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View all threadsTWINRX Gain
The TwinRx daughtercard identifies as having 0-93dB gain range. Is this true? If I dial in 90dB am I truly getting 90dB of gain and my incoming signal is amplified that much or is there some sort of offset and the gain range is something different? I believe the UBX-160 offers 0-31.5dB.
Thanks
Mark
It’s the gain control range. Not the absolute gain. I don’t know of the top of my head how much of that range is gain and how much is attenuation.
Sent from my iPhone
On Sep 29, 2020, at 1:43 PM, Mark Koenig via USRP-users usrp-users@lists.ettus.com wrote:
The TwinRx daughtercard identifies as having 0-93dB gain range. Is this true? If I dial in 90dB am I truly getting 90dB of gain and my incoming signal is amplified that much or is there some sort of offset and the gain range is something different? I believe the UBX-160 offers 0-31.5dB.
Thanks
Mark
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Marcus,
Thank you for the quick response. In my application I am trying to remove the true gain I am applying to the signal. So when you refer to control range, moving from 0 to 10, may result in only 5dB of gain, or something to that effect, correct? When you have that information of the true gain applied, can you pass it along?
Thank you very much.
Mark
From: Marcus D Leech patchvonbraun@gmail.com
Sent: Tuesday, September 29, 2020 1:51 PM
To: Mark Koenig mark.koenig@iubelttechnologies.com
Cc: usrp-users@lists.ettus.com USRP-users@lists.ettus.com
Subject: Re: [USRP-users] TWINRX Gain
It’s the gain control range. Not the absolute gain. I don’t know of the top of my head how much of that range is gain and how much is attenuation.
Sent from my iPhone
On Sep 29, 2020, at 1:43 PM, Mark Koenig via USRP-users usrp-users@lists.ettus.com wrote:
The TwinRx daughtercard identifies as having 0-93dB gain range. Is this true? If I dial in 90dB am I truly getting 90dB of gain and my incoming signal is amplified that much or is there some sort of offset and the gain range is something different? I believe the UBX-160 offers 0-31.5dB.
Thanks
Mark
USRP-users mailing list
USRP-users@lists.ettus.com
http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
On 09/29/2020 01:54 PM, Mark Koenig wrote:
Marcus,
Thank you for the quick response. In my application I am trying to
remove the true gain I am applying to the signal. So when you refer
to control range, moving from 0 to 10, may result in only 5dB of gain,
or something to that effect, correct? When you have that information
of the true gain applied, can you pass it along?
Thank you very much.
Mark
If you're trying to mathematically remove the gain to estimate actual
power at the antenna, you aren't doing it right.
You need to use a known calibration source, and build a calibration
table over your expected operating parameters.
The fact is that actual delivered gain will change with center frequency
and temperature (although the temperature effects will
be small).
Yes, I understand gain varies with temperature and frequency, I just wasnt sure if there was any receive chain analysis performed with the daughtecard to give the developer an idea of what type of gain is provided over the attenuation range at various frequencies. I am not too concerned about tenths of dBs....I was just interested in what the actual gain range provided by the card is.
Thanks
Mark
From: Marcus D. Leech patchvonbraun@gmail.com
Sent: Tuesday, September 29, 2020 1:58 PM
To: Mark Koenig mark.koenig@iubelttechnologies.com
Cc: usrp-users@lists.ettus.com usrp-users@lists.ettus.com
Subject: Re: [USRP-users] TWINRX Gain
On 09/29/2020 01:54 PM, Mark Koenig wrote:
Marcus,
Thank you for the quick response. In my application I am trying to remove the true gain I am applying to the signal. So when you refer to control range, moving from 0 to 10, may result in only 5dB of gain, or something to that effect, correct? When you have that information of the true gain applied, can you pass it along?
Thank you very much.
Mark
If you're trying to mathematically remove the gain to estimate actual power at the antenna, you aren't doing it right.
