[time-nuts] DMTD - analog multiplier vs. diode mixer ?

Li Ang lllaaa at gmail.com
Fri Jan 8 21:19:05 EST 2016


Hi Bob,
    In some article, I see people use a D-flipflop to sample the input
signal with reference clock. When you want implement a mixer what's the
difference between D-flipflop and XOR gate? Acorrding to my understanding,
to multiply 1bit with another, I should use an AND gate, right?
    When you refer high speed CMOS XOR gate, do you mean 74LVC1G86?

Thanks

BI7LNQ


2016-01-09 6:42 GMT+08:00 Bob Camp <kb8tq at n1k.org>:

> Hi
>
> The board I have uses high speed CMOS single gate XOR’s. They have a
> pretty good
> phase noise floor (-170’s) so they should be pretty reasonable.
>
> Bob
>
> > On Jan 8, 2016, at 12:16 PM, Richard (Rick) Karlquist <
> richard at karlquist.com> wrote:
> >
> >
> >
> > On 1/7/2016 3:11 PM, Bob Camp wrote:
> >> Hi
> >>
> >> If your intention is to run a mixer with saturated inputs …. just run
> >> an X-OR gate. It will handle the high level signals much better than
> >> an over-driven analog part.
> >
> >> Bob
> >>
> >
> > If you look at the schematic of an XOR gate IC and compare it
> > to the schematic of, for example, an MC1496 mixer, you will
> > see a lot of similarity.  If the gate is of the ECL type,
> > it will have the addition of emitter followers, but that
> > it a minor detail of implementation.  I'm not sure there
> > is a huge difference.  ECL is a great logic family in
> > general (self-confessed ECL-phile here :-) but it is
> > probably the worst for phase noise, compared to the
> > saturating logic types.
> >
> > Rick Karlquist N6RK
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