[sdiy] Hopf bifurcation VCOs

[Ian Fritz]

At 02:51 PM 11/10/05, yves usson wrote:
>Looks promising...

Yves --

Yes, indeed.  What are the other options?  You can generate quadrature 
signals from a standard tri oscillator and then shape them.  But this takes 
a bit of circuitry and it is hard to get the distortion as low as what I 
get (if you really care about that).  Or you can make a 4-pole filter 
oscillate, but that's a more complicated fourth order system and the 
signals are distorted by the severe clipping that is needed to stabilize 
the loop. W. Jung gave a simple circuit (ENotes App. Note 29) but it uses a 
double integrator and it is not obvious how to modify it for VC operation.

Anyone have other favorite sinusoidal quadrature oscillators?

   Ian