[Amps] Subharmonic

[Michael Tope]

Tom,

Yes, it would seem a bit improbable for a system like this
to just happen by accident, although as the IEEE paper
points out, it is theoretically possible, which was, in and
of itself, news to me.

Whether you believe its due to parametric division, super-
harmonic injection locking, or some other less esoteric
mechanism (like a D flip-flop), the tracking relationship
between the 14 MHz fundamental and the 21 MHz
spurious suggests that an F/2 component is coming from
something (either in the transmitter or receiver).

David, please let us know what you find out with regard
to the 3F/2 mystery. I am really curious to understand
what is causing it.

73 de Mike, W4EF...........................................

----- Original Message -----
From: "Tom Rauch" <w8ji@contesting.com>
To: <amps@contesting.com>
Cc: "Michael Tope" <W4EF@dellroy.com>; "David Robbins" <k1ttt@arrl.net>
Sent: Tuesday, May 21, 2002 3:05 PM
Subject: [Amps] Subharmonic


> > The following is a link to an IEEE paper that I found this morning
> > which talks about (and references) analog frequency dividers.
> > Apparently the application is high frequency (microwave) low power
> > systems where digital dividers are not practical:
>
> Specially designed systems that have oscillators phase-locked to f/2
> are not very common accidents Mike. They take a lot of effort to get
> working and special components. I'm not even sure they are practical
> at HF.
>
> The most important point is conventional amplifier systems, or non-
> linear systems like unintentional diode junctions, can not generate
> subharmonics. For example, a conventional transistor operates in a
> low-Q low-impedance system **without** the required low-capacitance
> low-loss high-Q resonant f/2 resonant circuit to pump. Even if you
> had those components, it is very unlikely (probably impossible) to
> pump the circuit with a conventional semiconductor device used in
> PA's.
>
> If you read the text of the paper you pointed out carefully you will
> see the author dismisses the parametric divider as being difficult to
> implement, and requiring Hi-Q components that "can not be implemented
> in contemporary silicon technologies". He moves on to better
> concepts.
>
> I wouldn't worry much about seeing one pop up by accident, since they
> are very difficult to intentionally construct.73, Tom W8JI
> W8JI@contesting.com
>
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