Based on https://en.wikipedia.org/wiki/Phase-locked_loop and ported directly from the C code as per https://liquidsdr.org/blog/pll-howto/
Can lock onto reference signal even when frequency is allowed to vary randomly (noisy), e.g.:
cargo run -- --ref.varyRandomChance=0.9 --ref.varyRandomMax=0.1 --ref.frequency 0.2 --samples 400 --pll.bandwidth 0.02 > pll_example.dat && gnuplot -e 'set terminal png size 800,700' pll_example.gnuplot > pll_example.png
...produces output like:
When the input/reference frequency (--ref.frequency) is increased, it helps to increase the bandwidth (--pll.bandwidth) of the output/signal accordingly, or it will take very long to achieve lock (if at all!).
A similar effect can be achieved by increasing the damping factor (--ref.damping) - possibly because this allows the output oscillator to change frequency more quickly, at the risk of introducing more noise.
If needed, install gnuplot first, e.g.
brew install gnuplot
Run the demo and output to dat file:
cargo run > pll_example.dat
Output the plot using gnuplot:
gnuplot -e 'set terminal png size 800,700' pll_example.gnuplot > pll_example.png
- Simulate varying frequency
- Automatic peak detection from noisy ref?