More than one frequency appearing in a circuit?

[hobbs125]

If a circuit is oscillated at one frequency what basic components (resistors, capacitors, inductors) or configurations of components can cause other frequencies to appear?

[f95toli]

None of the above, in order for more frequencies to be generated (usually harmonics) you need some non-linear component in the circuit; such as a diode.

[hobbs125]

Ok, can you explain how it happens? I've been trying to understand but I don't quite get it?

[skeptic2]

What kinds of other frequencies are you seeing. Are they harmonics of the fundamental or are they unrelated to the fundamental.

Both capacitors and inductors may create additional resonances and cause oscillation on more than one frequency at the same time. I've accidentally done that.

[hobbs125]

I think that may be what's happening. I've got a circuit which consists of a transformer with three secondary coils connected in series. The transformer is pulsed with a square wave. Each secondary coil has a capacitance in parallel which is the coils capacitance. The circuit is oscillated so the secondary coils are at resonance to limit current. Two of The coils have a diode between them which is forward biased during the on time.

The circuits purpose is to charge a capacitor to a high voltage while limiting current.

I'm actually getting an am waveform across the coils which leads me to believe the frequencies are close.
What I'm not understanding though is how it's occurring.