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Today's Topics:
1. nirio_quirks.h:39: bad for loop ? (David Binderman)
2. Question about LO Locked (Wallace, Frank L CIV NSWCDD, Q41)
3. Re: Question about LO Locked (Martin Braun)
4. Daughter board with a log response ([email protected])
5. Re: Question about LO Locked (Ian Buckley)
6. Re: Daughter board with a log response (Marcus D. Leech)
7. Re: Full-duplex MIMO issues with B210 board (Ian Buckley)
8. Timed transmission after U/L errors (Dario Fertonani)
9. Re: Daughter board with a log response (Venkatesh Sandilya)
10. Re: Daughter board with a log response (Marcus D. Leech)
11. Re: Daughter board with a log response (Ian Buckley)
12. Re: [Openbts-discuss] new uhd breaks uplink? (Tom Tsou)
13. Re: Daughter board with a log response (Venkatesh Sandilya)
----------------------------------------------------------------------
Message: 1
Date: Fri, 10 Apr 2015 06:26:58 +0000
From: David Binderman <[email protected]>
To: "[email protected]" <[email protected]>
Subject: [USRP-users] nirio_quirks.h:39: bad for loop ?
Message-ID: <[email protected]>
Content-Type: text/plain; charset="iso-8859-1"
Hello there,
uhd-release_003_008_002/host/include/uhd/transport/nirio/nirio_quirks.h:39:38:
warning: sizeof on array function parameter will return size of 'const uint32_t
*' (aka 'const unsigned int *') instead of 'const uint32_t []'
[-Wsizeof-array-argument]
for (size_t i = 0; i <
sizeof(tx_stream_indices)/sizeof(*tx_stream_indices); i++) {
Regards
David Binderman
------------------------------
Message: 2
Date: Fri, 10 Apr 2015 16:26:54 +0000
From: "Wallace, Frank L CIV NSWCDD, Q41" <[email protected]>
To: "[email protected]" <[email protected]>
Subject: [USRP-users] Question about LO Locked
Message-ID:
<cb21b46a39458b43b8b6c8ddf8431fd2231de...@naeanrfkxm09v.nadsusea.nads.navy.mil>
Content-Type: text/plain; charset="us-ascii"
I have two N210 radios connected with the MIMO cable. On the master radio, I
told it to use an external reference source. I have the slave using the MIMO
reference.
This worked well until one day I forgot to turn on the 10 MHz external
reference and didn't notice. The "Ref Locked" sensor still reported true even
though there was no signal on the input. What is the "Ref Locked" supposed to
tell me. I thought it would tell me when it doesn't have an external reference.
Thanks,
Frank
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Message: 3
Date: Fri, 10 Apr 2015 09:30:35 -0700
From: Martin Braun <[email protected]>
To: [email protected]
Subject: Re: [USRP-users] Question about LO Locked
Message-ID: <[email protected]>
Content-Type: text/plain; charset=windows-1252; format=flowed
On 10.04.2015 09:26, Wallace, Frank L CIV NSWCDD, Q41 via USRP-users wrote:
> I have two N210 radios connected with the MIMO cable. On the master
> radio, I told it to use an external reference source. I have the
> slave using the MIMO reference. This worked well until one day I
> forgot to turn on the 10 MHz external reference and didn't notice.
> The "Ref Locked" sensor still reported true even though there was no
> signal on the input. What is the "Ref Locked" supposed to tell me.
> I thought it would tell me when it doesn't have an external
> reference.
That is true only if you tell the device to actually use an external
reference. Then, this sensor can be used to tell you if the external 10
MHz is working (but more importantly, that the PLL for the reference
clock is locked).
Cheers,
M
------------------------------
Message: 4
Date: Fri, 10 Apr 2015 12:33:44 -0400
From: [email protected]
To: [email protected]
Subject: [USRP-users] Daughter board with a log response
Message-ID: <[email protected]>
Content-Type: text/plain; charset="us-ascii"
Hello
We are using a USRP N200 that has a DBSR2X daughter board. We are
decoding signals at 1090 MHz that have a very large dynamic range Our old
system used receivers that had log amps with a dynamic range of over 80 db and
are linear when you plot input power vs output amplitude.
We plotted the output of the DBSR2X using a signal generator as an input
source. We then plotted the input power vs output amplitude and it is very
non linear. Do you have a daughter board with a log characteristic or could
you suggest another way.
Thank you.
