[sdiy] passive ring modulator transformers

[Richie Burnett]

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