the rest of your processing.
> B.There is very high LO leakage - even when the signal is at high power.
> To demonstrate I use the Ettus command tx_waveforms with a waveform
> set to SINE at 1MHz.
> Rate is 5.76e6
> Gain is 50 db
> freq is 1e9.
> You can see the LO is -10dbc and also image at -40 dbc. Both are much
> too high.
>
A gain of 50dB on the B205 is about 32dB below the maximum RF gain.
Try two things:
Lower the baseband amplitude a bit when using tx_waveforms--perhaps 0.85
Crank the RF gain up a bit, that should improve the
carrier-to-LO-leakage ratio.
But, also, consider LO offset in the TX path as well.
The image performance may well improve with a not-saturated baseband.
>
> Any suggestions please?
>
> Thank you,
>
> Sorin
>
>
>
> _______________________________________________
> USRP-users mailing list -- usrp-users@lists.ettus.com
> To unsubscribe send an email to usrp-users-leave@lists.ettus.com
S
soring@ayecka.com
Mon, Mar 27, 2023 2:13 AM
Thank you.
A. Let me understand. Can I make the lo_offset higher than sampling rate/2 ?
B. I will try. About “But, also, consider LO offset in the TX path as well.” I don’t want to use a tunable filter.
We did work with other Analog devices component. They are capable of better performance than they show in your device.
Thank you.
A. Let me understand. Can I make the lo_offset higher than sampling rate/2 ?
B. I will try. About “But, also, consider LO offset in the TX path as well.” I don’t want to use a tunable filter. \
\
We did work with other Analog devices component. They are capable of better performance than they show in your device.
S
soring@ayecka.com
Mon, Mar 27, 2023 10:33 AM
I am generating modulated signal. I am varying the digital signal amplitude. In order to observe the image I use the lo-offset. I get a low image rejection. Analog devices people told me that this shows the chip is not calibrated properly.
I am generating modulated signal. I am varying the digital signal amplitude. In order to observe the image I use the lo-offset. I get a low image rejection. Analog devices people told me that this shows the chip is not calibrated properly.
RK
Rob Kossler
Tue, Mar 28, 2023 2:06 PM
Hi Sorin,
Regarding the maximum LO offset you can use:
LO-offset-max = (master_clock_rate - sample_rate) / 2;
This equation ensures that your desired bandwidth (determined by sample
rate), will fit within the digital stream (at rate MCR) that is supplied to
the FPGA from the RF front end. So, with the B200 series, you need to set
the master_clock_rate accordingly.
Rob
On Tue, Mar 28, 2023 at 9:54 AM soring@ayecka.com wrote:
Thank you.
A. Let me understand. Can I make the lo_offset higher than sampling rate/2
?
B. I will try. About “But, also, consider LO offset in the TX path as
well.” I don’t want to use a tunable filter.
We did work with other Analog devices component. They are capable of
better performance than they show in your device.
USRP-users mailing list -- usrp-users@lists.ettus.com
To unsubscribe send an email to usrp-users-leave@lists.ettus.com
Hi Sorin,
Regarding the maximum LO offset you can use:
LO-offset-max = (master_clock_rate - sample_rate) / 2;
This equation ensures that your desired bandwidth (determined by sample
rate), will fit within the digital stream (at rate MCR) that is supplied to
the FPGA from the RF front end. So, with the B200 series, you need to set
the master_clock_rate accordingly.
Rob
On Tue, Mar 28, 2023 at 9:54 AM <soring@ayecka.com> wrote:
> Thank you.
>
> A. Let me understand. Can I make the lo_offset higher than sampling rate/2
> ?
>
> B. I will try. About “But, also, consider LO offset in the TX path as
> well.” I don’t want to use a tunable filter.
>
> We did work with other Analog devices component. They are capable of
> better performance than they show in your device.
>
>
> _______________________________________________
> 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
Tue, Mar 28, 2023 2:27 PM
On 28/03/2023 10:06, Rob Kossler via USRP-users wrote:
Hi Sorin,
Regarding the maximum LO offset you can use:
LO-offset-max = (master_clock_rate - sample_rate) / 2;
This equation ensures that your desired bandwidth (determined by
sample rate), will fit within the digital stream (at rate MCR) that
is supplied to the FPGA from the RF front end. So, with the B200
series, you need to set the master_clock_rate accordingly.
Rob
IN addition, on the B2xx, you need to set the analog bandwidth high
enough to accommodate that setting.
On Tue, Mar 28, 2023 at 9:54 AM soring@ayecka.com wrote:
Thank you.
A. Let me understand. Can I make the lo_offset higher than
sampling rate/2 ?
B. I will try. About “But, also, consider LO offset in the TX path
as well.” I don’t want to use a tunable filter.
We did work with other Analog devices component. They are capable
of better performance than they show in your device.
_______________________________________________
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
On 28/03/2023 10:06, Rob Kossler via USRP-users wrote:
> Hi Sorin,
> Regarding the maximum LO offset you can use:
> LO-offset-max = (master_clock_rate - sample_rate) / 2;
> This equation ensures that your desired bandwidth (determined by
> sample rate), will fit within the digital stream (at rate MCR) that
> is supplied to the FPGA from the RF front end. So, with the B200
> series, you need to set the master_clock_rate accordingly.
