Re: [USRP-users] USRP N310 Receiver Noise Floor, Sensitivity

[Marcus D. Leech via USRP-users]

On 05/13/2018 08:45 PM, David Bengtson wrote:
On a side note, the combination of wideband LNA's in front of wideband 
radios is generally something to be careful of, as strong signals out 
of band can cause problems. Bandpass filtering in front of LNA's can 
be a very good idea to think about. 
The only caution I have about filtering *IN FRONT* of an LNA is that the 
loss through the filter is usually enough to turn your

  LNA into just an "A" :)

The approach that I use for radio astronomy is to place the 
highest-dynamic-range LNA "out front", then immediately filter, some 
more gain, some

  more filtering, then the radio

In some circumstances, of course, you simply have to pay the noise 
penalty of having a filter between your antenna and the first gain stage.
  We do this at CCERA for our 611MHz interferometer, because there's 
just SO MUCH adjacent crap.  I had some multi-stage cavity filters made
  in China for me, and they're about 1.5dB insertion loss.  But 
followed by a 0.5dB LNA, it's still "low enough" noise to do what we 
need it to do.


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Re: [USRP-users] USRP N310 Receiver Noise Floor, Sensitivity

[David Bengtson via USRP-users]

On Sun, May 13, 2018 at 4:34 PM, Marcus D. Leech via USRP-users
 wrote:
> On 05/13/2018 04:25 PM, Zhongyuan Zhao wrote:
>
> Thank you for the response.  3.6dB NF is not impressive however I was
> considering a wideband LNA as an once-for-all solution for the entire
> frequency range 50-6000MHz of N310.
>
> Let me re-phrase the question in two different ways:
> 1) What is the minimal discernible signal (MDS) at the input of the N310
> receiver if no external LNA is used?
>
> I don't think there are measured specs out there yet, but my experience in
> the past with most of these radios is that the narrowband MDS is
>   usually better than -120dBm at max gain over most of the operating
> envelope.
>
Part of the question is that MDS in these radios includes the digital
demodulation portion. In narrow band analog radios with an analog IF
stage, you could use
a voltmeter to measure the analog voltage present to determine an MDS.
With a Terminated input, you would measure the analog noise floor,
then add a known signal and measure the input signal needed to add 3
dB to the analog noise floor, which gave you a close measurement to
the radio noise floor, as well as a way to determine the MDS.

Digital radios make is more difficult to do this because of the
digital processing involved. MDS is heavily dependent on the type of
modulation as well as the performance of the demodulator. This is
something you're going to have to figure out. For example, spread
spectrum signals (GPS, for example) can be demodulated with signals
that are 15 to 20 dB below the noise floor, so something you couldn't
see on a spectrum analyzer.

Marcus's comment of a narrowband (25 kHz Channel type of narrowband)
matches well with the work I've done with analog radios with 2 to 3 dB
noise floor, so the quoted 5.8 dB noise floor for the N310 sounds
about right.

On a side note, the combination of wideband LNA's in front of wideband
radios is generally something to be careful of, as strong signals out
of band can cause problems. Bandpass filtering in front of LNA's can
be a very good idea to think about.

