Re: Frequency Halver

From: Robert Baer (robertbaer_at_earthlink.net)
Date: 03/21/05 

Date: Mon, 21 Mar 2005 06:25:25 GMT

bill.sloman@ieee.org wrote:

> Robert Baer wrote:
>
>>bill.sloman@ieee.org wrote:
>>
>>
>>>Sorry John, but I think you have just described a frequency
>
> doubler,
>
>>>rather than a frequency halver.
>>>
>>>For what it is worth, I'm pretty sure that there is no analog
>
> technique
>
>>>that will halve the frequency of a sine wave. It is easy enough to
>
> use
>
>>>a largely digital circuit to produce a sine wave which follows half
>
> the
>
>>>average frequency of of an analogue sine wave, and if you got
>
> really
>
>>>cute, you could track the phase of the input sine wave and produce
>
> an
>
>>>output whose phase varied at half the rate - though since the
>
> maxima
>
>>>and minima of a sine wave don't tell you much about the
>
> instantaneous
>
>>>phase, this isn't going to be perfect either.
>>>
>>>---------
>>>Bill Sloman, Nijmegen
>>>
>>
>> Incorrect; over 40 years ago we did that at Sylvania with a
>
> tetrode.
>
>> See a previous response by me earlier in this thread.
>
>
> You didn't halve the frequency of a sine wave, you used the input
> frequency to excite a tuned circuit that was resonant at roughly half
> the frequency of the input circuit, a much less direct relationship.
>
> ----------
> Bill Sloman, Nijmegen
>
   Correct, but the result is essentially the same.
   And it will track frequency changes, apparently up to 10% and perhaps
allows AM to pass thru as well (this last part i do not remember; been
too long).