Re: [Discuss-gnuradio] Frequency modulation in GRC

[Activecat]

On Mon, May 26, 2014 at 10:20 AM, Activecat <address@hidden> wrote:

On 25.05.2014 20:01, jason sam wrote:

> But if it is doing FM then there should be some min and max
> frequencies between which the signal will be switching?

If you refer to the source code of the frequency_modulator_fc_impl.cc, then the min and max frequencies could be calculated.

Says, your sampling rate is samp_rate

Assuming the lowest input value to the FM block is zero, then
  minimum frequency of the FM output = samp_rate * sensitivity / ( 2 * PI )

Assuming the highest input value to the FM block is Vmax, then

  maximum frequency of the FM output = samp_rate * ( sensitivity + Vmax ) / ( 2 * PI)

To avoid disagreement, the sampling rate (samp_rate) refers to the number of elements produced by this FM block per second.

If there is no speed-limiting element (throttle, usrp, sound card etc) in the flowgraph, then someone may say that samp_rate becomes meaningless, if this is the case then in fact frequency also becomes quite meaningless..