You need to use a known calibration source, and build a calibration table over your expected operating parameters.
The fact is that actual delivered gain will change with center frequency and temperature (although the temperature effects will
be small).
On 09/29/2020 02:02 PM, Mark Koenig wrote:
Yes, I understand gain varies with temperature and frequency, I just
wasnt sure if there was any receive chain analysis performed with the
daughtecard to give the developer an idea of what type of gain is
provided over the attenuation range at various frequencies. I am not
too concerned about tenths of dBs....I was just interested in what the
actual gain range provided by the card is.
Thanks
Mark
If you look at the first page of this:
https://files.ettus.com/schematics/twinrx/TwinRX%20RF%20Board%20Rev%20D.pdf
You can see the overall block diagram. You can also see several PE43503
attenuators, sprinkled among several different MMIC amplifiers, and
various different RF pathways through switches and filters depending
on band. It would be hard for me to unwind all of that and give you
a definitive answer.
Even for the IF processing, there are two different IFs, depending on
the frequency band--again with various distributions of gain and
attenuation (either explicit attenuation, or attenuation via
filtering)--all of which have considerable uncertainty--due to
batch-to-batch
variability and temperature effects. I'm fairly sure that even the
designer of the board couldn't tell you, for any given board configuration
what the actual gain measured between the antenna input an the ADC
input actually was, with better than 5dB confidence. Which is where
calibration comes in.
https://files.ettus.com/schematics/twinrx/TwinRX%20IF%20Board%20Rev%20C.pdf
In a laboratory instrument, like a spectrum analyser, all of this is
painstakingly calibrated at the factory, usually using lookup tables (or the
analog-era equivalent), based on well-characterized calibration
sources. So when you set the gain level on the front-panel of the device
to some dB value, you'll actually get that value at the measurement
point and when you look at the measurement on the display and it
says -70dBm, it's actually -70dBm at the input terminal. SDRs aren't
that, typically. Although one could build a fairly nice lab instrument
around an SDR, using all the aforementioned calibration exercises, etc.
Now, this all, I admit, sounds a tad "lecturey". I know you probably
know all of this, but many on the list don't, or perhaps haven't thought
about
it much. So, I'm prompted to deliver this, or a very similar
"lecture" a few times a year due to similar queries to yours.
I get it, thanks for the block diagrams. I will look into doing a lab test with a calibrated source.
From: Marcus D. Leech patchvonbraun@gmail.com
Sent: Tuesday, September 29, 2020 2:23 PM
To: Mark Koenig mark.koenig@iubelttechnologies.com
Cc: usrp-users@lists.ettus.com usrp-users@lists.ettus.com
Subject: Re: [USRP-users] TWINRX Gain
On 09/29/2020 02:02 PM, Mark Koenig wrote:
Yes, I understand gain varies with temperature and frequency, I just wasnt sure if there was any receive chain analysis performed with the daughtecard to give the developer an idea of what type of gain is provided over the attenuation range at various frequencies. I am not too concerned about tenths of dBs....I was just interested in what the actual gain range provided by the card is.
Thanks
Mark
If you look at the first page of this:
https://files.ettus.com/schematics/twinrx/TwinRX%20RF%20Board%20Rev%20D.pdf
You can see the overall block diagram. You can also see several PE43503 attenuators, sprinkled among several different MMIC amplifiers, and
various different RF pathways through switches and filters depending on band. It would be hard for me to unwind all of that and give you
a definitive answer.