> Rob
IN addition, on the B2xx, you need to set the analog bandwidth high
enough to accommodate that setting.
>
> On Tue, Mar 28, 2023 at 9:54 AM <soring@ayecka.com> wrote:
>
> Thank you.
>
> A. Let me understand. Can I make the lo_offset higher than
> sampling rate/2 ?
>
> B. I will try. About “But, also, consider LO offset in the TX path
> as well.” I don’t want to use a tunable filter.
>
> We did work with other Analog devices component. They are capable
> of better performance than they show in your device.
>
>
> _______________________________________________
> 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
MD
Marcus D. Leech
Tue, Mar 28, 2023 2:35 PM
I am generating modulated signal. I am varying the digital signal
amplitude. In order to observe the image I use the lo-offset. I get a
low image rejection. Analog devices people told me that this shows the
chip is not calibrated properly.
What version of UHD are you using?
I can tell you that the drivers for B2xx use a lot of code provided by
ADI to do things like calibration and setup.
On 27/03/2023 06:33, soring@ayecka.com wrote:
>
> I am generating modulated signal. I am varying the digital signal
> amplitude. In order to observe the image I use the lo-offset. I get a
> low image rejection. Analog devices people told me that this shows the
> chip is not calibrated properly.
>
>
What version of UHD are you using?
I can tell you that the drivers for B2xx use a lot of code provided by
ADI to do things like calibration and setup.
MD
Marcus D. Leech
Tue, Mar 28, 2023 10:02 PM
I am generating modulated signal. I am varying the digital signal
amplitude. In order to observe the image I use the lo-offset. I get a
low image rejection. Analog devices people told me that this shows the
chip is not calibrated properly.
USRP-users mailing list -- usrp-users@lists.ettus.com
To unsubscribe send an email to usrp-users-leave@lists.ettus.com
I think we're going to need more details of your setup, including
exactly how you're generating your baseband signals.
ADI claims better than about -50dBc for images, and I did some crude
tests, as did another user with a lab
spec-an, and the device is acting more-or-less according to spec.
On 27/03/2023 06:33, soring@ayecka.com wrote:
>
> I am generating modulated signal. I am varying the digital signal
> amplitude. In order to observe the image I use the lo-offset. I get a
> low image rejection. Analog devices people told me that this shows the
> chip is not calibrated properly.
>
>
> _______________________________________________
> USRP-users mailing list -- usrp-users@lists.ettus.com
> To unsubscribe send an email to usrp-users-leave@lists.ettus.com
I think we're going to need more details of your setup, including
exactly how you're generating your baseband signals.
ADI claims better than about -50dBc for images, and I did some crude
tests, as did another user with a lab
spec-an, and the device is acting more-or-less according to spec.
RE
Ron Economos
Tue, Mar 28, 2023 10:53 PM
Here's an example from a B210. This is a DVB-S2 signal at 10 Msps,
master clock at 40 MHz, lo offset of 4 MHz, and gain set to 70. Remember
that the actual average power of the digital signal is RBW/bandwidth.
30,000/6,000,000 = 0.005. 10*log10(0.005) = -23 dB. So the average power
is 23 dB greater.
B210 spectrum
Ron
On 3/28/23 15:02, Marcus D. Leech wrote:
I am generating modulated signal. I am varying the digital signal
amplitude. In order to observe the image I use the lo-offset. I get a
low image rejection. Analog devices people told me that this shows
the chip is not calibrated properly.
USRP-users mailing list -- usrp-users@lists.ettus.com
To unsubscribe send an email to usrp-users-leave@lists.ettus.com
I think we're going to need more details of your setup, including
exactly how you're generating your baseband signals.
ADI claims better than about -50dBc for images, and I did some crude
tests, as did another user with a lab
spec-an, and the device is acting more-or-less according to spec.
USRP-users mailing list -- usrp-users@lists.ettus.com
To unsubscribe send an email to usrp-users-leave@lists.ettus.com
Here's an example from a B210. This is a DVB-S2 signal at 10 Msps,
master clock at 40 MHz, lo offset of 4 MHz, and gain set to 70. Remember
that the actual average power of the digital signal is RBW/bandwidth.
30,000/6,000,000 = 0.005. 10*log10(0.005) = -23 dB. So the average power
is 23 dB greater.
B210 spectrum
Ron
On 3/28/23 15:02, Marcus D. Leech wrote:
> On 27/03/2023 06:33, soring@ayecka.com wrote:
>>
>> I am generating modulated signal. I am varying the digital signal
>> amplitude. In order to observe the image I use the lo-offset. I get a
>> low image rejection. Analog devices people told me that this shows
>> the chip is not calibrated properly.
>>
>>
>> _______________________________________________
>> USRP-users mailing list -- usrp-users@lists.ettus.com
>> To unsubscribe send an email to usrp-users-leave@lists.ettus.com
> I think we're going to need more details of your setup, including
> exactly how you're generating your baseband signals.
>
> ADI claims better than about -50dBc for images, and I did some crude
> tests, as did another user with a lab
> spec-an, and the device is acting more-or-less according to spec.
>
> _______________________________________________
> USRP-users mailing list -- usrp-users@lists.ettus.com
> To unsubscribe send an email to usrp-users-leave@lists.ettus.com
S
soring@ayecka.com
Wed, Mar 29, 2023 4:55 AM
Thank you!
