Swamp Thing
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I was playing with a toy model ( HTML + JS ) involving a mass, spring and damping that lets you vary those parameters using sliders. In the process, I got interested in the idea of varying the stiffness in real time in order to demonstrate parametric amplification.
This does work pretty well when you vary the stiffness directly at twice the resonant freq, but then I decided to simulate something more like an actual RF / microwave parametric amp. I put in a nonlinear equation for the spring, and added a pump excitation and a signal excitation. The idea is that you don't vary the stiffness directly, but rather you apply a pump input that uses the nonlinearity to modulate the stiffness indirectly.
This version doesn't work as expected and I'm trying to debug it.
But I have this question: in order to work, is it necessary to apply the pump force directly to the spring (for example by pulling up and down on the supporting point)? At the moment I am applying the signal force as well as the pump force to the mass itself. I have begun to get a vague intuitive feeling that this is not the way it would work.
Any thoughts?
This does work pretty well when you vary the stiffness directly at twice the resonant freq, but then I decided to simulate something more like an actual RF / microwave parametric amp. I put in a nonlinear equation for the spring, and added a pump excitation and a signal excitation. The idea is that you don't vary the stiffness directly, but rather you apply a pump input that uses the nonlinearity to modulate the stiffness indirectly.
This version doesn't work as expected and I'm trying to debug it.
But I have this question: in order to work, is it necessary to apply the pump force directly to the spring (for example by pulling up and down on the supporting point)? At the moment I am applying the signal force as well as the pump force to the mass itself. I have begun to get a vague intuitive feeling that this is not the way it would work.
Any thoughts?