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

[Magnus Danielson]

From: karl dalen <dalenkarl at yahoo.se>
Subject: SV: [sdiy] Re: SV: Re: Saw phase shifter used in frequence shifting.
Date: Sat, 17 Sep 2005 23:29:23 +0200 (CEST)
Message-ID: <20050917212923.71842.qmail at web25508.mail.ukl.yahoo.com>

> 
> --- Magnus Danielson <cfmd at bredband.net> skrev:
> 
> > > I was talking about the SSB DSB shifters, dont they use just a simple
> > > LPF filter between each multiplyer! Maybe the allpass type sound better 
> > > then the SSB? I have no idea since i have never built a Frequency shifter
> > unit!
> > 
> > Sorry, I don't have all the frequency shifter layouts in clear memory, so you
> > can't expect me to have all the details, pros and cons directly available,
> > now
> > can you?
> 
> No not at all, offcourse i havent requested you to know everything,
> just interpreted  what you said as if using "allpass stage type " of shifter.

Well, most frequency shifters do use them and only when you made the comment
that they had lowpass filters I came to recall that type too, which I read
about in the PhD thesis. It was creeping way back in my memory it seems.

> > What is a common problem however, is the 90-degree angle of the oscillators,
> > since that will affect the mirror-cancelation which makes it become more than
> > a  expensive form of a ringmodulator.
> 
> > I have Mike Gingells PhD report online at
> > http://rubidium.dyndns.org/~magnus/synths/friends/gingell/
> > and in there you also find a review of different SSB techniques and their
> > pros
> > and cons. Highly recommened.
> 
> Will have a peek at that!

Please do. The interesing point is that the goal of the design is to lower the
other mirror image rather than to reach the 90 degree goal, which it does BTW.
Also interesting is that it is a fairly stable design and easy enought to use.

There are some interesting ideas about how to do quadrant oscillators too,
basically using the polyphase shifting network in the feedback chain.

Cheers,
Magnus