ST
Sivan Toledo
Sat, Jul 8, 2017 8:03 AM
Hi, I am trying to understand the input-port limit of the B2X0 series,
which is specified as -15dBm in the User's Manual (
http://files.ettus.com/manual/page_usrp_b200.html).
The issue is that if I use external front-end components (masthead LNA and
a saw filter), it is difficult to limit power to -15dBm (limiting to a 0 or
single-digit dBm is possible with common limiters).
Is the -15dBm the limit that will cause overload and distortion even on the
lowest gain setting, or is it a safely limit above which the unit may get
damanged?
Looking at the schematics of the B210, the input if fed to a switch that
can sustain almost 1W, then through something that looks like a limiter
(U800 and U813), then through another switch, and then to the inputs of the
AD9361, which can tolerate up to 2.5dBm. So it's hard to see why anything
up to 2.5dBm will damage the B2x0, and assuming that U800 and U813 do have
some useful limiting function, maybe much more is safe.
Can you please clarify? I am considering using B2x0 for an application that
may subject them to about 3dBm, maybe 3.5dBm (we use an LNA, followed by a
6dBm-max limiter, then a SAW filter with an insertion loss around 3dB), and
I want to make sure that this is safe.
Thanks, Sivan Toledo
Hi, I am trying to understand the input-port limit of the B2X0 series,
which is specified as -15dBm in the User's Manual (
http://files.ettus.com/manual/page_usrp_b200.html).
The issue is that if I use external front-end components (masthead LNA and
a saw filter), it is difficult to limit power to -15dBm (limiting to a 0 or
single-digit dBm is possible with common limiters).
Is the -15dBm the limit that will cause overload and distortion even on the
lowest gain setting, or is it a safely limit above which the unit may get
damanged?
Looking at the schematics of the B210, the input if fed to a switch that
can sustain almost 1W, then through something that looks like a limiter
(U800 and U813), then through another switch, and then to the inputs of the
AD9361, which can tolerate up to 2.5dBm. So it's hard to see why anything
up to 2.5dBm will damage the B2x0, and assuming that U800 and U813 do have
some useful limiting function, maybe much more is safe.
Can you please clarify? I am considering using B2x0 for an application that
may subject them to about 3dBm, maybe 3.5dBm (we use an LNA, followed by a
6dBm-max limiter, then a SAW filter with an insertion loss around 3dB), and
I want to make sure that this is safe.
Thanks, Sivan Toledo
DC
Dan CaJacob
Sun, Jul 9, 2017 4:11 AM
I think (having gone through this before) that the real badness happens if
you put -15 dBm in the front end and turn all the gain up to the maximum.
Then some chip in the chain goes over its limit.
Really though, with a real world system, over the air, I'd be shocked if
you could blow up the front end. What you have to be careful about is when
you cable it directly to a transmitter. Even USRP to USRP, I always use at
least 30 dB of attenuation and preferably 60 dB, just to be safe.
On Sat, Jul 8, 2017 at 4:04 AM Sivan Toledo via USRP-users <
usrp-users@lists.ettus.com> wrote:
Hi, I am trying to understand the input-port limit of the B2X0 series,
which is specified as -15dBm in the User's Manual (
http://files.ettus.com/manual/page_usrp_b200.html).
The issue is that if I use external front-end components (masthead LNA and
a saw filter), it is difficult to limit power to -15dBm (limiting to a 0 or
single-digit dBm is possible with common limiters).
Is the -15dBm the limit that will cause overload and distortion even on
the lowest gain setting, or is it a safely limit above which the unit may
get damanged?
Looking at the schematics of the B210, the input if fed to a switch that
can sustain almost 1W, then through something that looks like a limiter
(U800 and U813), then through another switch, and then to the inputs of the
AD9361, which can tolerate up to 2.5dBm. So it's hard to see why anything
up to 2.5dBm will damage the B2x0, and assuming that U800 and U813 do have
some useful limiting function, maybe much more is safe.
Can you please clarify? I am considering using B2x0 for an application
that may subject them to about 3dBm, maybe 3.5dBm (we use an LNA, followed
by a 6dBm-max limiter, then a SAW filter with an insertion loss around
3dB), and I want to make sure that this is safe.
Thanks, Sivan Toledo
USRP-users mailing list
USRP-users@lists.ettus.com
http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
--
Very Respectfully,
Dan CaJacob
I think (having gone through this before) that the real badness happens if
you put -15 dBm in the front end *and* turn all the gain up to the maximum.
Then some chip in the chain goes over its limit.
Really though, with a real world system, over the air, I'd be shocked if
you could blow up the front end. What you have to be careful about is when
you cable it directly to a transmitter. Even USRP to USRP, I always use at
least 30 dB of attenuation and preferably 60 dB, just to be safe.
On Sat, Jul 8, 2017 at 4:04 AM Sivan Toledo via USRP-users <
usrp-users@lists.ettus.com> wrote:
> Hi, I am trying to understand the input-port limit of the B2X0 series,
> which is specified as -15dBm in the User's Manual (
> http://files.ettus.com/manual/page_usrp_b200.html).
>
> The issue is that if I use external front-end components (masthead LNA and
> a saw filter), it is difficult to limit power to -15dBm (limiting to a 0 or
> single-digit dBm is possible with common limiters).
>
> Is the -15dBm the limit that will cause overload and distortion even on
> the lowest gain setting, or is it a safely limit above which the unit may
> get damanged?
>
> Looking at the schematics of the B210, the input if fed to a switch that
> can sustain almost 1W, then through something that looks like a limiter
> (U800 and U813), then through another switch, and then to the inputs of the
> AD9361, which can tolerate up to 2.5dBm. So it's hard to see why anything
> up to 2.5dBm will damage the B2x0, and assuming that U800 and U813 do have
> some useful limiting function, maybe much more is safe.
>
> Can you please clarify? I am considering using B2x0 for an application
> that may subject them to about 3dBm, maybe 3.5dBm (we use an LNA, followed
> by a 6dBm-max limiter, then a SAW filter with an insertion loss around
> 3dB), and I want to make sure that this is safe.
>
> Thanks, Sivan Toledo
>
> _______________________________________________
> USRP-users mailing list
> USRP-users@lists.ettus.com
> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>
--
Very Respectfully,
Dan CaJacob
MM
Marcus Müller
Sun, Jul 9, 2017 8:55 AM
Hi Sivan,
to add to what Dan already said: You're right, the -15 dBm limit is a
bit overzealous (though I really must stress it's better to be safe than
sorry on that side).
We're actually in the process of relaxing the limits we're stating for
this; compare [1], where we already spec a maximum input power of 0dBm.
Of course, it's absolutely correct that the maximum input power is what
we can be sure that, even under maximum gain, will not lead to damage.
