If you want to see individual carriers, you have to use a high
resolution FFT. Here's a 262144 point FFT on a DVB-T2 OFDM signal with a
1K FFT (853 active carriers). The carriers are spaced about 9 kHz.
Stronger tones are pilots.
https://twitter.com/drmpeg/status/670769195160858624
Ron
On 01/03/2016 04:34 PM, Aditya Virmani wrote:
Hello sir
Thank you for your reply. Well, I am trying to do some additional
operation to the receiver side of the OFDM transceiver (rx_OFDM).
I am intending to detect a doppler shift in the received signal, for
which I am trying to do an FFT over symbols collected in 1 second.
To test the case, I tried to do a large FFT over 4 same OFDM symbols,
which means a 4 x 64 FFT, which should give me 48 (corresponding to
occupied tones) peaks instead of a band.
The theory of peaks can be illustrated simply by the FFT theory. I can
share the reference for that if needed.
I hope I am clear here.
On Sun, Jan 3, 2016 at 7:06 PM, Martin Braun <martin.br...@ettus.com
<mailto:martin.br...@ettus.com>> wrote:
Typically, you'd do 1 (I)FFT per OFDM symbol. I recommend having a
look
at the tx_ofdm.grc and rx_ofdm.grc examples, which show a full
flow graph.
M
On 01/03/2016 01:22 PM, Aditya Virmani wrote:
> Hello everyone
>
> Iam trying to do run-time FFT over multiple OFDM symbols.
> For this, I feed in the same sequence of bytes for each OFDM symbol.
> As per my understanding, as I am feeding in the same sequence of
bytes,
> it should be generating same set of symbols, and then further if
we do
> FFT over multiple symbols which are same, we should get a
sequence of
> peak-and-zeros, instead of continuous FFT graph.
> This works fine if I do just with two symbols (screenshot of that
> attached), but when I feed in more than two, it results in error ( I
> think that the data doesn't reach the FFT block concurrently,
because
> the graph I get is same when I feed Null source and a Symbol
source to
> FFT).
>
> It would be great if someone can guide me with it.
>
>
> Regards
> Aditya Virmani
>
>
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