Re: Understanding Pulsed signal Demodulation and decimation in GNU Radio

[Fabian Schwartau]

Hi Isaac,

I am not sure what you are trying to achive. However, your low pass 
filter seems to be set up incorrectly. You have a signal with 1MHz and 
10MHz samplerate. Your low-pass filter has a cutoff at 5MHz and then 
down-samples by 100. If you want to make sure that there are no 
frequency components aliased during the downsampling step, you should 
have a cutoff of 100kHz or below. When you set the cutoff to 100k and 
the transition width to 50k, you get a nice constant rect at the output.

Hope that helps.
Best,
Fabian

Am 20.07.22 um 19:03 schrieb isaac mario tupac davila:
> Hello everyone
>
> My name is Isaac. I'm dealing with a curious behaviour that I can't 
> understand...
>
> I'm generating my pulsed signal by multiplying a vector source and a 
> signal source. Then I'm multiplying this pulsed signal with a continuous 
> signal source at the same frequency, passing then for a low pass filter 
> and seeing it in a time sink block.
>
> The result should be a set of rectangles with the same amplitude and 
> period. The curious thing here is that the amplitude varies in time 
> (from 0 to max amplitude and vice versa). Any idea why the amplitude 
> varies in time?
>
> I attach the flowgraph just in case.
>
> Any idea or help will be appreciated.
> Thanks
> Isaac t.