Regarding U800/U813: these are ESD protection, not power limiter diodes!
Now, at +0dBm power (and even more so at +3dBm), the signal will not be
distorted only on the very lowest gain settings. Consider adding a
simple attenuator; Friis' noise formulas contradict that (having
attenuation (i.e. reducing gain) should happen as late as possible in
the signal chain to minimize overall Noise Figure), but these assume
amplifiers are still linear, and you'd probably break that condition.
If you could share the frequency bands you're working on (if preferable,
also in confidentiality directly with me), we can try to come up with a
NF-vs-gain and IIP3-vs-gain relationship that would help you choose the
optimal operating point.
Best regards,
Marcus
[1] https://kb.ettus.com/B200/B210/B200mini/B205mini#RF_Specifications
On 08.07.2017 10:03, Sivan Toledo via USRP-users wrote:
Hi, I am trying to understand the input-port limit of the B2X0 series,
which is specified as -15dBm in the User's Manual
(http://files.ettus.com/manual/page_usrp_b200.html).
The issue is that if I use external front-end components (masthead LNA
and a saw filter), it is difficult to limit power to -15dBm (limiting
to a 0 or single-digit dBm is possible with common limiters).
Is the -15dBm the limit that will cause overload and distortion even
on the lowest gain setting, or is it a safely limit above which the
unit may get damanged?
Looking at the schematics of the B210, the input if fed to a switch
that can sustain almost 1W, then through something that looks like a
limiter (U800 and U813), then through another switch, and then to the
inputs of the AD9361, which can tolerate up to 2.5dBm. So it's hard to
see why anything up to 2.5dBm will damage the B2x0, and assuming that
U800 and U813 do have some useful limiting function, maybe much more
is safe.
Can you please clarify? I am considering using B2x0 for an application
that may subject them to about 3dBm, maybe 3.5dBm (we use an LNA,
followed by a 6dBm-max limiter, then a SAW filter with an insertion
loss around 3dB), and I want to make sure that this is safe.
Thanks, Sivan Toledo
USRP-users mailing list
USRP-users@lists.ettus.com
http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
Hi Sivan,
to add to what Dan already said: You're right, the -15 dBm limit is a
bit overzealous (though I really must stress it's better to be safe than
sorry on that side).
We're actually in the process of relaxing the limits we're stating for
this; compare [1], where we already spec a maximum input power of 0dBm.
Of course, it's absolutely correct that the maximum input power is what
we can be sure that, even under maximum gain, will not lead to damage.
Regarding U800/U813: these are ESD protection, not power limiter diodes!
Now, at +0dBm power (and even more so at +3dBm), the signal will not be
distorted only on the very lowest gain settings. Consider adding a
simple attenuator; Friis' noise formulas contradict that (having
attenuation (i.e. reducing gain) should happen as late as possible in
the signal chain to minimize overall Noise Figure), but these assume
amplifiers are still linear, and you'd probably break that condition.
If you could share the frequency bands you're working on (if preferable,
also in confidentiality directly with me), we can try to come up with a
NF-vs-gain and IIP3-vs-gain relationship that would help you choose the
optimal operating point.
Best regards,
Marcus
[1] https://kb.ettus.com/B200/B210/B200mini/B205mini#RF_Specifications
On 08.07.2017 10:03, Sivan Toledo via USRP-users wrote:
> Hi, I am trying to understand the input-port limit of the B2X0 series,
> which is specified as -15dBm in the User's Manual
> (http://files.ettus.com/manual/page_usrp_b200.html).
>
> The issue is that if I use external front-end components (masthead LNA
> and a saw filter), it is difficult to limit power to -15dBm (limiting
> to a 0 or single-digit dBm is possible with common limiters).
>
> Is the -15dBm the limit that will cause overload and distortion even
> on the lowest gain setting, or is it a safely limit above which the
> unit may get damanged?
>
> Looking at the schematics of the B210, the input if fed to a switch
> that can sustain almost 1W, then through something that looks like a
> limiter (U800 and U813), then through another switch, and then to the
> inputs of the AD9361, which can tolerate up to 2.5dBm. So it's hard to
> see why anything up to 2.5dBm will damage the B2x0, and assuming that
> U800 and U813 do have some useful limiting function, maybe much more
> is safe.
>
> Can you please clarify? I am considering using B2x0 for an application
> that may subject them to about 3dBm, maybe 3.5dBm (we use an LNA,
> followed by a 6dBm-max limiter, then a SAW filter with an insertion
> loss around 3dB), and I want to make sure that this is safe.
>
> Thanks, Sivan Toledo
>
>
>
> _______________________________________________
> USRP-users mailing list
> USRP-users@lists.ettus.com
> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
ST
Sivan Toledo
Sun, Jul 9, 2017 9:37 AM
Thanks Marcus!
The 0dBm limit is much easier to work with than the -15. I indeed can add a
3 or 6dB attenuator to ensure that this is the case. Thanks a lot for the
clarification regarding U800 and U813.
I don't mind sharing the frequency band and the details of the receive
chain.
We operate at 434MHz, we use an LNA with a gain of 17dB and noise figure of
0.5dB, then a cable (up to 50m of LMR400), then a 6dBm limiter and a saw
filter with about 3dB insertion loss. I guess that an attenuator will not
have a dramatic influence on the noise figure.
To Dan and others: The LNA is a high linearity LNA which automatically
implies that it can generate a lot of power (about 1/4W); that's where my
concern comes from.
Sivan
On Sun, Jul 9, 2017 at 11:55 AM, Marcus Müller via USRP-users <
usrp-users@lists.ettus.com> wrote:
Hi Sivan,
to add to what Dan already said: You're right, the -15 dBm limit is a bit
overzealous (though I really must stress it's better to be safe than sorry
on that side).
We're actually in the process of relaxing the limits we're stating for
this; compare [1], where we already spec a maximum input power of 0dBm. Of
course, it's absolutely correct that the maximum input power is what we can
be sure that, even under maximum gain, will not lead to damage.
Regarding U800/U813: these are ESD protection, not power limiter diodes!
Now, at +0dBm power (and even more so at +3dBm), the signal will not be
distorted only on the very lowest gain settings. Consider adding a simple
attenuator; Friis' noise formulas contradict that (having attenuation (i.e.
reducing gain) should happen as late as possible in the signal chain to
minimize overall Noise Figure), but these assume amplifiers are still
linear, and you'd probably break that condition.
If you could share the frequency bands you're working on (if preferable,
also in confidentiality directly with me), we can try to come up with a
NF-vs-gain and IIP3-vs-gain relationship that would help you choose the
optimal operating point.
