[time-nuts] Hetrodyning concept

[Bob kb8tq]

Hi

If you feed two identical signals into a double balanced mixer, 
you get 2X the input frequency and a DC component as the “ideal”
outputs. You also have the input feed through and N x the input 
bouncing around as “non-ideal” signals. ( = the full expansion has 
a *lot* of terms in it). 

A normal ( = saturated inputs) diode ring double balanced mixer has 
a non-linear transfer function for the DC output. As you shift phase, an ideal 
mixer would have a sine wave voltage vs phase plot. A saturated mixer 
has something that looks more like a clipped triangle wave as it’s plot. 

So, simple answer is that single double balanced mixer does not do
a very good job as a wide range phase detector. It’s great for phase
noise (when properly set up), but not ideal for an unlocked system.

Bob

> On Apr 27, 2020, at 4:08 AM, Taka Kamiya via time-nuts <time-nuts at lists.febo.com> wrote:
> 
> I have a question on heterodyining concept.
> Say you have f1 and f2.  Say you have f1 <> f2.  Then the product is |f1+f2| and |f1-f2|.  (fundamental is not considered here)
> What would happen f1 = f2?  If phase is the same, it will be 2sin(omega t).  (amplitude doubles)  If phase is an odd multiple of pi radian different, result is zero.  (cancels out each other)
> What I am trying to do is to first, understand this in case where f1 = f2, and second, mix f1 and f2 and get f3, which is a sum of f1 and f2.  Doubling won't do.
> Can someone help me understand this?  I haven't seen discussion of cases where source frequencies are equal anywhere.
> 
> 
> 
> --------------------------------------- 
> (Mr.) Taka Kamiya
> KB4EMF / ex JF2DKG
> _______________________________________________
> time-nuts mailing list -- time-nuts at lists.febo.com
> To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.