Signal Generator - portapack-mayhem/mayhem-firmware GitHub Wiki

The signal generator found under Utilities can be used to generate a carrier which can be FM modulated with the following waveforms as defined by the Shape function.

• CW : unmodulated carrier
• Sine signal
• triangle signal
• sawtooth up signal
• sawtooth down signal
• square signal
• noise signal

* Sine / Triangle / Sawtooth up / Sawtooth down / Square

We can select the periodic signal to modulate the carrier , in FM .(and we can adjust below the delta FM deviation)

Tone defines the frequency of modulation.

Update when unchecked requires the user to drop carrier, then re-start carrier in order for a change of modulation Shape or Tone frequency to take effect. When checked, values will update on the fly.

Stop after 1s limits carrier duration to 1 second

* White Noise generator options:

We are generating simulated White Noise ,using pseudo random noise generator, 8 bits linear-feedback shift register (LFSR) algorithm, variant Fibonacci. (Following this wiki link)

Example of the implementation of a 8 bite Noise option

We have introduced only one user option, about Noise generator , using the best LFSR that we tested : 16 bit polynomial feedback LFSR , that has longer random sequence period and produces more continuous spectrum.Using noise generator, we can hear in any FM receiver the random noise (and we can also see the random demodulated signal, as it is attached below ) and the peak radiated spectrum power is now just -10 dB's compared to the triangle or saw signal , that is fine (acceptable) . (not -40 or -50 dB's as it was before, really too small) .

See on top right corner the pseudo random noise demodulated sinal

Update when unchecked requires the user to drop carrier, then re-start carrier in order for a change of modulation Shape or Tone frequency to take effect. When checked, values will update on the fly.

Stop after 1s limits carrier duration to 1 second