Best regards,
Marcus
[1] https://kb.ettus.com/B200/B210/B200mini/B205mini#RF_Specifications
On 08.07.2017 10:03, Sivan Toledo via USRP-users wrote:
Hi, I am trying to understand the input-port limit of the B2X0 series,
which is specified as -15dBm in the User's Manual (http://files.ettus.com/
manual/page_usrp_b200.html).
The issue is that if I use external front-end components (masthead LNA and
a saw filter), it is difficult to limit power to -15dBm (limiting to a 0 or
single-digit dBm is possible with common limiters).
Is the -15dBm the limit that will cause overload and distortion even on
the lowest gain setting, or is it a safely limit above which the unit may
get damanged?
Looking at the schematics of the B210, the input if fed to a switch that
can sustain almost 1W, then through something that looks like a limiter
(U800 and U813), then through another switch, and then to the inputs of the
AD9361, which can tolerate up to 2.5dBm. So it's hard to see why anything
up to 2.5dBm will damage the B2x0, and assuming that U800 and U813 do have
some useful limiting function, maybe much more is safe.
Can you please clarify? I am considering using B2x0 for an application
that may subject them to about 3dBm, maybe 3.5dBm (we use an LNA, followed
by a 6dBm-max limiter, then a SAW filter with an insertion loss around
3dB), and I want to make sure that this is safe.
Thanks, Sivan Toledo
USRP-users mailing listUSRP-users@lists.ettus.comhttp://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
USRP-users mailing list
USRP-users@lists.ettus.com
http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
Thanks Marcus!
The 0dBm limit is much easier to work with than the -15. I indeed can add a
3 or 6dB attenuator to ensure that this is the case. Thanks a lot for the
clarification regarding U800 and U813.
I don't mind sharing the frequency band and the details of the receive
chain.
We operate at 434MHz, we use an LNA with a gain of 17dB and noise figure of
0.5dB, then a cable (up to 50m of LMR400), then a 6dBm limiter and a saw
filter with about 3dB insertion loss. I guess that an attenuator will not
have a dramatic influence on the noise figure.
To Dan and others: The LNA is a high linearity LNA which automatically
implies that it can generate a lot of power (about 1/4W); that's where my
concern comes from.
Sivan
On Sun, Jul 9, 2017 at 11:55 AM, Marcus Müller via USRP-users <
usrp-users@lists.ettus.com> wrote:
> Hi Sivan,
>
> to add to what Dan already said: You're right, the -15 dBm limit is a bit
> overzealous (though I really must stress it's better to be safe than sorry
> on that side).
>
> We're actually in the process of relaxing the limits we're stating for
> this; compare [1], where we already spec a maximum input power of 0dBm. Of
> course, it's absolutely correct that the maximum input power is what we can
> be sure that, even under maximum gain, will not lead to damage.
>
> Regarding U800/U813: these are ESD protection, not power limiter diodes!
>
> Now, at +0dBm power (and even more so at +3dBm), the signal will not be
> distorted only on the very lowest gain settings. Consider adding a simple
> attenuator; Friis' noise formulas contradict that (having attenuation (i.e.
> reducing gain) should happen as late as possible in the signal chain to
> minimize overall Noise Figure), but these assume amplifiers are still
> linear, and you'd probably break that condition.
>
> If you could share the frequency bands you're working on (if preferable,
> also in confidentiality directly with me), we can try to come up with a
> NF-vs-gain and IIP3-vs-gain relationship that would help you choose the
> optimal operating point.
>
> Best regards,
>
> Marcus
>
> [1] https://kb.ettus.com/B200/B210/B200mini/B205mini#RF_Specifications
>
> On 08.07.2017 10:03, Sivan Toledo via USRP-users wrote:
>
> Hi, I am trying to understand the input-port limit of the B2X0 series,
> which is specified as -15dBm in the User's Manual (http://files.ettus.com/
> manual/page_usrp_b200.html).
>
> The issue is that if I use external front-end components (masthead LNA and
> a saw filter), it is difficult to limit power to -15dBm (limiting to a 0 or
> single-digit dBm is possible with common limiters).
>
> Is the -15dBm the limit that will cause overload and distortion even on
> the lowest gain setting, or is it a safely limit above which the unit may
> get damanged?
>
> Looking at the schematics of the B210, the input if fed to a switch that
> can sustain almost 1W, then through something that looks like a limiter
> (U800 and U813), then through another switch, and then to the inputs of the
> AD9361, which can tolerate up to 2.5dBm. So it's hard to see why anything
> up to 2.5dBm will damage the B2x0, and assuming that U800 and U813 do have
> some useful limiting function, maybe much more is safe.
>
> Can you please clarify? I am considering using B2x0 for an application
> that may subject them to about 3dBm, maybe 3.5dBm (we use an LNA, followed
> by a 6dBm-max limiter, then a SAW filter with an insertion loss around
> 3dB), and I want to make sure that this is safe.
>
> Thanks, Sivan Toledo
>
>
>
> _______________________________________________
> USRP-users mailing listUSRP-users@lists.ettus.comhttp://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>
>
>
> _______________________________________________
> USRP-users mailing list
> USRP-users@lists.ettus.com
> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>
>
MM
Marcus Müller
Sun, Jul 9, 2017 11:02 AM
Hi Sivan,
ah in that case, you'll probably be fine; NF would be (assuming all the
limiter, the filter and a potential attenuator have a 0dB Noise Figure):
$F_\text{total} = F_\text{LNA} +
\frac{F_\text{AD936x}}{G_\text{LNA}G_\text{cable}G_\text{limiter}G_\text{filter}G_\text{attenuator}}$;
The NF of the AD936x depends on the gain you use, and from rough memory
varies between let's say 35 dB @0dB gain over 25 dB @25dB, to 15 dB
@30dB to a final ca 5dB from 55dB onwards. Let's say we're in a
strong-signal case and you operate the B2xx at 30dB gain, and guessing
9dB loss at 100m distance for the cable, and assuming the limiter is
practically lossless, as well as a 6 dB attenuator
$F_\text{total} = 10^{0.05} + \frac{10^{1.5}}{10^{1.7}\cdot 10^{-0.45}
\cdot 1 \cdot 10^{-0.3} \cdot 10^{-0.6}}$;
which amounts to
$F_\text{total} = 10^{0.05} + {10^{1.5-1.7+0.45+0.3+0.6}}= 10^{0.05} +
10^{1.15}}\approx 11.5\text{ dB}$.
Now, that doesn't read very impressive, but your mentioning of SAW
filters might indicate that you're dealing with a narrowband signal,
which might mean that with the oversampling-induced SNR gain you can
effectively get a much nicer effective system temperature.
Best regards,
Marcus
On 09.07.2017 11:37, Sivan Toledo wrote:
Thanks Marcus!
