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Today's Topics:
1. Re: Full scale current output of the DAC for USRP n210
(Marcus D. Leech)
2. Re: Full scale current output of the DAC for USRP n210 (Usrp IITM)
3. Re: Full scale current output of the DAC for USRP n210
(Marcus D. Leech)
----------------------------------------------------------------------
Message: 1
Date: Sat, 05 Jan 2013 12:06:45 -0500
From: "Marcus D. Leech" <[email protected]>
To: [email protected]
Subject: Re: [USRP-users] Full scale current output of the DAC for
USRP n210
Message-ID: <[email protected]>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
On 01/05/2013 08:57 AM, Usrp IITM wrote:
> So does the 20ma correspond(approximately) to the maximum digital
> input amplitude (signal value 1.0 at the host)?
>
>
> Also, is it correct that the maximum signal (I and Q) input to the
> mixer (ADL 5375-05) is 1 V peak to peak and corresponds to the 20ma?
>
> -Regards
> RK
You haven't stated which daughterboard you're talking about. There's no
mixer, that I'm aware of, on the N210 motherboard, so you must
be referring to a daughtercard. Which one?
Also, if you're hoping to be able to set the baseband signal level and
gain, and have a strictly-reproducible signal output level, you're living in
a state of technical and statistical sin. Analog RF components have
variabilities in performance, often by as much as 1-2dB across frqeuency,
ambient temperature, and manufacturing lot numbers. They only way to
*know* what your TX output power level is going to be for any
given collection of parameters {baseband-magnitude, RF gain setting,
ambient temperature, frequency} is to *measure* with a precision
power meter, and perhaps keep calibration records for each unit, and
perhap use those to tweak your baseband implementation.
--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org
------------------------------
Message: 2
Date: Sat, 5 Jan 2013 22:54:11 +0530
From: Usrp IITM <[email protected]>
To: "Marcus D. Leech" <[email protected]>
Cc: [email protected]
Subject: Re: [USRP-users] Full scale current output of the DAC for
USRP n210
Message-ID:
<CAPkh=_8rf-9bjm1c3neql79vxxs6pzvuaipeinud-kpwpaf...@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
Sorry, I was talking about the SBX daughter board. I am trying to figure
out (ball park numbers) the relation between the input signal (at the host)
and the transmit power. I agree with your point of the variability of the
RF circuits.
However, I just want to figure out the ball park numbers by looking at the
specs of the devices on the board.
Does (roughly) the 20 ma at the DAC corresponds to the maximum input
signal of 1 at the host (computer). Or is some scaling happening in the
FPGA?
-Regards
RK
On Sat, Jan 5, 2013 at 10:36 PM, Marcus D. Leech <[email protected]> wrote:
> On 01/05/2013 08:57 AM, Usrp IITM wrote:
>
>> So does the 20ma correspond(approximately) to the maximum digital input
>> amplitude (signal value 1.0 at the host)?
>>
>>
>> Also, is it correct that the maximum signal (I and Q) input to the mixer
>> (ADL 5375-05) is 1 V peak to peak and corresponds to the 20ma?
>>
>> -Regards
>> RK
>>
> You haven't stated which daughterboard you're talking about. There's no
> mixer, that I'm aware of, on the N210 motherboard, so you must
> be referring to a daughtercard. Which one?
>
> Also, if you're hoping to be able to set the baseband signal level and
> gain, and have a strictly-reproducible signal output level, you're living in
> a state of technical and statistical sin. Analog RF components have
> variabilities in performance, often by as much as 1-2dB across frqeuency,
> ambient temperature, and manufacturing lot numbers. They only way to
> *know* what your TX output power level is going to be for any
> given collection of parameters {baseband-magnitude, RF gain setting,
> ambient temperature, frequency} is to *measure* with a precision
> power meter, and perhaps keep calibration records for each unit, and
> perhap use those to tweak your baseband implementation.
>
>
>
> --
> Marcus Leech
> Principal Investigator
> Shirleys Bay Radio Astronomy Consortium
> http://www.sbrac.org
>
>
>
>
> ______________________________**_________________
> USRP-users mailing list
> [email protected]
> http://lists.ettus.com/**mailman/listinfo/usrp-users_**lists.ettus.com<http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com>
>
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------------------------------
Message: 3
Date: Sat, 05 Jan 2013 13:13:22 -0500
From: "Marcus D. Leech" <[email protected]>
To: Usrp IITM <[email protected]>
Cc: [email protected]
Subject: Re: [USRP-users] Full scale current output of the DAC for
USRP n210
Message-ID: <[email protected]>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> Sorry, I was talking about the SBX daughter board. I am trying to
> figure out (ball park numbers) the relation between the input signal
> (at the host)
> and the transmit power. I agree with your point of the variability of
> the RF circuits.
>
> However, I just want to figure out the ball park numbers by looking
> at the specs of the devices on the board.
>
> Does (roughly) the 20 ma at the DAC corresponds to the maximum input
> signal of 1 at the host (computer). Or is some scaling happening in
> the FPGA?
>
>
1.0 at the host corresponds to full-scale (more or less) DAC output.
Keep in mind that there are interpolation filters in the FPGA, so it's all
rather approximate.
But RF output power is dependant not only on the magnitude of the
baseband signals, but also of the RF gain setting. And driving the analog
RF output stages to their absolute maximums is a good way to get
non-linearities and the attendant unwanted harmonic products in the
output.
--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org
------------------------------
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