Some phasemodulation thoughts

[Magnus Danielson]

From: Rene Schmitz <uzs159 at uni-bonn.de>
Subject: Re: Some phasemodulation thoughts
Date: Wed, 06 Oct 1999 16:58:03 +0200

> 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.)

No, it would not. It is the half-wave property you should be looking for.

You must understand that the whole cursuit is a very quick-and-dirty solution
with numerous of "problems".

> >> 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.... ;->)

You mean 100mF 1% MKT...

It is very important to have balanced light conditions. Personally I don't
accept headligth bulbs which are not matched tighter than +/- 1 ppm relative
each other. (Says the man without a car)

> 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 ;-)

Yeah, I know... sorry. I know these things break the image of me as being an
analogue genious, wizard, god whatever, but it is better that I swear about
some minor technial misstake that nobody cared to find than somebody come up
with it, this just improves on the status scale ;)

Oh, did I still have the thread on the list?? ;) ;)

Cheers,
Magnus (who foul up all the time, but covers it quickly so no one will discover)