[USRP-users] Output power of E310

Claudio Cicconetti ccicconetti at mbigroup.it
Thu Mar 17 09:54:40 EDT 2016


Dear Marcus(es), all,
I think we may have found the issue.

In all the experiments (*) we configured the radio with maximum gain.

In fact, both intuition and the analysis of performance data for
CBX/WBX/etc daughterboards suggest that max output power is reached with
maximum gain.

However, with out E310 at 1.5 GHz we reach an absolute maximum of 8.5 dB
(which is OK according to the AD9361 specs) with a gain value around 75
dB, then the output power drops significantly: at maximum gain, i.e.,
98.75 dB, the output power is 25 dB smaller than at 75 dB!

This happens with three different E310 firmware releases, including
latest Release-4 from git repository.

We are quite happy of the finding, but I would be curious to know
whether anyone else has observed this output power drop or if it is
anyway expected.

Best regards,
Claudio

(*) Transmission was done with UHD's tx_waveform example for easier
independent repetition.

(**) Output power was measured with both an Agilent spectrum analyzer
and a National Instrument power meter


On 03/15/2016 05:58 PM, mleech at ripnet.com wrote:
>  
> 
> I think it would be hard to get them correct in all cases, for example,
> when a signal straddles a boundary and is wide enough that the resulting
> passband is nowhere-near flat. 
> 
> Near as I can tell, the filter selections are correct in the UHD code. 
> 
> Now, as to why you're getting low output powers at some frequencies
> (very much below what one would expect), that's not clear. 
> 
> If you use something simple, like uhd_tx_waveform, at various center
> frequencies (the ones you listed), what are your results? 
> 
> On 2016-03-15 12:37, Claudio Cicconetti via USRP-users wrote: 
> 
>> Dear Marcus,
>> I suppose modifying the UHD code would not be a blocking issue (though
>> having an API would definitely make one's life easier): by following a
>> mix of manual + Philip instructions I was able to build an image from
>> source code.
>>
>> However, I am still not getting if the current implementation of the
>> filter boundaries are i) wrong, or ii) wrong under some circumstances
>> such as mine, or iii) correct for all cases but I am missing something else.
>>
>> Best regards,
>> Claudio
>>
>> On 03/15/2016 05:30 PM, Marcus Müller via USRP-users wrote:
>> The point still is that to change the boundaries at which a different filter is used, you'd have to modify UHD's e300_impl.cpp around lines 1160ff. UHD currently doesn't expose an API to do so. On 03/15/2016 04:30 PM, Marcus D. Leech via USRP-users wrote: Ah, found it. There's an update_bandsel() method in e300_impl.cpp On 2016-03-15 11:23, Marcus D. Leech via USRP-users wrote: Claudio: I'm hunting through the code to see where it selects the filters based on frequency. All of this code was recently re-factored, and I have a query in to R&D to figure this out. There doesn't appear to be a top-level "set_filter()" although such is used internally in the drivers, which select the appropriate filters automatically. On 2016-03-15 07:15, Claudio Cicconetti wrote: Dear Marcus, all, I have upgraded to latest (Rev4) image, the results are basically the same: output power varies significantly and non-monotonically with center frequency. Is there any (simple) way to change the configuration

> of filters? Finding a "good" configuration for a given frequency with trial&error would be acceptable for us, since the center frequency is fixed and known in advance. Btw, I tried to generate the image from source following the instructions in the manual, but the compilation fails ('unknown type name' errors when compiling volk). Best regards, Claudio On 03/14/2016 02:25 PM, Marcus D. Leech via USRP-users wrote: On 03/14/2016 04:04 AM, Claudio Cicconetti via USRP-users wrote: 2. getting a pre-built image from http://files.ettus.com/e3xx_images/ [1] If the option 2. is the correct one, can you please provide a pointer to the correct image to copy to the SD? I'd use the latest Rev4 image: http://files.ettus.com/e3xx_images/e3xx-release-4/ettus-e3xx-sg1/ [2] Use the "dev" image Best regards, Claudio _______________________________________________ USRP-users mailing list USRP-users at lists.ettus.com <mailto:USRP-users at lists.ettus.com>
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> Links:
> ------
> [1] http://files.ettus.com/e3xx_images/
> [2] http://files.ettus.com/e3xx_images/e3xx-release-4/ettus-e3xx-sg1/
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