Regards,
John Keller
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Message: 5
Date: Fri, 10 Apr 2015 10:09:29 -0700
From: Ian Buckley <[email protected]>
To: "Wallace, Frank L CIV NSWCDD, Q41" <[email protected]>
Cc: "[email protected]" <[email protected]>
Subject: Re: [USRP-users] Question about LO Locked
Message-ID: <[email protected]>
Content-Type: text/plain; charset=us-ascii
Frank,
The way N2x0 works is that it has an internal 10MHz TCXO which is used as the
default 10MHz reference w.r.t the downstream PLL/100MHz VCXO. When you connect
an external 10MHz reference (or an internal GPSDO, or a MIMO cable) this
replaces the internal 10MHz as the source of the reference. As Martin indicates
the LOCK indication comes from the PLL that all possible reference sources
drive.
-Ian
On Apr 10, 2015, at 9:26 AM, "Wallace, Frank L CIV NSWCDD, Q41 via USRP-users"
<[email protected]> wrote:
> I have two N210 radios connected with the MIMO cable. On the master radio,
> I told it to use an external reference source. I have the slave using the
> MIMO reference.
> This worked well until one day I forgot to turn on the 10 MHz external
> reference and didn't notice. The "Ref Locked" sensor still reported true
> even though there was no signal on the input. What is the "Ref Locked"
> supposed to tell me. I thought it would tell me when it doesn't have an
> external reference.
>
> Thanks,
> Frank
>
> _______________________________________________
> USRP-users mailing list
> [email protected]
> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
------------------------------
Message: 6
Date: Fri, 10 Apr 2015 13:12:10 -0400
From: "Marcus D. Leech" <[email protected]>
To: [email protected]
Subject: Re: [USRP-users] Daughter board with a log response
Message-ID: <[email protected]>
Content-Type: text/plain; charset="iso-8859-1"; Format="flowed"
On 04/10/2015 12:33 PM, John Keller via USRP-users wrote:
> Hello
> We are using a USRP N200 that has a DBSR2X daughter board. We are
> decoding signals at 1090 MHz that have a very large dynamic range Our
> old system used receivers that had log amps with a dynamic range of
> over 80 db and are linear when you plot input power vs output amplitude.
> We plotted the output of the DBSR2X using a signal generator as an
> input source. We then plotted the input power vs output amplitude and
> it is very non linear. Do you have a daughter board with a log
> characteristic or could you suggest another way.
> Thank you.
> Regards,
> John Keller
>
>
> _______________________________________________
> USRP-users mailing list
> [email protected]
> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
How are you plotting this?
The power of a signal is proportional to the square of the voltage. The
DBSRX2 receiver should be very linear, except at the very upper end,
perhaps.
Logarithmic amplifier chains are generally *ONLY* used in
high-dynamic-range power detection, they aren't general-purpose RF
subsystems.
The DBSRX2 on an N200 should have more than 80dB of dynamic range,
depending on sample rates, and bandwidth settings of the DBSRX2 card.
The instantaneous power of a signal can be calculated using:
P = (I*I)+(Q*Q)
Square-root and average to taste.
So, what is it that you're actually measuring and plotting? The DBSRX2
should be quite linear over a fairly large dynamic range.
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Message: 7
Date: Fri, 10 Apr 2015 11:00:18 -0700
From: Ian Buckley <[email protected]>
To: Tom Tsou <[email protected]>
Cc: "[email protected]" <[email protected]>
Subject: Re: [USRP-users] Full-duplex MIMO issues with B210 board
Message-ID: <[email protected]>
Content-Type: text/plain; charset=windows-1252
The 30.72MHz issue is now resolved in UHD @ HEAD of both maint and master.
If anyone see's any further issues @30.72MHz with 2x2 operation please let us
know.
-Ian
On Mar 19, 2015, at 1:29 PM, Tom Tsou <[email protected]> wrote:
> On Thu, Mar 19, 2015 at 1:52 AM, Ian Buckley via USRP-users
> <[email protected]> wrote:
>> Marcus,
>> You've been given bad information by R&D?RX and TX H/W paths are
>> orthogonal?2x2 MIMO@ 30.72MHz is a legal configuration. (It is however the
>> maximum legal sample rate for this configuration)
>
> Confirming the following B210 items:
>
> * 2x2 MIMO at 30.72 MHz is a valid configuration.
> * Full-duplex or Rx/Tx only does not restrict the clock rate setting.
> * Operation with 2x2 MIMO at 30.72 MHz may generate bit-level errors.
