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gnu radio - bit rate

I have propably very stupid/simple question to GnuRadio users.

I have a Random Source as a source of bits [-1, 1]. And I want to multiply every bit with cosinus to make bpsk modulator. Problem is that Bits are generated as fast as possible... (dont have enything in common with samp_rate). When I have 1 period of cosinus, there are generated many bits from Random Source.

Question is, how can I slow down bit rate generation ??

Thanks for any help enter image description here

(I dont want to use DPSK Mod :))

Solution

  • Strictly speaking you can not delay the generation of bits. However you can increase the duration of each symbol. This can be done with the repeat block of GNU Radio. This block takes a parameter called interpolation that corresponds to the number of times an input item will be repeated at the output.

    So you find the period of your cosine in samples, lets say p. For each random bit produced by the Random source block, you repeated it p times with the repeat block. With this way you increase the duration of your random symbol. Then you pass the resulting samples to the multiply block of your flowgraph.