The 0dBm limit is much easier to work with than the -15. I indeed can
add a 3 or 6dB attenuator to ensure that this is the case. Thanks a
lot for the clarification regarding U800 and U813.
I don't mind sharing the frequency band and the details of the receive
chain.
We operate at 434MHz, we use an LNA with a gain of 17dB and noise
figure of 0.5dB, then a cable (up to 50m of LMR400), then a 6dBm
limiter and a saw filter with about 3dB insertion loss. I guess that
an attenuator will not have a dramatic influence on the noise figure.
To Dan and others: The LNA is a high linearity LNA which automatically
implies that it can generate a lot of power (about 1/4W); that's where
my concern comes from.
Sivan
On Sun, Jul 9, 2017 at 11:55 AM, Marcus Müller via USRP-users
<usrp-users@lists.ettus.com mailto:usrp-users@lists.ettus.com> wrote:
Hi Sivan,
to add to what Dan already said: You're right, the -15 dBm limit
is a bit overzealous (though I really must stress it's better to
be safe than sorry on that side).
We're actually in the process of relaxing the limits we're stating
for this; compare [1], where we already spec a maximum input power
of 0dBm. Of course, it's absolutely correct that the maximum input
power is what we can be sure that, even under maximum gain, will
not lead to damage.
Regarding U800/U813: these are ESD protection, not power limiter
diodes!
Now, at +0dBm power (and even more so at +3dBm), the signal will
not be distorted only on the very lowest gain settings. Consider
adding a simple attenuator; Friis' noise formulas contradict that
(having attenuation (i.e. reducing gain) should happen as late as
possible in the signal chain to minimize overall Noise Figure),
but these assume amplifiers are still linear, and you'd probably
break that condition.
If you could share the frequency bands you're working on (if
preferable, also in confidentiality directly with me), we can try
to come up with a NF-vs-gain and IIP3-vs-gain relationship that
would help you choose the optimal operating point.
Best regards,
Marcus
[1]
https://kb.ettus.com/B200/B210/B200mini/B205mini#RF_Specifications
<https://kb.ettus.com/B200/B210/B200mini/B205mini#RF_Specifications>
On 08.07.2017 10:03, Sivan Toledo via USRP-users wrote:
Hi, I am trying to understand the input-port limit of the B2X0
series, which is specified as -15dBm in the User's Manual
(http://files.ettus.com/manual/page_usrp_b200.html
<http://files.ettus.com/manual/page_usrp_b200.html>).
The issue is that if I use external front-end components
(masthead LNA and a saw filter), it is difficult to limit power
to -15dBm (limiting to a 0 or single-digit dBm is possible with
common limiters).
Is the -15dBm the limit that will cause overload and distortion
even on the lowest gain setting, or is it a safely limit above
which the unit may get damanged?
Looking at the schematics of the B210, the input if fed to a
switch that can sustain almost 1W, then through something that
looks like a limiter (U800 and U813), then through another
switch, and then to the inputs of the AD9361, which can tolerate
up to 2.5dBm. So it's hard to see why anything up to 2.5dBm will
damage the B2x0, and assuming that U800 and U813 do have some
useful limiting function, maybe much more is safe.
Can you please clarify? I am considering using B2x0 for an
application that may subject them to about 3dBm, maybe 3.5dBm (we
use an LNA, followed by a 6dBm-max limiter, then a SAW filter
with an insertion loss around 3dB), and I want to make sure that
this is safe.
Thanks, Sivan Toledo
_______________________________________________
USRP-users mailing list
USRP-users@lists.ettus.com <mailto:USRP-users@lists.ettus.com>
http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
<http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com>
_______________________________________________
USRP-users mailing list
USRP-users@lists.ettus.com <mailto:USRP-users@lists.ettus.com>
http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
<http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com>
Hi Sivan,
ah in that case, you'll probably be fine; NF would be (assuming all the
limiter, the filter and a potential attenuator have a 0dB Noise Figure):
$F_\text{total} = F_\text{LNA} +
\frac{F_\text{AD936x}}{G_\text{LNA}G_\text{cable}G_\text{limiter}G_\text{filter}G_\text{attenuator}}$;
The NF of the AD936x depends on the gain you use, and from rough memory
varies between let's say 35 dB @0dB gain over 25 dB @25dB, to 15 dB
@30dB to a final ca 5dB from 55dB onwards. Let's say we're in a
strong-signal case and you operate the B2xx at 30dB gain, and guessing
9dB loss at 100m distance for the cable, and assuming the limiter is
practically lossless, as well as a 6 dB attenuator
$F_\text{total} = 10^{0.05} + \frac{10^{1.5}}{10^{1.7}\cdot 10^{-0.45}
\cdot 1 \cdot 10^{-0.3} \cdot 10^{-0.6}}$;
which amounts to
$F_\text{total} = 10^{0.05} + {10^{1.5-1.7+0.45+0.3+0.6}}= 10^{0.05} +
10^{1.15}}\approx 11.5\text{ dB}$.
Now, that doesn't read very impressive, but your mentioning of SAW
filters might indicate that you're dealing with a narrowband signal,
which might mean that with the oversampling-induced SNR gain you can
effectively get a much nicer effective system temperature.
Best regards,
Marcus
On 09.07.2017 11:37, Sivan Toledo wrote:
> Thanks Marcus!
>
> The 0dBm limit is much easier to work with than the -15. I indeed can
> add a 3 or 6dB attenuator to ensure that this is the case. Thanks a
> lot for the clarification regarding U800 and U813.
>
> I don't mind sharing the frequency band and the details of the receive
> chain.
>
> We operate at 434MHz, we use an LNA with a gain of 17dB and noise
> figure of 0.5dB, then a cable (up to 50m of LMR400), then a 6dBm
> limiter and a saw filter with about 3dB insertion loss. I guess that
> an attenuator will not have a dramatic influence on the noise figure.
>
> To Dan and others: The LNA is a high linearity LNA which automatically
> implies that it can generate a lot of power (about 1/4W); that's where
> my concern comes from.
>
> Sivan
>
>
> On Sun, Jul 9, 2017 at 11:55 AM, Marcus Müller via USRP-users
> <usrp-users@lists.ettus.com <mailto:usrp-users@lists.ettus.com>> wrote:
>
> Hi Sivan,
>
> to add to what Dan already said: You're right, the -15 dBm limit
> is a bit overzealous (though I really must stress it's better to
> be safe than sorry on that side).
>
> We're actually in the process of relaxing the limits we're stating
> for this; compare [1], where we already spec a maximum input power
> of 0dBm. Of course, it's absolutely correct that the maximum input
> power is what we can be sure that, even under maximum gain, will
> not lead to damage.
>
> Regarding U800/U813: these are ESD protection, not power limiter
> diodes!
