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From: "Alfred Lorona"
Subject: Re: How does a mixer work?
Date: Wed, 16 Oct 2002 21:22:52 -0700
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"Asa Cannell" wrote in message
> How does a mixer work? I don't understand why it needs a non-linear
> element. I think examples of why a linear element (resistor) wont work
> would help illustrate why a non-linear element (diode) will. Also,
> what does 'mutiply' mean in terms of mixing? What if two DC signals
> are applied to a mixer, like 2V and 4V? Will the output be 8V?
If you apply a 10 hertz and a 15 hertz signal to a resistor all you can
expect as output is a 10 hertz signal and a 15 hertz signal. In a mixer, the
idea is to obtain the difference between the two frequencies which is 5
hertz and the sum of the two frequencies which is 25 hertz at the output.
The output will also contain the two original frequencies of 10 and 15
hertz. The useful, or desired, output signal is either the sum or the
difference frequency. All of the others are filtered out and only the
desired frequency is allowed to pass through to the rest of the circuitry.
You can only obtain the sum and difference frequencies in a non linear
circuit element. That is why a resistor, being a linear circuit element,
won't do the job.
The correct technical term for the mixing process in a mixer is called
'multiplication' but this sometimes confuses people such as you indicate
with your example of the two DC voltages. Hi.
Until you gain a more detailed idea of the mixing process, it may help to
just think of a mixer as a 'distorting' device that generates frequencies at
the output that are not present at the input . This is what distorting
A diode is a non linear circuit element and that is why it makes a good
mixer and is widely used in inexpensive AM radios.
No, mixers do not work with DC input signals.
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