Re: Missing Positive Spectrum

[Paul Boven]

Hi Jay,

On 2/12/21 12:08 AM, Jay Patel wrote:
> I am trying to create an OFDM transmitter using GNU Radio Companion and 
> an Analog Devices ADALM-Pluto SDR (attached my *grc file). It looks like 
> i am missing something. When i visualize my spectrum, it only have 
> negative side, I am expecting both side of spectrum (something like 
> attached).

The problem seems to be with your 'Occupied Carriers'. This should be a 
vector of vectors of indexes, so I'm assuming that it should be 
integers, whereas arange gives you floats.

Try: [list(range(-15, 0)) + list(range(1, 16))]

This results in a symmetric spectrum.

Likewise, the format of the Pilot Carriers should be as a vector of 
vector of integers: [[-(ncarrier+1),(ncarrier+1)]]

Note that this puts the pilot carriers quite far away from your main 
signal, you may want to use some form of ncarrier//2 there. To actually 
see the carrier, use a symbol like [[1,1]] so that there's actually some 
energy in them.

The documentation of the block uses () whereas in Python, you need [] to 
create a vector.

Disclaimer: I know very little about how OFDM works, but this should 
help you make some progress.

Regards, Paul Boven.