Sine-fit procedure for unevenly sampled, multiply clocked signals

When signals are unevenly sampled and homodyne or heterodyne setups are used that involve multiple clocks, it is not possible to use the standard algorithms to produce accurate spectral density estimates. The PVLAS experiment is an example of such an experimental scheme and here it is shown how to implement an algorithm which generalizes the standard sine-fit and Lomb–Scargle procedures to obtain both amplitude and phase of important Fourier components of the physical signal, with an application to PVLAS data.