>
> Now, at +0dBm power (and even more so at +3dBm), the signal will
> not be distorted only on the very lowest gain settings. Consider
> adding a simple attenuator; Friis' noise formulas contradict that
> (having attenuation (i.e. reducing gain) should happen as late as
> possible in the signal chain to minimize overall Noise Figure),
> but these assume amplifiers are still linear, and you'd probably
> break that condition.
>
> If you could share the frequency bands you're working on (if
> preferable, also in confidentiality directly with me), we can try
> to come up with a NF-vs-gain and IIP3-vs-gain relationship that
> would help you choose the optimal operating point.
>
> Best regards,
>
> Marcus
>
> [1]
> https://kb.ettus.com/B200/B210/B200mini/B205mini#RF_Specifications
> <https://kb.ettus.com/B200/B210/B200mini/B205mini#RF_Specifications>
>
>
> On 08.07.2017 10:03, Sivan Toledo via USRP-users wrote:
>> Hi, I am trying to understand the input-port limit of the B2X0
>> series, which is specified as -15dBm in the User's Manual
>> (http://files.ettus.com/manual/page_usrp_b200.html
>> <http://files.ettus.com/manual/page_usrp_b200.html>).
>>
>> The issue is that if I use external front-end components
>> (masthead LNA and a saw filter), it is difficult to limit power
>> to -15dBm (limiting to a 0 or single-digit dBm is possible with
>> common limiters).
>>
>> Is the -15dBm the limit that will cause overload and distortion
>> even on the lowest gain setting, or is it a safely limit above
>> which the unit may get damanged?
>>
>> Looking at the schematics of the B210, the input if fed to a
>> switch that can sustain almost 1W, then through something that
>> looks like a limiter (U800 and U813), then through another
>> switch, and then to the inputs of the AD9361, which can tolerate
>> up to 2.5dBm. So it's hard to see why anything up to 2.5dBm will
>> damage the B2x0, and assuming that U800 and U813 do have some
>> useful limiting function, maybe much more is safe.
>>
>> Can you please clarify? I am considering using B2x0 for an
>> application that may subject them to about 3dBm, maybe 3.5dBm (we
>> use an LNA, followed by a 6dBm-max limiter, then a SAW filter
>> with an insertion loss around 3dB), and I want to make sure that
>> this is safe.
>>
>> Thanks, Sivan Toledo
>>
>>
>>
>> _______________________________________________
>> USRP-users mailing list
>> USRP-users@lists.ettus.com <mailto:USRP-users@lists.ettus.com>
>> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>> <http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com>
>
>
> _______________________________________________
> USRP-users mailing list
> USRP-users@lists.ettus.com <mailto:USRP-users@lists.ettus.com>
> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
> <http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com>
>
>
DC
Dan CaJacob
Sun, Jul 9, 2017 7:46 PM
If your LNA is pumping out at 1/4W, just add an attenuator inline near your
radio to bring your signal power down to safe levels - it won't hurt you in
any appreciable way since you've got a nice LNA upfront already.
On Sun, Jul 9, 2017 at 7:03 AM Marcus Müller via USRP-users <
usrp-users@lists.ettus.com> wrote:
Hi Sivan,
ah in that case, you'll probably be fine; NF would be (assuming all the
limiter, the filter and a potential attenuator have a 0dB Noise Figure):
$F_\text{total} = F_\text{LNA} +
\frac{F_\text{AD936x}}{G_\text{LNA}G_\text{cable}G_\text{limiter}G_\text{filter}G_\text{attenuator}}$;
The NF of the AD936x depends on the gain you use, and from rough memory
varies between let's say 35 dB @0dB gain over 25 dB @25dB, to 15 dB @30dB
to a final ca 5dB from 55dB onwards. Let's say we're in a strong-signal
case and you operate the B2xx at 30dB gain, and guessing 9dB loss at 100m
distance for the cable, and assuming the limiter is practically lossless,
as well as a 6 dB attenuator
$F_\text{total} = 10^{0.05} + \frac{10^{1.5}}{10^{1.7}\cdot 10^{-0.45}
\cdot 1 \cdot 10^{-0.3} \cdot 10^{-0.6}}$;
which amounts to
$F_\text{total} = 10^{0.05} + {10^{1.5-1.7+0.45+0.3+0.6}}= 10^{0.05} +
10^{1.15}}\approx 11.5\text{ dB}$.
Now, that doesn't read very impressive, but your mentioning of SAW filters
might indicate that you're dealing with a narrowband signal, which might
mean that with the oversampling-induced SNR gain you can effectively get a
much nicer effective system temperature.
Best regards,
Marcus
On 09.07.2017 11:37, Sivan Toledo wrote:
Thanks Marcus!
The 0dBm limit is much easier to work with than the -15. I indeed can add
a 3 or 6dB attenuator to ensure that this is the case. Thanks a lot for the
clarification regarding U800 and U813.
I don't mind sharing the frequency band and the details of the receive
chain.
We operate at 434MHz, we use an LNA with a gain of 17dB and noise figure
of 0.5dB, then a cable (up to 50m of LMR400), then a 6dBm limiter and a saw
filter with about 3dB insertion loss. I guess that an attenuator will not
have a dramatic influence on the noise figure.
To Dan and others: The LNA is a high linearity LNA which automatically
implies that it can generate a lot of power (about 1/4W); that's where my
concern comes from.
Sivan
On Sun, Jul 9, 2017 at 11:55 AM, Marcus Müller via USRP-users <
usrp-users@lists.ettus.com> wrote:
Hi Sivan,
to add to what Dan already said: You're right, the -15 dBm limit is a bit
overzealous (though I really must stress it's better to be safe than sorry
on that side).
We're actually in the process of relaxing the limits we're stating for
this; compare [1], where we already spec a maximum input power of 0dBm. Of
course, it's absolutely correct that the maximum input power is what we can
be sure that, even under maximum gain, will not lead to damage.
Regarding U800/U813: these are ESD protection, not power limiter diodes!
Now, at +0dBm power (and even more so at +3dBm), the signal will not be
distorted only on the very lowest gain settings. Consider adding a simple
attenuator; Friis' noise formulas contradict that (having attenuation (i.e.
reducing gain) should happen as late as possible in the signal chain to
minimize overall Noise Figure), but these assume amplifiers are still
linear, and you'd probably break that condition.
If you could share the frequency bands you're working on (if preferable,
also in confidentiality directly with me), we can try to come up with a
NF-vs-gain and IIP3-vs-gain relationship that would help you choose the
optimal operating point.
Best regards,
Marcus
[1] https://kb.ettus.com/B200/B210/B200mini/B205mini#RF_Specifications
On 08.07.2017 10:03, Sivan Toledo via USRP-users wrote:
Hi, I am trying to understand the input-port limit of the B2X0 series,
which is specified as -15dBm in the User's Manual (
http://files.ettus.com/manual/page_usrp_b200.html).
