tri lfo with 90deg lag?(blush)

[jhaible]

> Look up the Harald Bode patent "Multiphase Signal oscillator" US patent
> no. 4,145,670 dated March 20, 1979. This describes a sin-cos quadrature
> oscillator using 2 allpass sections, apparently  being well suited for
> frequency shifter applications. An implementation using OTA's is shown.
>

Haven't seen the patent yet. But in his FS, he uses a quadrature BFO,
i.e. ordinary VCO (no quadrature), plus fixed frequency oscillator and
(fixed frequency) 90 degree phase shifter, plus 2 ring modulators.

Works, but is much too complicated IMO.

JH.