>
> 2) If only thermal noise is fed into the N310 receiver, (-103.9dBm for 10MHz
> bandwidth) what is the output power or power spectrum density (dBm/Hz) at
> the output of receiver? Suppose the calibration between dBFS and dBm is done
> correctly. In theory, a receiver with Noise Figure of 5.8dB adds 5.8dB to
> input noise, therefore output power of the receiver would be -98.1dBm.
> However I am not quite sure about if this is applicable to near thermal
> noise floor. A spectrum analyzer has a NF of 3dB but the noise floor
> displayed might be 20dB above the thermal noise floor.
>
> There is usually some non-linearity measuring very close to the noise floor.
>
> If you have an N310 and a decent lab (I assume that the UNL electronics lab
> has things like calibrated noise sources, etc), then you can answer these
>   questions yourself.
>
>
>
>
> I am especially interested in the band of 500-1000MHz, but answers for other
> bands are helpful as well.
>
> Many thanks!
>
> Zhongyuan Zhao
>
> PhD Candidate,
> Department of Computer Science & Engineering,
> University of Nebraska-Lincoln
> Office Hour: WF 9:30-10:00am, Avery Hall 12,
> Suite 117, Schorr Center,
> Lincoln, Nebraska 68588-0115
>
>
> On Sun, May 13, 2018 at 2:36 PM, Marcus D. Leech via USRP-users
>  wrote:
>>
>> On 05/13/2018 03:24 PM, David Bengtson via USRP-users wrote:
>>>
>>> The Receiver Noise figure should include sampling noise and ADC ENOB.
>>> Is that a free space path loss? You don't have any design margin for
>>> fades/blockages etc, so an External LNA might be a good idea. 3.6 dB
>>> NF isn't particularly low for a LNA, but it will help.
>>
>> Technically, the equivalent noise figure of the ADC is "swamped" by the
>> gain stages ahead of the ADC.
>>
>> System noise chain analysis usually (not always) gets increasingly boring
>> the further away from the antenna you get, because noise figures
>>   of "deep" stages are diluted considerably by the aggregate gain of the
>> stages ahead of them...
>>
>>
>>
>>> On Sun, May 13, 2018 at 3:49 AM, Zhongyuan Zhao via USRP-users
>>>  wrote:

 Hi,

 I am trying to calculate the link budget for USRP N310.

 Suppose I want a SNR of 20dB,
 the signal bandwidth is 10MHz,
 the thermal noise floor is -103.9dm.
 Receiver noise figure is 5.8dB (N310 datasheet 5.8dB @1.8GHz)
 Rx Antenna Gain 6dBi
 Path loss: 120dB
 Tx Antenna Gain 6dBi
 RF cable Loss (RX+TX): 1dB

 Then my TX power before TX antenna should be
 -103.9dBm + 20dB + 5.8dB - 6dBi + 120dB -6dBi + 1dB = 30.9dBm

 The receive signal strength at RX port of USRP = -78.1dBm
 The noise strength at RX port of USRP = -103.9dBm
 The SNR before receiver is 25.8dB, after receiver is 20dB.

 However, due to the sampling noise and effective bits of ADC, I doubt
 that
 the noise floor after the receiver 

Re: [USRP-users] USRP N310 Receiver Noise Floor, Sensitivity

[Marcus D. Leech via USRP-users]

On 05/13/2018 04:25 PM, Zhongyuan Zhao wrote:
Thank you for the response.  3.6dB NF is not impressive however I was 
considering a wideband LNA as an once-for-all solution for the entire 
frequency range 50-6000MHz of N310.


Let me re-phrase the question in two different ways:
1) What is the minimal discernible signal (MDS) at the input of the 
N310 receiver if no external LNA is used?
I don't think there are measured specs out there yet, but my experience 
in the past with most of these radios is that the narrowband MDS is
  usually better than -120dBm at max gain over most of the operating 
envelope.




2) If only thermal noise is fed into the N310 receiver, (-103.9dBm for 
10MHz bandwidth) what is the output power or power spectrum density 
(dBm/Hz) at the output of receiver? Suppose the calibration between 
dBFS and dBm is done correctly. In theory, a receiver with Noise 
Figure of 5.8dB adds 5.8dB to input noise, therefore output power of 
the receiver would be -98.1dBm. However I am not quite sure about if 
this is applicable to near thermal noise floor. A spectrum analyzer 
has a NF of 3dB but the noise floor displayed might be 20dB above the 
thermal noise floor.

There is usually some non-linearity measuring very close to the noise floor.

If you have an N310 and a decent lab (I assume that the UNL electronics 
lab has things like calibrated noise sources, etc), then you can answer 
these

  questions yourself.