>
> Ettus R&D has reproduced and diagnosed the clocking issue and a fix is
> in progress. In the meantime with 2x2 MIMO, master clock rates that
> approach the maximum allowable value of 30.72 MHz should be avoided.
> Single channel operation is not affected.
>
> For 2x2 LTE purposes, clocking at 7.68 or 15.36 MHz provides coverage
> up to 15 MHz channels. 20 MHz LTE can be covered with 23.04 MHz clock
> and sample rates.
>
> -TT
------------------------------
Message: 8
Date: Fri, 10 Apr 2015 20:18:31 +0200
From: Dario Fertonani <[email protected]>
To: "[email protected]" <[email protected]>
Subject: [USRP-users] Timed transmission after U/L errors
Message-ID:
<cajgedahqcmy0xo9pb9+qwomrisahxzhdrvmcr2xp0de2wws...@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
We are seeing a weird behavior that hints at a problem in recovering from
U/L transmit errors. I wonder if we are using the timed send API and
tx_metadata_t properly.
We call send within a loop, so that every time the transmission is timed
and that the interval between two consecutive transmissions is equal to the
desired chunk duration. Essentially, all is done with
txMetaData.time_spec += ChunkDuration_s;
with the loop.
All goes well until an error U/L occurs. Soon after that, a few chunks
later (1-3 ms), the transmit stream appears to be misaligned. Still nice
and strong, but not aligned with the original timing.
All we want is that, after a packet doesn't get transmitted properly (U/L
errors), the stream can go on as if nothing happened. Any special care that
should be taken to achieve this behavior?
Thanks,
Dario
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Message: 9
Date: Fri, 10 Apr 2015 16:17:47 -0400
From: Venkatesh Sandilya <[email protected]>
To: "Marcus D. Leech" <[email protected]>, "[email protected]"
<[email protected]>
Cc: usrp-users <[email protected]>
Subject: Re: [USRP-users] Daughter board with a log response
Message-ID:
<CAGNcrNJ7mp=j81zad8ouept93ljsun830e_jxhjvjsicqif...@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
Hello
We are feeding a pulse modulated signal at 1090 MHz to the input of the
N200 and looking at the output using Gnuradio companion. The GRC flowgraph
is really simple and it contains a USRP source, few throttle blocks, a
complex to magnitude block (which is essentially doing sqrt(I*I + Q*Q)) and
looking at the output voltage using a scope sink. We start with an input
power of -80 dbm and increase it in steps of 5 and observe the output
voltage (in mv). We take these values of input power vs output voltage and
plot it in Excel. I think the receiver was saturating around -30 dbm when
the observed output voltage was around 1340mv.
On Fri, Apr 10, 2015 at 1:12 PM, Marcus D. Leech via USRP-users <
[email protected]> wrote:
> On 04/10/2015 12:33 PM, John Keller via USRP-users wrote:
>
>
> Hello
>
> We are using a USRP N200 that has a DBSR2X daughter board. We are
> decoding signals at 1090 MHz that have a very large dynamic range Our old
> system used receivers that had log amps with a dynamic range of over 80 db
> and are linear when you plot input power vs output amplitude.
>
> We plotted the output of the DBSR2X using a signal generator as an input
> source. We then plotted the input power vs output amplitude and it is very
> non linear. Do you have a daughter board with a log characteristic or could
> you suggest another way.
>
> Thank you.
>
> Regards,
>
> John Keller
>
>
> _______________________________________________
> USRP-users mailing
> [email protected]http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>
> How are you plotting this?
>
> The power of a signal is proportional to the square of the voltage. The
> DBSRX2 receiver should be very linear, except at the very upper end,
> perhaps.
>
> Logarithmic amplifier chains are generally *ONLY* used in
> high-dynamic-range power detection, they aren't general-purpose RF
> subsystems.
>
> The DBSRX2 on an N200 should have more than 80dB of dynamic range,
> depending on sample rates, and bandwidth settings of the DBSRX2 card.
>
> The instantaneous power of a signal can be calculated using:
>
> P = (I*I)+(Q*Q)
>
> Square-root and average to taste.
>
> So, what is it that you're actually measuring and plotting? The DBSRX2
> should be quite linear over a fairly large dynamic range.
