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]; Description: see "Waveform Types" below

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

Waveform Types

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

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.