[sdiy] Re: linear FM

[Ian Fritz]

At 01:26 PM 2/5/2003, ASSI wrote:
>On Wednesday 05 February 2003 10:40, jhaible at debitel.net wrote:
> > Hmm, reversing the direction of current flow thru a capacitor doesn't
> > mean reversing frequency.
>
>A triangle oscillator can be viewed as a system that is based on
>integrating the frequency input to phase and then mapping the phase to
>amplitude in a linear-modulo-2pi fashion. Hence if you reverse the
>current flow, you reverse the sign of the variable being integrated,
>which is frequency.

The variable being integrated is current.  An electronic device cannot 
integrate a frequency.  This is nonsense.

And the correct amplitude variable for an oscillator with a cap being 
charged and discharges is not the current, but rather the charge or voltage.

>I hope you are familiar with the concept of a phasor as fear I can't
>explain it fully in a few lines (you probably have seen them in
>modulation diagrams). The length of that is the amplitude,
>the rotational speed of the phasor is frequency and angle the phase.
>One phasor is one sine component (cosine is just 90° away). If you add
>another phasor (harmonic component) you add it to the tip of the first.
>The resultant curve (somewhat resemblant of a cycloide) defines the
>phasor (addition of the two in vector fashion) for the combined
>waveform and in general can even have it's own frequency (harmonically
>related phasors will share a fundamental frequency).

I can assure you that you do not need to explain to us what phasors are.


   Ian