>
>
>
>
> _______________________________________________
> USRP-users mailing list
> [email protected]
> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>
>
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Message: 10
Date: Fri, 10 Apr 2015 16:40:07 -0400
From: "Marcus D. Leech" <[email protected]>
To: Venkatesh Sandilya <[email protected]>, "[email protected]"
<[email protected]>
Cc: usrp-users <[email protected]>
Subject: Re: [USRP-users] Daughter board with a log response
Message-ID: <[email protected]>
Content-Type: text/plain; charset="utf-8"; Format="flowed"
On 04/10/2015 04:17 PM, Venkatesh Sandilya wrote:
> Hello
>
> We are feeding a pulse modulated signal at 1090 MHz to the input of
> the N200 and looking at the output using Gnuradio companion. The GRC
> flowgraph is really simple and it contains a USRP source, few throttle
> blocks, a complex to magnitude block (which is essentially doing
> sqrt(I*I + Q*Q)) and looking at the output voltage using a scope sink.
> We start with an input power of -80 dbm and increase it in steps of 5
> and observe the output voltage (in mv). We take these values of input
> power vs output voltage and plot it in Excel. I think the receiver was
> saturating around -30 dbm when the observed output voltage was around
> 1340mv.
Turn the gain down on the DBSRX2.
Also you say "when the observed output voltage was around 1340mV". Since
you don't get to see any absolute voltage values on the digital side,
just magnitude values that are *proportional* to the input voltage at
the antenna, I'm curious as to how you derived your 1340mV value?
The ADCs on the USRP motherboard are set with 1.2V references, so the
highest value that can be "seen" at the ADC input would be 1200mV, but this
is *AFTER* downconversion and gain and baseband filtering. You
typically have a *lot* of gain ahead of the ADCs.
So, I'd start with an input power level of around -110dBm, and work your
way up from there. It doesn't surprise me that -30dBml, with some
non-trivial
amount of gain on your DBSRX2 produces an output from the DBSRX2 that
saturates the ADCs.
>
> On Fri, Apr 10, 2015 at 1:12 PM, Marcus D. Leech via USRP-users
> <[email protected] <mailto:[email protected]>> wrote:
>
> On 04/10/2015 12:33 PM, John Keller via USRP-users wrote:
>> Hello
>> We are using a USRP N200 that has a DBSR2X daughter board. We
>> are decoding signals at 1090 MHz that have a very large dynamic
>> range Our old system used receivers that had log amps with a
>> dynamic range of over 80 db and are linear when you plot input
>> power vs output amplitude.
>> We plotted the output of the DBSR2X using a signal generator as
>> an input source. We then plotted the input power vs output
>> amplitude and it is very non linear. Do you have a daughter board
>> with a log characteristic or could you suggest another way.
>> Thank you.
>> Regards,
>> John Keller
>>
>>
>> _______________________________________________
>> USRP-users mailing list
>> [email protected] <mailto:[email protected]>
>> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
> How are you plotting this?
>
> The power of a signal is proportional to the square of the
> voltage. The DBSRX2 receiver should be very linear, except at the
> very upper end, perhaps.
>
> Logarithmic amplifier chains are generally *ONLY* used in
> high-dynamic-range power detection, they aren't general-purpose RF
> subsystems.
>
> The DBSRX2 on an N200 should have more than 80dB of dynamic range,
> depending on sample rates, and bandwidth settings of the DBSRX2 card.
>
> The instantaneous power of a signal can be calculated using:
>
> P = (I*I)+(Q*Q)
>
> Square-root and average to taste.
>
> So, what is it that you're actually measuring and plotting? The
> DBSRX2 should be quite linear over a fairly large dynamic range.
>
>
>
>
> _______________________________________________
> USRP-users mailing list
> [email protected] <mailto:[email protected]>
> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>
>
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Message: 11
Date: Fri, 10 Apr 2015 14:21:07 -0700
From: Ian Buckley <[email protected]>
To: Venkatesh Sandilya <[email protected]>
Cc: usrp-users <[email protected]>
Subject: Re: [USRP-users] Daughter board with a log response
Message-ID: <[email protected]>
Content-Type: text/plain; charset="windows-1252"
Just one other point: Throttle blocks. You should't have any in a flow graph
that contains *real* hardware?the sample rate of the USRP will pace the flow
graph. Throttle blocks are generally intended for flow graphs that contain no
real H/W, where otherwise the flow graph will consume all available system CPU.