I am especially interested in the band of 500-1000MHz, but answers for 
other bands are helpful as well.


Many thanks!

Zhongyuan Zhao

PhD Candidate,
Department of Computer Science & Engineering,
University of Nebraska-Lincoln
Office Hour: WF 9:30-10:00am, Avery Hall 12,
Suite 117, Schorr Center,
Lincoln, Nebraska 68588-0115


On Sun, May 13, 2018 at 2:36 PM, Marcus D. Leech via USRP-users 
mailto:usrp-users@lists.ettus.com>> wrote:


On 05/13/2018 03:24 PM, David Bengtson via USRP-users wrote:

The Receiver Noise figure should include sampling noise and
ADC ENOB.
Is that a free space path loss? You don't have any design
margin for
fades/blockages etc, so an External LNA might be a good idea.
3.6 dB
NF isn't particularly low for a LNA, but it will help.

Technically, the equivalent noise figure of the ADC is "swamped"
by the gain stages ahead of the ADC.

System noise chain analysis usually (not always) gets increasingly
boring the further away from the antenna you get, because noise
figures
  of "deep" stages are diluted considerably by the aggregate gain
of the stages ahead of them...



On Sun, May 13, 2018 at 3:49 AM, Zhongyuan Zhao via USRP-users
mailto:usrp-users@lists.ettus.com>> wrote:

Hi,

I am trying to calculate the link budget for USRP N310.

Suppose I want a SNR of 20dB,
the signal bandwidth is 10MHz,
the thermal noise floor is -103.9dm.
Receiver noise figure is 5.8dB (N310 datasheet 5.8dB @1.8GHz)
Rx Antenna Gain 6dBi
Path loss: 120dB
Tx Antenna Gain 6dBi
RF cable Loss (RX+TX): 1dB

Then my TX power before TX antenna should be
-103.9dBm + 20dB + 5.8dB - 6dBi + 120dB -6dBi + 1dB = 30.9dBm

The receive signal strength at RX port of USRP = -78.1dBm
The noise strength at RX port of USRP = -103.9dBm
The SNR before receiver is 25.8dB, after receiver is 20dB.

However, due to the sampling noise and effective bits of
ADC, I doubt that
the noise floor after the receiver would be much higher
than -103.9dBm +
5.8dB = -98.1dBm, e.g. -90dBm?, in that case my receive
SNR would be lower
than 20dB.

Does anyone know the output noise floor (or sensitivity)
of USRP N310
receiver (e.g. RX2 port) in 500-1000MHz band? e.g. in the
unit of dBm/Hz?

That would help me to decide if an external LNA is
necessary. If so does
some typical wideband LNA with a gain of 20dB and noise
figure of 3.6dB
would be enough.


Thank you!

Regards,
Zhongyuan Zhao

PhD Candidate,
Department of Computer Science & Engineering,
University of Nebraska-Lincoln


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Re: [USRP-users] USRP N310 Receiver Noise Floor, Sensitivity

[Zhongyuan Zhao via USRP-users]

Thank you for the response.  3.6dB NF is not impressive however I was
considering a wideband LNA as an once-for-all solution for the entire
frequency range 50-6000MHz of N310.

Let me re-phrase the question in two different ways:
1) What is the minimal discernible signal (MDS) at the input of the N310
receiver if no external LNA is used?

2) If only thermal noise is fed into the N310 receiver, (-103.9dBm for
10MHz bandwidth) what is the output power or power spectrum density
(dBm/Hz) at the output of receiver? Suppose the calibration between dBFS
and dBm is done correctly. In theory, a receiver with Noise Figure of 5.8dB
adds 5.8dB to input noise, therefore output power of the receiver would be
-98.1dBm. However I am not quite sure about if this is applicable to near
thermal noise floor. A spectrum analyzer has a NF of 3dB but the noise
floor displayed might be 20dB above the thermal noise floor.

