RadioBanter - View Single Post

March 14th 04, 12:35 AM

On 13 Mar 2004 19:00:19 GMT, (Avery Fineman)
wrote:

In a way, it IS. Fifth harmonic of an infinitely sharp transition
rectangular waveform is still low in energy compared to the
fundamental. Chances are that a single stage using an active
device as a quintupler will NOT be successful, transistor or tube
(valve).

I find that surprising but bow to your superior knowledge...

Let's get to some specifics on this problem -

1. Let us know what you are using to determine whether or not
a 5th harmonic exists. The lack of indication may be due to
whatever it is (not a spectrum analyzer) being used.

As I said, since I've disposed of my SA I have no way of detecting the
presence of the 5th unless it's strong enough to be seen by 'scope or
read by my frequency counter. (Except for your brilliant idea of using
an HF rx, that is, which I intend to implement 2morrow).

2. Describe the multiplier stage in more detail and include an
approximate level and impedance/admittance of the RF
source. That would include supply rails and biasing.

There's a circuit diagram now viewable on abse under a similar thread
title. That should answer all your queries...

3. Describe whatever is being used to select the 5th harmonic
and inhibit the fundamental and other harmonics. There's
lots of energy at many different frequencies floating around
there and you only want one frequency.

Nothing more than what you can see in the schematic's two stages.

4. Review again with us the output drive level requirements so
we can get a handle on that.

It's got to eventually end up feeding another CMOS inverter for a
tripler stage.

5. If you are using an oscilloscope to measure the fundamental
waveform, estimate the actual risetime/falltime based on the
rise/fall times limits of the oscilloscope. That yields some
basic data that can be applied to a Fourier series to determine
the level of 5th harmonic energy you have to work with. [that
will also reveal the approximate frequency limits of the scope]

I prefer to go by the device's datasheet. In this case, the r/f times
are 7 to 8nS.

If there's anything I've missed out, lemme know...

--

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