[time-nuts] Double balanced mixer question

[Attila Kinali]

On Fri, 24 Jul 2020 01:37:04 +0200
Attila Kinali <attila at kinali.ch> wrote:


> Due to a diode mixer not being a good multiplier (it only
> multiplies the signs and adds up the amplitudes... and has
> offset voltages when the switching happens) you will
> get quite strong second order components like 2*LO-RF.
> The only way to dampen them is to make the mixer as symmetric
> as possible or to use a push-pull kind of architecture to
> cancel out second order components (e.g., a double-double-balanced
> mixer)

Blub.. I should not write mails when I'm tired.... Let me correct this:
It would not be 2nd order components, but 3rd order components 3*LO-RF
and 2nd order harmonic (2*LO, 2*RF) leakage.

While the latter can be reduced by better symmetry, the former is
intrinsic in the working of the double balanced diode mixer. I don't
know of any way how to reduce that, but I am not a specialist in
mixer design, so that doesn't mean anything.

			Attila Kinali
-- 
Science is made up of so many things that appear obvious 
after they are explained. -- Pardot Kynes