Frequency Mod

This block is an input amplitude controlled complex sine. It outputs a signal, which has a momentary phase increase that is proportional to sensitivity and input amplitude.

More specifically, takes a real, baseband signal (x_m[n]) and output a frequency modulated signal (y[n]) according to:

Where x[n] is the input sample at time n and $f_{\Delta }$ is the frequency deviation. Common values for $f_{\Delta }$ are 5 kHz for narrowband FM channels such as for voice systems and 75 kHz for wideband FM, like audio broadcast FM stations. In this block, the input argument is sensitivity, not the frequency deviation. The sensitivity specifies how much the phase changes based on the new input sample. Given a maximum deviation $f_{\Delta }$, and sample rate $f_{s}$, the sensitivity is defined as:

Parameters

(R): Run-time adjustable

Sensitivity (R)

Sensitivity = (2 * math.pi * deviation) / sample_rate

where 'deviation' is the desired value for an input not exceeding [-1, 1]. If the input is outside [-1, 1] it can deviate more.

Example Flowgraph

Source Files

C++ files

frequency_modulator_fc_impl.cc

Header files

frequency_modulator_fc_impl.h

Public header files

frequency_modulator_fc.h

Block definition

analog_frequency_modulator_fc.block.yml