I am especially interested in the band of 500-1000MHz, but answers for
other bands are helpful as well.

Many thanks!

Zhongyuan Zhao

PhD Candidate,
Department of Computer Science & Engineering,
University of Nebraska-Lincoln
Office Hour: WF 9:30-10:00am, Avery Hall 12,
Suite 117, Schorr Center,
Lincoln, Nebraska 68588-0115


On Sun, May 13, 2018 at 2:36 PM, Marcus D. Leech via USRP-users <
usrp-users@lists.ettus.com> wrote:

> On 05/13/2018 03:24 PM, David Bengtson via USRP-users wrote:
>
>> The Receiver Noise figure should include sampling noise and ADC ENOB.
>> Is that a free space path loss? You don't have any design margin for
>> fades/blockages etc, so an External LNA might be a good idea. 3.6 dB
>> NF isn't particularly low for a LNA, but it will help.
>>
> Technically, the equivalent noise figure of the ADC is "swamped" by the
> gain stages ahead of the ADC.
>
> System noise chain analysis usually (not always) gets increasingly boring
> the further away from the antenna you get, because noise figures
>   of "deep" stages are diluted considerably by the aggregate gain of the
> stages ahead of them...
>
>
>
> On Sun, May 13, 2018 at 3:49 AM, Zhongyuan Zhao via USRP-users
>>  wrote:
>>
>>> Hi,
>>>
>>> I am trying to calculate the link budget for USRP N310.
>>>
>>> Suppose I want a SNR of 20dB,
>>> the signal bandwidth is 10MHz,
>>> the thermal noise floor is -103.9dm.
>>> Receiver noise figure is 5.8dB (N310 datasheet 5.8dB @1.8GHz)
>>> Rx Antenna Gain 6dBi
>>> Path loss: 120dB
>>> Tx Antenna Gain 6dBi
>>> RF cable Loss (RX+TX): 1dB
>>>
>>> Then my TX power before TX antenna should be
>>> -103.9dBm + 20dB + 5.8dB - 6dBi + 120dB -6dBi + 1dB = 30.9dBm
>>>
>>> The receive signal strength at RX port of USRP = -78.1dBm
>>> The noise strength at RX port of USRP = -103.9dBm
>>> The SNR before receiver is 25.8dB, after receiver is 20dB.
>>>
>>> However, due to the sampling noise and effective bits of ADC, I doubt
>>> that
>>> the noise floor after the receiver would be much higher than -103.9dBm +
>>> 5.8dB = -98.1dBm, e.g. -90dBm?, in that case my receive SNR would be
>>> lower
>>> than 20dB.
>>>
>>> Does anyone know the output noise floor (or sensitivity) of USRP N310
>>> receiver (e.g. RX2 port) in 500-1000MHz band? e.g. in the unit of dBm/Hz?
>>>
>>> That would help me to decide if an external LNA is necessary. If so does
>>> some typical wideband LNA with a gain of 20dB and noise figure of 3.6dB
>>> would be enough.
>>>
>>>
>>> Thank you!
>>>
>>> Regards,
>>> Zhongyuan Zhao
>>>
>>> PhD Candidate,
>>> Department of Computer Science & Engineering,
>>> University of Nebraska-Lincoln
>>>
>>>
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>
>
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Re: [USRP-users] USRP N310 Receiver Noise Floor, Sensitivity

[Marcus D. Leech via USRP-users]

On 05/13/2018 03:24 PM, David Bengtson via USRP-users wrote:

The Receiver Noise figure should include sampling noise and ADC ENOB.
Is that a free space path loss? You don't have any design margin for
fades/blockages etc, so an External LNA might be a good idea. 3.6 dB
NF isn't particularly low for a LNA, but it will help.
Technically, the equivalent noise figure of the ADC is "swamped" by the 
gain stages ahead of the ADC.


