Some phasemodulation thoughts

[Rene Schmitz]

At 00:05 06.10.99 +0200, Magnus Danielson wrote:
>The rectifier part is a quickie. It's not a precision rectifier or anything.
>One should probably be well of using just a few resistors more or something.

The active fullwave rectifier from Art Of Electronics 
(2nd ed p.222 fig.4.46 ) would fit nicely. I proposed the 1 transistor
rectifier to simplify it somewhat. Although I'm not not overly convinced of
this circuit. (For inputs near zero there is still the Vce(sat) at the
output.)

>> The ammount of hardware necessary for modulation indices of 10 and up would
>> be immense (without the AD/DA).  It could be relaxed somewhat if one uses a
>> sine generator which can go wider than 360 degrees. With a circuit that
>> does +/-540 degrees the count of rectifiers can be cut into half. The AD639
>> can do that. (Although it will be less precise then.)

>What? Don't you build PERFECT curcuits? ;)

(Well, normally I do: You should see the 100000uF 1% MKT array I use to
stabilize the voltage for my car stereo. And the matched pairs of
lightbulbs, for the headlights.... ;->)
 
Were talking about precision of 0.02% within the 500 degrees range, perhaps
a bit less in the next 40 degrees, and we have a glitchy sawtooth. Still
greater sine accuracy than a OTA as shaper.

>Depends on the design. There is nothing fundamentally diffrent, just that
>I bit my finger as i described that my method was in a way wrong. In
intention
>is was right.

Shh, I don't tell anyone ;-)

Bye
 René


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