clipped sinewave

In the TCXO spec, the output is a clipped sinewave. The form of the clipped sinewave I measured by oscillograph is very weird. So who can give me a reference about the clipped sinewave?

clipped sinewave is a sin wave that contains some harmonics....for example when an opamp work in saturation and its input is a sin wave....then it's output is a clipped sinwave.

http://www.dliengineering.com/vibman...eirspectra.htm