[sdiy] passive ring modulator transformers

[Richie Burnett]

Thanks Neil.  They are all pretty clear on the matter!  A diode ring 
modulator (double-balanced mixer) operates as a switching modulator, not a 
product modulator like I had always thought.  So it doesn't really matter 
what waveshape you feed into one of the inputs of a real diode ring 
modulator, as long as it has sufficient amplitude to commutate the diodes!

-Richie,

-----Original Message----- 
From: Neil Johnson
Sent: Sunday, January 17, 2016 8:04 PM
To: Richie Burnett
Cc: Simon Brouwer ; synthdiy diy
Subject: Re: [sdiy] passive ring modulator transformers

Hi Richie,

Here is some more light reading for you:

The original Cowan patent:
http://patft.uspto.gov/netacgi/nph-Parser?patentnumber=2025158

The wikipedia page:
https://en.wikipedia.org/wiki/Ring_modulator

My own take on things:
http://www.milton.arachsys.com/nj71/index.php?menu=2&submenu=2&subsubmenu=12

Cheers,
Neil


On 17 January 2016 at 19:50, Richie Burnett
<rburnett at richieburnett.co.uk> wrote:
> Fair enough :-) who am I to argue with minicircuits!!! I'm still not sure 
> whether that app note is actually saying that you *can* use a diode ring 
> mixer as a switching modulator if you have square waves conveniently 
> available instead of sines, or if they are saying that it *always* 
> operates in a switching mode regardless of the drive waveform. I guess 
> whether this mattersor not depends on what you're using it for.
>
> I've always thought of ring modulators as proportional devices. Albeit 
> ones that aren't particularly linear and distort a lot. And for the right 
> range of amplitudes in, you can get a decent approximation to a linear 
> multiplication function, as shown in the video you linked.
>
> It's interesting that they say pulse inputs actually reduce distortion 
> though! I know switching modulators are often used by the software defined 
> radio crowd so they obviously work fine that way.
>
> Cheers,
>
> -Richie,
>
> Sent from my Xperia SP on O2
>
> ---- Neil Johnson wrote ----
>
>>Hi Ritchie,
>>
>>> My point was that his two cases of a gain of +1 and -1 are just the 
>>> saturated gains.
>>
>>This Minicircuits document: https://www.minicircuits.com/app/AN00-011.pdf
>>would seem to disagree with you:
>>
>>Q. I am a digital designer, dealing with pulses rather than sine
>>waves. Is it necessary to
>>furnish only sine waves to a double-balanced mixer?
>>A.
>>No. A double-balanced mixer operates as a switching device; pulses are
>>fine, and may
>>even reduce distortion.
>>
>>> The diode mixer or ring modulator is a proportional device, and in fact 
>>> Minicircuits even recommend a sinusoidal local oscillator signal at 
>>> +7dBm level for optimum operation. With harder LO drive the behaviour is 
>>> less linear and tends more towards the saturated switching behaviour, 
>>> with the addition of a whole load more distortion products in the 
>>> output.
>>
>>The +7dBm (level 7 device) spec is to do with conversion gain or loss,
>>not about driving the diodes.  Other mixers are designed to be run at
>>higher levels, upto +27dBm for some devices (they tend to be rather
>>more esoteric!).
>>
>>> Yes, that dafx paper is the one I was thinking about. Thanks for the 
>>> links! I only skimmed over it but it looked good.
>>
>>Hmmm...
>>
>>Cheers,
>>Neil
>>--
>>http://www.njohnson.co.uk



-- 
--
http://www.njohnson.co.uk


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