[sdiy] Re: Saw phase shifter used in frequence shifting.

[Magnus Danielson]

From: karl dalen <dalenkarl at yahoo.se>
Subject: Saw phase shifter used in frequence shifting.
Date: Sat, 17 Sep 2005 03:29:25 +0200 (CEST)
Message-ID: <20050917012925.6623.qmail at web25502.mail.ukl.yahoo.com>

> Harry, Magnus and the rest who migh be interested!
> 
> I came onto a idea here, can it be so that one could 
> use the phased saw as a angle wrecker for an frequency shifter?
> SSB, DSB type of shifter? (asuming the saw goes to the basic
> saw to tri and then diode or saturated OTA sine shaper).
> 
> If a PW width of 50 declare 0 degres (saw phase will then start
> at 90deg and end at 270 so the variable range would be 180 deg)
> and anything above 50 gives positive direction of frequency 
> shifts and anything below 50 gives negative frequency shift?
> 
> You still have the straight saw available as phase reference
> 
> Many types of quadratues could easily
> be made out from one saw phase VCO!
> 
> Bad idea?

No, I don't see any problem with this. It should work well to get the quadrant
variant from the same oscillator core. What is an issue, is the overtones of
the shaped sine which I think is more of a concern for a frequency shifter than
for normal musical useage. However, beyond that I can't see any problem.

So, for the carrier oscillator it is clearly a go, the phase-shifting network
for the signal remains an issue, but the polyphase filter is fairly simple and
should work well.

Go for it! ;O)

Cheers,
Magnus