Re: Modulate Vector block and double filtration

[Marcus Müller]

Hi Marcin,

well, that flow graph only serves the purpose of pre-modulating things, e.g. for preamble 
correlation, I'd speculate that's for when you want to e.g. simulate a channel impulse 
response, or some external band-limiting filtering on your already pulse-shaped signal.

However, you're right, neither in the GRC examples nor in any test cases we have do we 
make use of that taps vector (other than `[1]` as the perfect channel).

Cheers,
Marcus

On 04.08.22 09:43, Marcin Puchlik via GNU Radio, the Free & Open-Source Toolkit for 
Software Radio wrote:
> Hello Community,
> Recently I investigated Modulate Vector 
> <https://wiki.gnuradio.org/index.php?title=Modulate_Vector> block and my observations are 
> that this block has two filtering stages - firstly in the modulator (RRC filter) and 
> secondly in itself (user providing the filter taps). The simple scheme of operation looks 
> like in the below picture.
> So the question is: what is the purpose of the filter in modulate_vector_bc 
> <https://github.com/gnuradio/gnuradio/blob/master/gr-digital/lib/modulate_vector.cc> function?
> Is this a bug or is there a reason for this?
> Modulate vector question.png
> --
> BR,
>
> Marcin Puchlik____