GRC - converting complex stream to vector for FFT

GNU Radio
1

I have complex multiplied a couple of 1 msps complex values and I wish
to do a 2048 FFT so am trying to convert to 2048-length vector but I
cannot find a suitable block in the ‘stream conversion’ group of GRC. By
making vec length 2048 I get the correct kind of connector on the output
of the block (dark blue) but the input is also dark blue and I just want
complex (Re, Im) alternating.

   Can someone point me in the right direction?

         Kind Regards,


                      John
2

On 06/02/2012 01:00 AM, John Shields wrote:

I have complex multiplied a couple of 1 msps complex values and I wish
to do a 2048 FFT so am trying to convert to 2048-length vector but I
cannot find a suitable block in the ‘stream conversion’ group of GRC. By
making vec length 2048 I get the correct kind of connector on the output
of the block (dark blue) but the input is also dark blue and I just want
complex (Re, Im) alternating.

  Can someone point me in the right direction?

I think you are looking for the stream to vector block? It will turn a
stream of X into a vector of type X, which you can pass into a FFT
block.

-josh

3

Thanks, Josh. Will give it a whirl.

        Kind Regards,

                  John
4

Hi Josh,
It turns out I was using the block I think you were
recommending. Here is a picture of the flowgraph with the red arrow
which would appear to be an issue as, with it present, the flow graph
will not execute.

         Kind Regards,

                 John
5

On 06/05/2012 11:38 PM, John Shields wrote:

Hi Josh,
It turns out I was using the block I think you were recommending. Here is a
picture of the flowgraph with the red arrow which would appear to be an issue
as, with it present, the flow graph will not execute.

vec length should be 1, thats referring to the input size.

set num items to be the fft length

6

On 06/06/12 18:40, Josh B. wrote:

Kind Regards,

John
Sorry Josh - had it backwards. When reversed, as you suggest, it works
like charm.

      Thanks very much,

             Slainte,

                   John