On Apr 10, 2015, at 1:40 PM, "Marcus D. Leech via USRP-users"
<[email protected]> wrote:
> On 04/10/2015 04:17 PM, Venkatesh Sandilya wrote:
>> Hello
>>
>> We are feeding a pulse modulated signal at 1090 MHz to the input of the N200
>> and looking at the output using Gnuradio companion. The GRC flowgraph is
>> really simple and it contains a USRP source, few throttle blocks, a complex
>> to magnitude block (which is essentially doing sqrt(I*I + Q*Q)) and looking
>> at the output voltage using a scope sink. We start with an input power of
>> -80 dbm and increase it in steps of 5 and observe the output voltage (in
>> mv). We take these values of input power vs output voltage and plot it in
>> Excel. I think the receiver was saturating around -30 dbm when the observed
>> output voltage was around 1340mv.
> Turn the gain down on the DBSRX2.
>
> Also you say "when the observed output voltage was around 1340mV". Since you
> don't get to see any absolute voltage values on the digital side,
> just magnitude values that are *proportional* to the input voltage at the
> antenna, I'm curious as to how you derived your 1340mV value?
>
> The ADCs on the USRP motherboard are set with 1.2V references, so the highest
> value that can be "seen" at the ADC input would be 1200mV, but this
> is *AFTER* downconversion and gain and baseband filtering. You typically
> have a *lot* of gain ahead of the ADCs.
>
> So, I'd start with an input power level of around -110dBm, and work your way
> up from there. It doesn't surprise me that -30dBml, with some non-trivial
> amount of gain on your DBSRX2 produces an output from the DBSRX2 that
> saturates the ADCs.
>
>
>>
>> On Fri, Apr 10, 2015 at 1:12 PM, Marcus D. Leech via USRP-users
>> <[email protected]> wrote:
>> On 04/10/2015 12:33 PM, John Keller via USRP-users wrote:
>>>
>>> Hello
>>>
>>> We are using a USRP N200 that has a DBSR2X daughter board. We are
>>> decoding signals at 1090 MHz that have a very large dynamic range Our old
>>> system used receivers that had log amps with a dynamic range of over 80 db
>>> and are linear when you plot input power vs output amplitude.
>>>
>>> We plotted the output of the DBSR2X using a signal generator as an input
>>> source. We then plotted the input power vs output amplitude and it is very
>>> non linear. Do you have a daughter board with a log characteristic or could
>>> you suggest another way.
>>>
>>> Thank you.
>>>
>>> Regards,
>>>
>>> John Keller
>>>
>>>
>>> _______________________________________________
>>> USRP-users mailing list
>>> [email protected]
>>> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>> How are you plotting this?
>>
>> The power of a signal is proportional to the square of the voltage. The
>> DBSRX2 receiver should be very linear, except at the very upper end, perhaps.
>>
>> Logarithmic amplifier chains are generally *ONLY* used in high-dynamic-range
>> power detection, they aren't general-purpose RF subsystems.
>>
>> The DBSRX2 on an N200 should have more than 80dB of dynamic range, depending
>> on sample rates, and bandwidth settings of the DBSRX2 card.
>>
>> The instantaneous power of a signal can be calculated using:
>>
>> P = (I*I)+(Q*Q)
>>
>> Square-root and average to taste.
>>
>> So, what is it that you're actually measuring and plotting? The DBSRX2
>> should be quite linear over a fairly large dynamic range.
>>
>>
>>
>>
>> _______________________________________________
>> USRP-users mailing list
>> [email protected]
>> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>>
>>
>
> _______________________________________________
> USRP-users mailing list
> [email protected]
> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
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Message: 12
Date: Fri, 10 Apr 2015 14:23:34 -0700
From: Tom Tsou <[email protected]>
To: "Ralph A. Schmid, dk5ras" <[email protected]>
Cc: "[email protected]" <[email protected]>,
"[email protected]"
<[email protected]>
Subject: Re: [USRP-users] [Openbts-discuss] new uhd breaks uplink?
Message-ID:
<caatym+b0szhbx5uayde+rvnqvemuaeu7rp_eq9kdyufuqdn...@mail.gmail.com>
Content-Type: text/plain; charset=UTF-8
Hi Ralph,
On Fri, Apr 10, 2015 at 8:48 AM, Ralph A. Schmid, dk5ras via
USRP-users <[email protected]> wrote:
> OK, sounds like a reasonable explanation. So I simply will stay with a
> release behind and wait what will happen :)
Confirmed that the FPGA filter change that Ian mentioned has modified
slot timing.
Once the new release of UHD gets tagged, I'll add timing compensation
values that will be version detected at build time.