The issue is that if I use external front-end components (masthead LNA
and a saw filter), it is difficult to limit power to -15dBm (limiting to a
0 or single-digit dBm is possible with common limiters).
Is the -15dBm the limit that will cause overload and distortion even on
the lowest gain setting, or is it a safely limit above which the unit may
get damanged?
Looking at the schematics of the B210, the input if fed to a switch that
can sustain almost 1W, then through something that looks like a limiter
(U800 and U813), then through another switch, and then to the inputs of the
AD9361, which can tolerate up to 2.5dBm. So it's hard to see why anything
up to 2.5dBm will damage the B2x0, and assuming that U800 and U813 do have
some useful limiting function, maybe much more is safe.
Can you please clarify? I am considering using B2x0 for an application
that may subject them to about 3dBm, maybe 3.5dBm (we use an LNA, followed
by a 6dBm-max limiter, then a SAW filter with an insertion loss around
3dB), and I want to make sure that this is safe.
Thanks, Sivan Toledo
USRP-users mailing listUSRP-users@lists.ettus.comhttp://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
USRP-users mailing list
USRP-users@lists.ettus.com
http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
--
Very Respectfully,
Dan CaJacob
If your LNA is pumping out at 1/4W, just add an attenuator inline near your
radio to bring your signal power down to safe levels - it won't hurt you in
any appreciable way since you've got a nice LNA upfront already.
On Sun, Jul 9, 2017 at 7:03 AM Marcus Müller via USRP-users <
usrp-users@lists.ettus.com> wrote:
> Hi Sivan,
>
> ah in that case, you'll probably be fine; NF would be (assuming all the
> limiter, the filter and a potential attenuator have a 0dB Noise Figure):
>
> $F_\text{total} = F_\text{LNA} +
> \frac{F_\text{AD936x}}{G_\text{LNA}G_\text{cable}G_\text{limiter}G_\text{filter}G_\text{attenuator}}$;
>
> The NF of the AD936x depends on the gain you use, and from rough memory
> varies between let's say 35 dB @0dB gain over 25 dB @25dB, to 15 dB @30dB
> to a final ca 5dB from 55dB onwards. Let's say we're in a strong-signal
> case and you operate the B2xx at 30dB gain, and guessing 9dB loss at 100m
> distance for the cable, and assuming the limiter is practically lossless,
> as well as a 6 dB attenuator
>
> $F_\text{total} = 10^{0.05} + \frac{10^{1.5}}{10^{1.7}\cdot 10^{-0.45}
> \cdot 1 \cdot 10^{-0.3} \cdot 10^{-0.6}}$;
>
> which amounts to
> $F_\text{total} = 10^{0.05} + {10^{1.5-1.7+0.45+0.3+0.6}}= 10^{0.05} +
> 10^{1.15}}\approx 11.5\text{ dB}$.
>
> Now, that doesn't read very impressive, but your mentioning of SAW filters
> might indicate that you're dealing with a narrowband signal, which might
> mean that with the oversampling-induced SNR gain you can effectively get a
> much nicer effective system temperature.
>
> Best regards,
> Marcus
>
>
> On 09.07.2017 11:37, Sivan Toledo wrote:
>
> Thanks Marcus!
>
> The 0dBm limit is much easier to work with than the -15. I indeed can add
> a 3 or 6dB attenuator to ensure that this is the case. Thanks a lot for the
> clarification regarding U800 and U813.
>
> I don't mind sharing the frequency band and the details of the receive
> chain.
>
> We operate at 434MHz, we use an LNA with a gain of 17dB and noise figure
> of 0.5dB, then a cable (up to 50m of LMR400), then a 6dBm limiter and a saw
> filter with about 3dB insertion loss. I guess that an attenuator will not
> have a dramatic influence on the noise figure.
>
> To Dan and others: The LNA is a high linearity LNA which automatically
> implies that it can generate a lot of power (about 1/4W); that's where my
> concern comes from.
>
> Sivan
>
>
> On Sun, Jul 9, 2017 at 11:55 AM, Marcus Müller via USRP-users <
> usrp-users@lists.ettus.com> wrote:
>
>> Hi Sivan,
>>
>> to add to what Dan already said: You're right, the -15 dBm limit is a bit
>> overzealous (though I really must stress it's better to be safe than sorry
>> on that side).
>>
>> We're actually in the process of relaxing the limits we're stating for
>> this; compare [1], where we already spec a maximum input power of 0dBm. Of
>> course, it's absolutely correct that the maximum input power is what we can
>> be sure that, even under maximum gain, will not lead to damage.
>>
>> Regarding U800/U813: these are ESD protection, not power limiter diodes!
>>
>> Now, at +0dBm power (and even more so at +3dBm), the signal will not be
>> distorted only on the very lowest gain settings. Consider adding a simple
>> attenuator; Friis' noise formulas contradict that (having attenuation (i.e.
>> reducing gain) should happen as late as possible in the signal chain to
>> minimize overall Noise Figure), but these assume amplifiers are still
>> linear, and you'd probably break that condition.
>>
>> If you could share the frequency bands you're working on (if preferable,
>> also in confidentiality directly with me), we can try to come up with a
>> NF-vs-gain and IIP3-vs-gain relationship that would help you choose the
>> optimal operating point.
>>
>> Best regards,
>>
>> Marcus
>>
>> [1] https://kb.ettus.com/B200/B210/B200mini/B205mini#RF_Specifications
>>
>> On 08.07.2017 10:03, Sivan Toledo via USRP-users wrote:
>>
>> Hi, I am trying to understand the input-port limit of the B2X0 series,
>> which is specified as -15dBm in the User's Manual (
>> http://files.ettus.com/manual/page_usrp_b200.html).
>>
>> The issue is that if I use external front-end components (masthead LNA
>> and a saw filter), it is difficult to limit power to -15dBm (limiting to a
>> 0 or single-digit dBm is possible with common limiters).
>>
>> Is the -15dBm the limit that will cause overload and distortion even on
>> the lowest gain setting, or is it a safely limit above which the unit may
>> get damanged?
>>
>> Looking at the schematics of the B210, the input if fed to a switch that
>> can sustain almost 1W, then through something that looks like a limiter
>> (U800 and U813), then through another switch, and then to the inputs of the
>> AD9361, which can tolerate up to 2.5dBm. So it's hard to see why anything
>> up to 2.5dBm will damage the B2x0, and assuming that U800 and U813 do have
>> some useful limiting function, maybe much more is safe.