System noise chain analysis usually (not always) gets increasingly 
boring the further away from the antenna you get, because noise figures
  of "deep" stages are diluted considerably by the aggregate gain of 
the stages ahead of them...




On Sun, May 13, 2018 at 3:49 AM, Zhongyuan Zhao via USRP-users
 wrote:

Hi,

I am trying to calculate the link budget for USRP N310.

Suppose I want a SNR of 20dB,
the signal bandwidth is 10MHz,
the thermal noise floor is -103.9dm.
Receiver noise figure is 5.8dB (N310 datasheet 5.8dB @1.8GHz)
Rx Antenna Gain 6dBi
Path loss: 120dB
Tx Antenna Gain 6dBi
RF cable Loss (RX+TX): 1dB

Then my TX power before TX antenna should be
-103.9dBm + 20dB + 5.8dB - 6dBi + 120dB -6dBi + 1dB = 30.9dBm

The receive signal strength at RX port of USRP = -78.1dBm
The noise strength at RX port of USRP = -103.9dBm
The SNR before receiver is 25.8dB, after receiver is 20dB.

However, due to the sampling noise and effective bits of ADC, I doubt that
the noise floor after the receiver would be much higher than -103.9dBm +
5.8dB = -98.1dBm, e.g. -90dBm?, in that case my receive SNR would be lower
than 20dB.

Does anyone know the output noise floor (or sensitivity) of USRP N310
receiver (e.g. RX2 port) in 500-1000MHz band? e.g. in the unit of dBm/Hz?

That would help me to decide if an external LNA is necessary. If so does
some typical wideband LNA with a gain of 20dB and noise figure of 3.6dB
would be enough.


Thank you!

Regards,
Zhongyuan Zhao

PhD Candidate,
Department of Computer Science & Engineering,
University of Nebraska-Lincoln


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Re: [USRP-users] USRP N310 Receiver Noise Floor, Sensitivity

[David Bengtson via USRP-users]

The Receiver Noise figure should include sampling noise and ADC ENOB.
Is that a free space path loss? You don't have any design margin for
fades/blockages etc, so an External LNA might be a good idea. 3.6 dB
NF isn't particularly low for a LNA, but it will help.

On Sun, May 13, 2018 at 3:49 AM, Zhongyuan Zhao via USRP-users
 wrote:
> Hi,
>
> I am trying to calculate the link budget for USRP N310.
>
> Suppose I want a SNR of 20dB,
> the signal bandwidth is 10MHz,
> the thermal noise floor is -103.9dm.
> Receiver noise figure is 5.8dB (N310 datasheet 5.8dB @1.8GHz)
> Rx Antenna Gain 6dBi
> Path loss: 120dB
> Tx Antenna Gain 6dBi
> RF cable Loss (RX+TX): 1dB
>
> Then my TX power before TX antenna should be
> -103.9dBm + 20dB + 5.8dB - 6dBi + 120dB -6dBi + 1dB = 30.9dBm
>
> The receive signal strength at RX port of USRP = -78.1dBm
> The noise strength at RX port of USRP = -103.9dBm
> The SNR before receiver is 25.8dB, after receiver is 20dB.
>
> However, due to the sampling noise and effective bits of ADC, I doubt that
> the noise floor after the receiver would be much higher than -103.9dBm +
> 5.8dB = -98.1dBm, e.g. -90dBm?, in that case my receive SNR would be lower
> than 20dB.
>
> Does anyone know the output noise floor (or sensitivity) of USRP N310
> receiver (e.g. RX2 port) in 500-1000MHz band? e.g. in the unit of dBm/Hz?
>
> That would help me to decide if an external LNA is necessary. If so does
> some typical wideband LNA with a gain of 20dB and noise figure of 3.6dB
> would be enough.
>
>
> Thank you!
>
> Regards,
> Zhongyuan Zhao
>
> PhD Candidate,
> Department of Computer Science & Engineering,
> University of Nebraska-Lincoln
>
>
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