-TT
------------------------------
Message: 13
Date: Fri, 10 Apr 2015 17:25:58 -0400
From: Venkatesh Sandilya <[email protected]>
To: Ian Buckley <[email protected]>
Cc: usrp-users <[email protected]>
Subject: Re: [USRP-users] Daughter board with a log response
Message-ID:
<cagncrn+e02gs1ec9jopw5u2b4h9rkxrau0m8f0_b9pxn5qr...@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
I understand. I realize that now about the throttle blocks. Will experiment
without them and see if that makes a difference.
On Apr 10, 2015 5:21 PM, "Ian Buckley" <[email protected]> wrote:
> Just one other point: Throttle blocks. You should't have any in a flow
> graph that contains *real* hardware?the sample rate of the USRP will pace
> the flow graph. Throttle blocks are generally intended for flow graphs that
> contain no real H/W, where otherwise the flow graph will consume all
> available system CPU.
>
> On Apr 10, 2015, at 1:40 PM, "Marcus D. Leech via USRP-users" <
> [email protected]> wrote:
>
> On 04/10/2015 04:17 PM, Venkatesh Sandilya wrote:
>
> Hello
>
> We are feeding a pulse modulated signal at 1090 MHz to the input of the
> N200 and looking at the output using Gnuradio companion. The GRC flowgraph
> is really simple and it contains a USRP source, few throttle blocks, a
> complex to magnitude block (which is essentially doing sqrt(I*I + Q*Q)) and
> looking at the output voltage using a scope sink. We start with an input
> power of -80 dbm and increase it in steps of 5 and observe the output
> voltage (in mv). We take these values of input power vs output voltage and
> plot it in Excel. I think the receiver was saturating around -30 dbm when
> the observed output voltage was around 1340mv.
>
> Turn the gain down on the DBSRX2.
>
> Also you say "when the observed output voltage was around 1340mV". Since
> you don't get to see any absolute voltage values on the digital side,
> just magnitude values that are *proportional* to the input voltage at
> the antenna, I'm curious as to how you derived your 1340mV value?
>
> The ADCs on the USRP motherboard are set with 1.2V references, so the
> highest value that can be "seen" at the ADC input would be 1200mV, but this
> is *AFTER* downconversion and gain and baseband filtering. You
> typically have a *lot* of gain ahead of the ADCs.
>
> So, I'd start with an input power level of around -110dBm, and work your
> way up from there. It doesn't surprise me that -30dBml, with some
> non-trivial
> amount of gain on your DBSRX2 produces an output from the DBSRX2 that
> saturates the ADCs.
>
>
>
> On Fri, Apr 10, 2015 at 1:12 PM, Marcus D. Leech via USRP-users <
> [email protected]> wrote:
>
>> On 04/10/2015 12:33 PM, John Keller via USRP-users wrote:
>>
>>
>> Hello
>>
>> We are using a USRP N200 that has a DBSR2X daughter board. We are
>> decoding signals at 1090 MHz that have a very large dynamic range Our old
>> system used receivers that had log amps with a dynamic range of over 80 db
>> and are linear when you plot input power vs output amplitude.
>>
>> We plotted the output of the DBSR2X using a signal generator as an input
>> source. We then plotted the input power vs output amplitude and it is very
>> non linear. Do you have a daughter board with a log characteristic or could
>> you suggest another way.
>>
>> Thank you.
>>
>> Regards,
>>
>> John Keller
>>
>>
>> _______________________________________________
>> USRP-users mailing
>> [email protected]http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>>
>> How are you plotting this?
>>
>> The power of a signal is proportional to the square of the voltage. The
>> DBSRX2 receiver should be very linear, except at the very upper end,
>> perhaps.
>>
>> Logarithmic amplifier chains are generally *ONLY* used in
>> high-dynamic-range power detection, they aren't general-purpose RF
>> subsystems.
>>
>> The DBSRX2 on an N200 should have more than 80dB of dynamic range,
>> depending on sample rates, and bandwidth settings of the DBSRX2 card.
>>
>> The instantaneous power of a signal can be calculated using:
>>
>> P = (I*I)+(Q*Q)
>>
>> Square-root and average to taste.
>>
>> So, what is it that you're actually measuring and plotting? The DBSRX2
>> should be quite linear over a fairly large dynamic range.
>>
>>
>>
>>
>> _______________________________________________
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>> [email protected]
>> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>>
>>
>
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>
>
>
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