# Why are patterns repeated in the frequency-power graph of a periodic signal?

The original question was posted here.

I have a signal, which I'd like to treat as a non-continuous function now, let it be $$signal(t)$$. It looks like this:

Zoomed in a bit:

I create a Lomb-Scargle Periodogram using $$signal(t)$$, which I understand to be very similar to non-uniform FFT (that is to say, the $$t$$s for which $$signal(t)$$ is defined, are not always separated by equal distance - as it is the case now).

The computed plot, frequency vs power:

I am happy with the large peak on the left side of the plot, but I am confused about the peaks centered around 48. Zoomed in on those:

They seem to be a reflection of the peaks on the left. I suspect that it is something to do with the Nyquist frequency. The difference between largest and smallest $$t$$ is around $$27.8$$, and I have around $$1280$$ values of $$t$$ (nearly but not exactly equidistance from each other), so the sampling rate is $$1280/27.8 \approx 46$$. This is closed to the previously observed $$48$$, but also clearly distinct from it (ie the previously observed 48 was an approximation, not an exact value, but it was definitely not $$46$$).

How can I explain this peculiarity of the frequency-power plot of this function?