Freq. Independent Phase Shifter
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From: Bill Murphy on 11 May 2010 03:21 On Mon, 10 May 2010 18:24:52 -0700 (PDT), MooseFET <kensmith(a)rahul.net> wrote: >What are the two other channels making? > Same signal, all spearated by 120 degrees. Done in CoolEdit. >If you have two signals at 90 degrees, you can get any other phase >and the same amplitude. Can you give me a hint how, or where to find out please? Bill Murphy
From: Phil Allison on 11 May 2010 03:25 "Joerg" > > A Hilbert shifter works well, depends on the precision and how many > octaves you want. Also, you'd need to get hold of 0.5% or better film > capacitors which is not easy anymore these days. ** The use of 0.5% tolerance caps implies a phase ripple or error of better than 1 degree max. Using 1% tolerance or 1% values selected from 5% stock, the max phase error is not more than 2 degrees. There is no problem designing a Hilbert phase shift network that covers from 22 Hz to 20 kHz using only 10nF and 1nF polystyrene caps of nominal 1% tolerance, 1% MF resistors and a few FET op-amps. ..... Phil
From: Phil Allison on 11 May 2010 03:41 "Bill Murphy" > >>If you have two signals at 90 degrees, you can get any other phase >>and the same amplitude. > > Can you give me a hint how, or where to find out please? > ** Just by summing them in various ratios !! Call one " 0 " and the other " 90" - then summing equally gives 45 degrees relative to " 0" . Invert the " 0 " signal - then summing in various ratios with " 90 " gives all the angles between 90 and 180 degrees. Draw a phasor diagram and you will easily see it. ..... Phil
From: JosephKK on 11 May 2010 05:29 On Mon, 10 May 2010 21:17:03 GMT, billmurphy(a)protech.com (Bill Murphy) wrote: >On Mon, 10 May 2010 06:59:03 +0300, Paul Keinanen <keinanen(a)sci.fi> >wrote: > >>Since the OP only needed frequencies up to 2 kHz and was using COTS >>amplifiers, a cheap dedicated computer running a multiple (4-6) >>channel sound card running at 8-48 kHz sampling frequency would do the >>trick. >> > >What about a single card with 4.1 or 5.1 outputs? > >Either way, how would I generate the three 120 degree offset channels >in software? > >Thank you for your reply. > >Bill Murphy You should have said you wanted a tunable 3-phase supply (exciter).
From: Spehro Pefhany on 11 May 2010 06:56
On Tue, 11 May 2010 17:25:16 +1000, the renowned "Phil Allison" <phil_a(a)tpg.com.au> wrote: > >"Joerg" > >> >> A Hilbert shifter works well, depends on the precision and how many >> octaves you want. Also, you'd need to get hold of 0.5% or better film >> capacitors which is not easy anymore these days. > > >** The use of 0.5% tolerance caps implies a phase ripple or error of better >than 1 degree max. > >Using 1% tolerance or 1% values selected from 5% stock, the max phase error >is not more than 2 degrees. > >There is no problem designing a Hilbert phase shift network that covers from >22 Hz to 20 kHz using only 10nF and 1nF polystyrene caps of nominal 1% >tolerance, 1% MF resistors and a few FET op-amps. 0.1% resistors are cheap these days. Where can you buy PS caps of any tolerance ? NPO ceramic parts are available, but $$$$. Best regards, Spehro Pefhany -- "it's the network..." "The Journey is the reward" speff(a)interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com |