Even for the IF processing, there are two different IFs, depending on the frequency band--again with various distributions of gain and
attenuation (either explicit attenuation, or attenuation via filtering)--all of which have considerable uncertainty--due to batch-to-batch
variability and temperature effects. I'm fairly sure that even the designer of the board couldn't tell you, for any given board configuration
what the actual gain measured between the antenna input an the ADC input actually was, with better than 5dB confidence. Which is where
calibration comes in.
https://files.ettus.com/schematics/twinrx/TwinRX%20IF%20Board%20Rev%20C.pdf
In a laboratory instrument, like a spectrum analyser, all of this is painstakingly calibrated at the factory, usually using lookup tables (or the
analog-era equivalent), based on well-characterized calibration sources. So when you set the gain level on the front-panel of the device
to some dB value, you'll actually get that value at the measurement point and when you look at the measurement on the display and it
says -70dBm, it's actually -70dBm at the input terminal. SDRs aren't that, typically. Although one could build a fairly nice lab instrument
around an SDR, using all the aforementioned calibration exercises, etc.
Now, this all, I admit, sounds a tad "lecturey". I know you probably know all of this, but many on the list don't, or perhaps haven't thought about
it much. So, I'm prompted to deliver this, or a very similar "lecture" a few times a year due to similar queries to yours.
Just an FYI, all of our USRPs define 0 dB gain as the smallest overall gain
that is supported, and then it goes up. TwinRX has a wide input range of
amplitudes, so much of that 90 dB is from attenuators that enable you to
nicely see the +10 dBm input signals. So gain range != amplification, it's
the combo of all gain-varying components.
--M
On Tue, Sep 29, 2020 at 8:30 PM Mark Koenig via USRP-users <
usrp-users@lists.ettus.com> wrote:
I get it, thanks for the block diagrams. I will look into doing a lab
test with a calibrated source.
From: Marcus D. Leech patchvonbraun@gmail.com
Sent: Tuesday, September 29, 2020 2:23 PM
To: Mark Koenig mark.koenig@iubelttechnologies.com
Cc: usrp-users@lists.ettus.com usrp-users@lists.ettus.com
Subject: Re: [USRP-users] TWINRX Gain
On 09/29/2020 02:02 PM, Mark Koenig wrote:
Yes, I understand gain varies with temperature and frequency, I just wasnt
sure if there was any receive chain analysis performed with the daughtecard
to give the developer an idea of what type of gain is provided over the
attenuation range at various frequencies. I am not too concerned about
tenths of dBs....I was just interested in what the actual gain range
provided by the card is.
Thanks
Mark
If you look at the first page of this:
https://files.ettus.com/schematics/twinrx/TwinRX%20RF%20Board%20Rev%20D.pdf
You can see the overall block diagram. You can also see several PE43503
attenuators, sprinkled among several different MMIC amplifiers, and
various different RF pathways through switches and filters depending on
band. It would be hard for me to unwind all of that and give you
a definitive answer.
Even for the IF processing, there are two different IFs, depending on the
frequency band--again with various distributions of gain and
attenuation (either explicit attenuation, or attenuation via
filtering)--all of which have considerable uncertainty--due to
batch-to-batch
variability and temperature effects. I'm fairly sure that even the
designer of the board couldn't tell you, for any given board configuration
what the actual gain measured between the antenna input an the ADC input
actually was, with better than 5dB confidence. Which is where
calibration comes in.
https://files.ettus.com/schematics/twinrx/TwinRX%20IF%20Board%20Rev%20C.pdf
In a laboratory instrument, like a spectrum analyser, all of this is
painstakingly calibrated at the factory, usually using lookup tables (or the
analog-era equivalent), based on well-characterized calibration
sources. So when you set the gain level on the front-panel of the device
to some dB value, you'll actually get that value at the measurement
point and when you look at the measurement on the display and it
says -70dBm, it's actually -70dBm at the input terminal. SDRs aren't
that, typically. Although one could build a fairly nice lab instrument
around an SDR, using all the aforementioned calibration exercises, etc.
Now, this all, I admit, sounds a tad "lecturey". I know you probably know
all of this, but many on the list don't, or perhaps haven't thought about
it much. So, I'm prompted to deliver this, or a very similar "lecture"
a few times a year due to similar queries to yours.
USRP-users mailing list
USRP-users@lists.ettus.com
http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com