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From: "Richard Hosking"
References: <email@example.com> <firstname.lastname@example.org>
Subject: Re: Polyphase network loss
Date: Wed, 11 Sep 2002 20:13:51 +0800
X-Newsreader: Microsoft Outlook Express 5.50.4133.2400
This network is capable of very good phase accuracy over a wide range (I
could get better than 30:1 freq range with 60 dB opposite sideband
suppression using enough poles)
As you say you trade this for loss inband though I found previously that out
of band losses were not nearly so great which presented a problem for
The problem is that there are 4 paths which need preamps from the Tayloe
mixer to the network.
Also I would like to avoid dual power supplies and have +12 V only with low
I tried to model it on my old version of Microcap (3!!)
but it wouldnt allow enough nodes - I have the free student version
Do you have pointers to a cheap/free simulator which could model a 6-8 pole
network? This would be about 36 nodes.
"Tom Bruhns" wrote in message
> I think you will find that in a passive network, you will end up
> trading phase match accuracy for gain (less loss). That's easy to see
> if you realize that the pole and zero positions determine the phase
> _and_ the amplitude versus frequency, and there is some minimum
> attenuation at DC. Since it's signal to noise ratio that you
> typically want to maximize, you may do better to optimize the source
> impedance to the following stage for noise, and not try to necessarily
> match impedance. In any event, I'd expect by the time you get to the
> receiver detected audio that your bandwidth would be limited enough
> that you could use a high dynamic range preamp before the phasing
> network and eliminate it as a SNR problem. (If you can afford the
> power, an OPA627 or AD797, depending on source impedance level, can
> give you really good spurious-free dynamic range for audio-range
> I'd also toss the network into Spice to get more understanding...there
> are multiple free spice programs out there.
> "Richard Hosking" wrote in
> > Dear all
> > I am interested in using a polyphase network as a 90 degree audio phase
> > shifter in a bilateral SSB system for QRP. The other components in the
> > generator path would be a Tayloe Mixer at input/ouput converting to an
> > switch to changeover from transmit/receive
> > One of the problems with using the polyphase network was inband loss. I
> > see a post recently claiming that his was minimzed by matching the
> > impedance wise.
> > Does anyone have any info on losses in these networks and how to minimze
> > them?
> > Richard
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