A simple way to look at this is if the non-linearities/distortion are
_symmetrical_ on both the positive and negative sides of the AC waveform
only odd harmonics are generated. All other cases produce both even and
odd harmonics. The most fundamental example is a square wave (50% duty
cycle) which only has odd harmonics. Any other duty cycle has both even
and odd harmonics. There are some odd (not generally occurring in
circuits) cases where the above is not true but they only detract from
the basic cases.
IMD on the other hand is produced by ANY non-linearity.
The harmonics are easy to demonstrate with the free program LTSpice
(www.analog.com). If anyone wants a LTSpice file showing this I can
provide it.
Larry, W0QE
On 12/27/2011 9:59 AM, chas wrote:
> On 12/25/11 9:01 AM, Fuqua, Bill L wrote:
>> You can have IMD without any second harmonic. All you need is the third
>> order polynomial term of the Vout/Vin curve. Simply have two Cosines of
>> different frequency, summed together raised to the power of 3 you get
>> fundamental, third harmonic and the IMD products we see with a two tone
>> test. I sent out a paper on IMD and Cross cross modulation some years ago
>> to this group. On vacation now and don't have it on this computer. Maybe
>> one of you can locate it. All the math is there. No rocket science. Just
>> some algebra and trig. Peaking the plate tune cap last for max output does
>> not mean that you have matched impedance. It just makes the net result
>> resistive and not reactive. That is to say Resonant. Rather than off
>> resonance. 73 Bill wa4lav _______________________________________________
>> Amps mailing list Amps@contesting.com
>> http://lists.contesting.com/mailman/listinfo/amps
>
> As much as I hate to admit it but allowing for the fact that this list is not
> made up of Lawrence Livermore employees, professional mathematicians, etc
> I will hazard a guess that I am in the vast majority when I have to ask "what
> in 'ell did you just say?".
>
> In other words, feel free to talk down to the rest of us whose PhDs, MDs, etc
> are not in your field of - math above Jr High Algebra...<G>
>
> I realize that you might find it impossible to detune your Einstein level
> math speech but perhaps you could give us a band graph showing what we should
> be doing instead of expecting us to move into your head and to pick up the
> math computations which you are using.
>
> thanks
> chas k5dam
> Houston, Tx
>
>
>
>
> Chas
>
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