>>
>> Can you please clarify? I am considering using B2x0 for an application
>> that may subject them to about 3dBm, maybe 3.5dBm (we use an LNA, followed
>> by a 6dBm-max limiter, then a SAW filter with an insertion loss around
>> 3dB), and I want to make sure that this is safe.
>>
>> Thanks, Sivan Toledo
>>
>>
>>
>> _______________________________________________
>> USRP-users mailing listUSRP-users@lists.ettus.comhttp://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>>
>>
>>
>> _______________________________________________
>> USRP-users mailing list
>> USRP-users@lists.ettus.com
>> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>>
>>
>
> _______________________________________________
> USRP-users mailing list
> USRP-users@lists.ettus.com
> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>
--
Very Respectfully,
Dan CaJacob
RA
Ralph A. Schmid, dk5ras
Wed, Jul 12, 2017 8:03 AM
About ESD protection, in my B210 the first switch U807 dies all the time; these need some protection, too :) At the moment I have removed them...
Ralph.
From: USRP-users [mailto:usrp-users-bounces@lists.ettus.com] On Behalf Of Marcus Müller via USRP-users
Sent: Sunday, July 9, 2017 10:56 AM
To: usrp-users@lists.ettus.com
Subject: Re: [USRP-users] Input power limit for B2x0 series
Hi Sivan,
to add to what Dan already said: You're right, the -15 dBm limit is a bit overzealous (though I really must stress it's better to be safe than sorry on that side).
We're actually in the process of relaxing the limits we're stating for this; compare [1], where we already spec a maximum input power of 0dBm. Of course, it's absolutely correct that the maximum input power is what we can be sure that, even under maximum gain, will not lead to damage.
Regarding U800/U813: these are ESD protection, not power limiter diodes!
Now, at +0dBm power (and even more so at +3dBm), the signal will not be distorted only on the very lowest gain settings. Consider adding a simple attenuator; Friis' noise formulas contradict that (having attenuation (i.e. reducing gain) should happen as late as possible in the signal chain to minimize overall Noise Figure), but these assume amplifiers are still linear, and you'd probably break that condition.
If you could share the frequency bands you're working on (if preferable, also in confidentiality directly with me), we can try to come up with a NF-vs-gain and IIP3-vs-gain relationship that would help you choose the optimal operating point.
Best regards,
Marcus
[1] https://kb.ettus.com/B200/B210/B200mini/B205mini#RF_Specifications
On 08.07.2017 10:03, Sivan Toledo via USRP-users wrote:
Hi, I am trying to understand the input-port limit of the B2X0 series, which is specified as -15dBm in the User's Manual (http://files.ettus.com/manual/page_usrp_b200.html).
The issue is that if I use external front-end components (masthead LNA and a saw filter), it is difficult to limit power to -15dBm (limiting to a 0 or single-digit dBm is possible with common limiters).
Is the -15dBm the limit that will cause overload and distortion even on the lowest gain setting, or is it a safely limit above which the unit may get damanged?
Looking at the schematics of the B210, the input if fed to a switch that can sustain almost 1W, then through something that looks like a limiter (U800 and U813), then through another switch, and then to the inputs of the AD9361, which can tolerate up to 2.5dBm. So it's hard to see why anything up to 2.5dBm will damage the B2x0, and assuming that U800 and U813 do have some useful limiting function, maybe much more is safe.
Can you please clarify? I am considering using B2x0 for an application that may subject them to about 3dBm, maybe 3.5dBm (we use an LNA, followed by a 6dBm-max limiter, then a SAW filter with an insertion loss around 3dB), and I want to make sure that this is safe.
Thanks, Sivan Toledo
USRP-users mailing list
USRP-users@lists.ettus.com mailto:USRP-users@lists.ettus.com
http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
About ESD protection, in my B210 the first switch U807 dies all the time; these need some protection, too :) At the moment I have removed them...
Ralph.
From: USRP-users [mailto:usrp-users-bounces@lists.ettus.com] On Behalf Of Marcus Müller via USRP-users
Sent: Sunday, July 9, 2017 10:56 AM
To: usrp-users@lists.ettus.com
Subject: Re: [USRP-users] Input power limit for B2x0 series
Hi Sivan,
to add to what Dan already said: You're right, the -15 dBm limit is a bit overzealous (though I really must stress it's better to be safe than sorry on that side).
We're actually in the process of relaxing the limits we're stating for this; compare [1], where we already spec a maximum input power of 0dBm. Of course, it's absolutely correct that the maximum input power is what we can be sure that, even under maximum gain, will not lead to damage.
Regarding U800/U813: these are ESD protection, not power limiter diodes!
Now, at +0dBm power (and even more so at +3dBm), the signal will not be distorted only on the very lowest gain settings. Consider adding a simple attenuator; Friis' noise formulas contradict that (having attenuation (i.e. reducing gain) should happen as late as possible in the signal chain to minimize overall Noise Figure), but these assume amplifiers are still linear, and you'd probably break that condition.
If you could share the frequency bands you're working on (if preferable, also in confidentiality directly with me), we can try to come up with a NF-vs-gain and IIP3-vs-gain relationship that would help you choose the optimal operating point.
Best regards,
Marcus
[1] https://kb.ettus.com/B200/B210/B200mini/B205mini#RF_Specifications
On 08.07.2017 10:03, Sivan Toledo via USRP-users wrote:
Hi, I am trying to understand the input-port limit of the B2X0 series, which is specified as -15dBm in the User's Manual (http://files.ettus.com/manual/page_usrp_b200.html).
The issue is that if I use external front-end components (masthead LNA and a saw filter), it is difficult to limit power to -15dBm (limiting to a 0 or single-digit dBm is possible with common limiters).
Is the -15dBm the limit that will cause overload and distortion even on the lowest gain setting, or is it a safely limit above which the unit may get damanged?
Looking at the schematics of the B210, the input if fed to a switch that can sustain almost 1W, then through something that looks like a limiter (U800 and U813), then through another switch, and then to the inputs of the AD9361, which can tolerate up to 2.5dBm. So it's hard to see why anything up to 2.5dBm will damage the B2x0, and assuming that U800 and U813 do have some useful limiting function, maybe much more is safe.
Can you please clarify? I am considering using B2x0 for an application that may subject them to about 3dBm, maybe 3.5dBm (we use an LNA, followed by a 6dBm-max limiter, then a SAW filter with an insertion loss around 3dB), and I want to make sure that this is safe.
Thanks, Sivan Toledo
_______________________________________________
USRP-users mailing list
USRP-users@lists.ettus.com <mailto:USRP-users@lists.ettus.com>
http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
DC
Dan CaJacob
Wed, Jul 12, 2017 11:06 AM
I agree. When a B2XX has died for me, it's always this.
