Re: [Discuss-gnuradio] Frequency modulation in GRC

[jason sam]

ok got it

On Mon, May 26, 2014 at 11:40 AM, Marcus Müller <address@hidden> wrote:

Hi Ali,

I'm talking about
http://gnuradio.org/doc/doxygen/classgr_1_1analog_1_1frequency__modulator__fc.html

This is the and thus only comprehensive documentation.
But really, all this block does is, like I in text [1] and activecat in
text and code[2] tried to explain,
is increase the phase of its output signal by sensitivity*input .
I get the feeling this has been discussed exceedingly enough, and would
like to close this thread.

Greetings,
Marcus

[1] It outputs a signal, which has a momentary phase increase that is

proportional to sensitivity and input amplitude

[2] d_phase = d_phase + d_sensitivity * in[i];

On 26.05.2014 06:25, jason sam wrote:
> Hi Marcus,
> I have seen the doxygen documentation but it's all  code there,no
> description.Can u kindly guide me where to find good documentations for the
> GRC blocks??
> Regards,
> Ali
>
>
> On Mon, May 26, 2014 at 7:31 AM, Activecat <address@hidden> wrote:
>
>> 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..
>>
>>
>>