Re: [Discuss-gnuradio] How to use IQ Bal Optimize/Fix?

[Jeff Long]

IQ balance is something that applies to a receiver or channel, not to a 
signal. Dynamic/automatic balancing is the thing that only works in 
limited situations. If you have a balance problem with a real receiver, 
you can calibrate with an off-center tone, then put the results in the 
manual fields. You may have to do this at each tuning frequency you 
expect to use. Some SDRs do this internally.

Whether this makes sense to do in a GR flowgraph depends on what you're 
trying to do.

On 02/01/2018 06:17 AM, kokosz wrote:
> Jeff, thank you for your tips. Actually I was testing it with another 
> flowgraph and was in a rush to create this simple example, that's why I 
> have fed original signal to these blocks. That's obvious mistake, thank 
> you for pointing it out.
>
> I have added sliders in order to change IQ imbalance generator settings 
> in real-time as you suggested, and I can see that "IQ Balance Optimize" 
> block is adjusting its settings. Unfortunately, the output signal is 
> terribly deformed. I guess this is the case mentioned by Sylvain and 
> Marcus, and this block cannot work with such signal. It is a pity. 
> Nevertheless, I appreciate help of all of you.
>
> Have a nice day!
>
> Dnia 31 stycznia 2018 21:25 Marcus D. Leech <address@hidden> napisał(a):
>
>     On 01/31/2018 03:16 PM, Sylvain Munaut wrote:
>
>         Hi,
>
>         * You can just use 0.0 / 0.0 as the default. Those value are only
>         really used if you don't use the message system and just want a
>         fixed
>         / known manually set correction. Once the first message is received,
>         those value are overwritten
>
>         * As stated the time constant is in samples.
>
>         * The 'optimize' block only really works when you have some narrow
>         band signals distributed around the spectrums. It will fail
>         _miserably_ if you have a single wideband signal centered around DC
>         ...
>
>         Cheers,
>
>               Sylvain
>
>     Indeed, I find that if I use the osmocom IQ-balance code on radio
>     astronomy "signals" that it produces horrible results in interferometry
>     applications, as
>       it never really "converges", and adds significant long-time-scale
>     phase-noise, so I disable it.
>
>
>
>
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