On Wed, Jul 12, 2017 at 4:04 AM Ralph A. Schmid, dk5ras via USRP-users <
usrp-users@lists.ettus.com> wrote:
About ESD protection, in my B210 the first switch U807 dies all the time;
these need some protection, too :) At the moment I have removed them...
Ralph.
From: USRP-users [mailto:usrp-users-bounces@lists.ettus.com] *On Behalf
Of *Marcus Müller via USRP-users
Sent: Sunday, July 9, 2017 10:56 AM
To: usrp-users@lists.ettus.com
Subject: Re: [USRP-users] Input power limit for B2x0 series
Hi Sivan,
to add to what Dan already said: You're right, the -15 dBm limit is a bit
overzealous (though I really must stress it's better to be safe than sorry
on that side).
We're actually in the process of relaxing the limits we're stating for
this; compare [1], where we already spec a maximum input power of 0dBm. Of
course, it's absolutely correct that the maximum input power is what we can
be sure that, even under maximum gain, will not lead to damage.
Regarding U800/U813: these are ESD protection, not power limiter diodes!
Now, at +0dBm power (and even more so at +3dBm), the signal will not be
distorted only on the very lowest gain settings. Consider adding a simple
attenuator; Friis' noise formulas contradict that (having attenuation (i.e.
reducing gain) should happen as late as possible in the signal chain to
minimize overall Noise Figure), but these assume amplifiers are still
linear, and you'd probably break that condition.
If you could share the frequency bands you're working on (if preferable,
also in confidentiality directly with me), we can try to come up with a
NF-vs-gain and IIP3-vs-gain relationship that would help you choose the
optimal operating point.
Best regards,
Marcus
[1] https://kb.ettus.com/B200/B210/B200mini/B205mini#RF_Specifications
On 08.07.2017 10:03, Sivan Toledo via USRP-users wrote:
Hi, I am trying to understand the input-port limit of the B2X0 series,
which is specified as -15dBm in the User's Manual (
http://files.ettus.com/manual/page_usrp_b200.html).
The issue is that if I use external front-end components (masthead LNA and
a saw filter), it is difficult to limit power to -15dBm (limiting to a 0 or
single-digit dBm is possible with common limiters).
Is the -15dBm the limit that will cause overload and distortion even on
the lowest gain setting, or is it a safely limit above which the unit may
get damanged?
Looking at the schematics of the B210, the input if fed to a switch that
can sustain almost 1W, then through something that looks like a limiter
(U800 and U813), then through another switch, and then to the inputs of the
AD9361, which can tolerate up to 2.5dBm. So it's hard to see why anything
up to 2.5dBm will damage the B2x0, and assuming that U800 and U813 do have
some useful limiting function, maybe much more is safe.
Can you please clarify? I am considering using B2x0 for an application
that may subject them to about 3dBm, maybe 3.5dBm (we use an LNA, followed
by a 6dBm-max limiter, then a SAW filter with an insertion loss around
3dB), and I want to make sure that this is safe.
Thanks, Sivan Toledo
USRP-users mailing list
USRP-users@lists.ettus.com
http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
USRP-users mailing list
USRP-users@lists.ettus.com
http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
--
Very Respectfully,
Dan CaJacob
I agree. When a B2XX has died for me, it's always this.
On Wed, Jul 12, 2017 at 4:04 AM Ralph A. Schmid, dk5ras via USRP-users <
usrp-users@lists.ettus.com> wrote:
> About ESD protection, in my B210 the first switch U807 dies all the time;
> these need some protection, too :) At the moment I have removed them...
>
>
>
> Ralph.
>
>
>
> *From:* USRP-users [mailto:usrp-users-bounces@lists.ettus.com] *On Behalf
> Of *Marcus Müller via USRP-users
> *Sent:* Sunday, July 9, 2017 10:56 AM
> *To:* usrp-users@lists.ettus.com
> *Subject:* Re: [USRP-users] Input power limit for B2x0 series
>
>
>
> Hi Sivan,
>
> to add to what Dan already said: You're right, the -15 dBm limit is a bit
> overzealous (though I really must stress it's better to be safe than sorry
> on that side).
>
> We're actually in the process of relaxing the limits we're stating for
> this; compare [1], where we already spec a maximum input power of 0dBm. Of
> course, it's absolutely correct that the maximum input power is what we can
> be sure that, even under maximum gain, will not lead to damage.
>
> Regarding U800/U813: these are ESD protection, not power limiter diodes!
>
> Now, at +0dBm power (and even more so at +3dBm), the signal will not be
> distorted only on the very lowest gain settings. Consider adding a simple
> attenuator; Friis' noise formulas contradict that (having attenuation (i.e.
> reducing gain) should happen as late as possible in the signal chain to
> minimize overall Noise Figure), but these assume amplifiers are still
> linear, and you'd probably break that condition.
>
> If you could share the frequency bands you're working on (if preferable,
> also in confidentiality directly with me), we can try to come up with a
> NF-vs-gain and IIP3-vs-gain relationship that would help you choose the
> optimal operating point.
>
> Best regards,
>
> Marcus
>
> [1] https://kb.ettus.com/B200/B210/B200mini/B205mini#RF_Specifications
>
>
>
> On 08.07.2017 10:03, Sivan Toledo via USRP-users wrote:
>
> Hi, I am trying to understand the input-port limit of the B2X0 series,
> which is specified as -15dBm in the User's Manual (
> http://files.ettus.com/manual/page_usrp_b200.html).
>
>
>
> The issue is that if I use external front-end components (masthead LNA and
> a saw filter), it is difficult to limit power to -15dBm (limiting to a 0 or
> single-digit dBm is possible with common limiters).
>
>
>
> Is the -15dBm the limit that will cause overload and distortion even on
> the lowest gain setting, or is it a safely limit above which the unit may
> get damanged?
>
>
>
> Looking at the schematics of the B210, the input if fed to a switch that
> can sustain almost 1W, then through something that looks like a limiter
> (U800 and U813), then through another switch, and then to the inputs of the
> AD9361, which can tolerate up to 2.5dBm. So it's hard to see why anything
> up to 2.5dBm will damage the B2x0, and assuming that U800 and U813 do have
> some useful limiting function, maybe much more is safe.
>
>
>
> Can you please clarify? I am considering using B2x0 for an application
> that may subject them to about 3dBm, maybe 3.5dBm (we use an LNA, followed
> by a 6dBm-max limiter, then a SAW filter with an insertion loss around
> 3dB), and I want to make sure that this is safe.
>
>
>
> Thanks, Sivan Toledo
>
>
>
>
>
>
> _______________________________________________
>
> USRP-users mailing list
>
> USRP-users@lists.ettus.com
>
> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>
>
> _______________________________________________
> USRP-users mailing list
> USRP-users@lists.ettus.com
> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>
--
Very Respectfully,
Dan CaJacob
