Signal Source

Signal generator: generates a variety of waveforms.

Supports an output of type complex, float, int, and short

Parameters

(R): Run-time adjustable

Sample Rate (R)

Default value: samp_rate

Sample rate (fs) is the average number of samples obtained in one second. Its units are samples per second or hertz e.g. 48,000 sample rate is 48 kHz.

Waveform (R)

options: [Constant, Sine, Cosine, Square, Triangle, Saw Tooth]

Constant

A constant value as specified by Amplitude + Offset

Sine

Real-valued signal types: Amplitude·sin(2π·Frequency/Sample Rate·n) + Offset

Complex-valued signal types: Amplitude·[cos(2π·Frequency/Sample Rate·n) + 1j·sin(2π·Frequency/Sample Rate·n)] + Offset

Cos

Real-valued signal types: Amplitude·cos(2π·Frequency/Sample Rate·n) + Offset

Complex-valued signal types (identical to Sin): Amplitude·cos(2π·Frequency/Sample Rate·n) + 1j·sin(2π·Frequency/Sample Rate·n) + Offset

Square (Phase wraps in [–π,+π], increasing by Frequency/Sample Rate every sample)

Real-valued signal types:

phase < 0: Amplitude+Offset

phase ≥ 0: Offset

Complex-valued signal types (Real part: 0-centered π-wide square wave, Imag leads Real by 90°):

phase in [-π, -π/2): Amplitude + 0j + Offset

phase in [-π/2, 0): Amplitude + 1j·Amplitude + Offset

phase in [ 0, +π/2): 0 + 1j·Amplitude + Offset

phase in [+π/2, +π): 0 + 0j + Offset

Triangle (Phase wraps in [–π,+π], increasing by Frequency/Sample Rate every sample)

Real-valued signal types:

Phase in [-π, 0): Linear ramp from -Amplitude to +Amplitude (both + Offset)

Phase in [0, +π): Linear ramp from +Amplitude to -Amplitude (both + Offset)

Complex-valued signal types (Real part: triangle wave, rising in [-π,0), falling [0,+π), Imag leads Real by 90°):

phase in [-π, -π/2): TODO

phase in [-π/2, 0): TODO

phase in [ 0, +π/2): TODO

phase in [+π/2, +π): TODO

Sawtooth (Phase wraps in [–π,+π], increasing by Frequency/Sample Rate every sample)

Real-valued signal types (Rises from -π to +π, then jumps back to -π):

Amplitude·phase / (2π) + Amplitude/2 + Offset

Complex-valued signal types (TODO)

For selection with a variable, the following values should be used:

• Constant = analog.GR_CONST_WAVE
• Sine = analog.GR_SIN_WAVE
• Cosine = analog.GR_COS_WAVE
• Square = analog.GR_SQR_WAVE
• Triangle = analog.GR_TRI_WAVE
• Sawtooth = analog.GR_SAW_WAVE

Frequency (R)

Frequency of the waveform (default: 1000)

Amplitude (R)

Amplitude of the output (default: 1)

Offset (R)

Offset from zero (default: 0)

Initial Phase (Radians) (R)

Default: 0

Message Ports

cmd

The 'cmd' message port accepts message pairs.

• 'freq' . float value
• 'ampl' . float value
• 'phase' . float value
• 'offset' . float value

For GNU Radio 3.8, the messages dont work correctly with pairs, but they do work fine with a dictionary. This issue is explained here.

The amplitude of the signal source can be changed to 0.5 by adding the following PMT to the message strobe block.

 pmt.dict_add(pmt.make_dict(), pmt.intern("ampl"), pmt.from_double(0.5))

The above command creates a dictionary and adds a pmt pair of ("ampl", 0.5) to the dictionary.

freq

The value of frequency in the signal source can be changed by connecting a message strobe. The Message PMT parameter can be set to pmt.from_float(new_freq). In this way, the frequency of the signal source will be changed to new_freq value after the specified period in the message strobe.

The 'freq' message port has been deprecated in 3.9 in favor of the 'cmd' message port.

Example Flowgraph

This flowgraph is for version 3.9+.

Example Output

Types of Waveforms:

Cosine (complex):

Constant:

Square:

Triangle:

Sawtooth:

Source Files

C++ files

sig_source_impl.cc

Header files

sig_source_impl.h

Public header files

Base

Waveforms

Block definition

analog_sig_source_x.block.yml