Paul Burridge wrote in message . ..

What's a doubler based on the good old 1N4148 good for, top end
frequency-wise?

Thanks to Jan-Martin for his reference to some actual experiments.

But in reply to Paul, I'd ask: Do you understand how the "full-wave
rectifier doubler" works, basically? (Ideal waveforms and all that.)
Do you have a data sheet for the 1N4148? What items from the data
sheet do you suppose might limit the useful frequency? Can you make
an estimate, based on the data sheet numbers? What would you do in a
design to extend the frequency range for a given diode characteristic?
For example, what does diode capacitance do to circuit operation?
What does reverse recovery do? In the full-wave frequency doubler
circuit, what does the input impedance look like, assuming an ideal
transformer, when one diode is forward biased and the other is
reverse-recovering? Can you think of parts to add to cause that to
not be so much of a problem (assuming it is a problem)?

Thinking about this sort of thing is useful not only in figuring out
what to expect, at least ball-park, but also in getting better
performance out of someone else's circuit and/or understanding its
limitations.

Cheers,
Tom

On 22 Feb 2004 15:50:35 -0800, (Tom Bruhns) wrote:

But in reply to Paul, I'd ask: Do you understand how the "full-wave
rectifier doubler" works, basically? (Ideal waveforms and all that.)

IFAIA, pretty much the same as a full-wave rectifier in a PSU. All the
negative going half-cycles are converted to postitive going
half-cycles that 'slot in' between the unmodified positive half
cycles. The resulting waveform is twice the original frequency and
subsequent signal processing can restore this half-wave signal back to
a full sine wave of the desired output frequency.

Do you have a data sheet for the 1N4148?

I could get one off the good old 'net. Aw, **** it; I'll get one. Hang
on a minute..... Got it!

What items from the data
sheet do you suppose might limit the useful frequency?

Primarily junction capacitance, I guess. In this instance, 4pF.
There's also something called transit time, IIRC, which is relevant,
but for some reason it's not mentioned on the DS.

Can you make
an estimate, based on the data sheet numbers?

Nope. Maybe from the graphs, though...

What would you do in a
design to extend the frequency range for a given diode characteristic?
For example, what does diode capacitance do to circuit operation?

More slows it down.

What does reverse recovery do?

Slower recovery the same, I guess. I'm not totally familiar with this
parameter but it would make sense.

In the full-wave frequency doubler
circuit, what does the input impedance look like, assuming an ideal
transformer, when one diode is forward biased and the other is
reverse-recovering? Can you think of parts to add to cause that to
not be so much of a problem (assuming it is a problem)?

Totally beyond me at this stage, I'm afraid!

--

The BBC: Licensed at public expense to spread lies.

On 22 Feb 2004 15:50:35 -0800, (Tom Bruhns) wrote:

But in reply to Paul, I'd ask: Do you understand how the "full-wave
rectifier doubler" works, basically? (Ideal waveforms and all that.)

IFAIA, pretty much the same as a full-wave rectifier in a PSU. All the
negative going half-cycles are converted to postitive going
half-cycles that 'slot in' between the unmodified positive half
cycles. The resulting waveform is twice the original frequency and
subsequent signal processing can restore this half-wave signal back to
a full sine wave of the desired output frequency.

Do you have a data sheet for the 1N4148?

I could get one off the good old 'net. Aw, **** it; I'll get one. Hang
on a minute..... Got it!

What items from the data
sheet do you suppose might limit the useful frequency?

Primarily junction capacitance, I guess. In this instance, 4pF.
There's also something called transit time, IIRC, which is relevant,
but for some reason it's not mentioned on the DS.

Can you make
an estimate, based on the data sheet numbers?

Nope. Maybe from the graphs, though...

What would you do in a
design to extend the frequency range for a given diode characteristic?
For example, what does diode capacitance do to circuit operation?

More slows it down.

What does reverse recovery do?

Slower recovery the same, I guess. I'm not totally familiar with this
parameter but it would make sense.

In the full-wave frequency doubler
circuit, what does the input impedance look like, assuming an ideal
transformer, when one diode is forward biased and the other is
reverse-recovering? Can you think of parts to add to cause that to
not be so much of a problem (assuming it is a problem)?

Totally beyond me at this stage, I'm afraid!

--

The BBC: Licensed at public expense to spread lies.

On 22 Feb 2004 20:39:33 GMT, (Avery Fineman)
wrote:

Sorry. If you are using the passive diode doubler looking like a
full-wave rectifier circuit, and you have a symmetric square wave,
the only harmonics you get are from the transition edges.

Symmetric square waves have very low even harmonic energy
content; harmonics are in the odd harmonic frequencies.

A non-symmetric rectangular (not a 'square') waveform has more
even-harmonic energy content.

with some experience you might say something else. Even harmonics are
'harmonics' too

and for many purposes it is an advantage when the odd harmonic content
is low


----
Jan-Martin, LA8AK, N-4623 Kristiansand
http://home.online.no/~la8ak/

On 22 Feb 2004 20:39:33 GMT, (Avery Fineman)
wrote:

Sorry. If you are using the passive diode doubler looking like a
full-wave rectifier circuit, and you have a symmetric square wave,
the only harmonics you get are from the transition edges.

Symmetric square waves have very low even harmonic energy
content; harmonics are in the odd harmonic frequencies.

A non-symmetric rectangular (not a 'square') waveform has more
even-harmonic energy content.

with some experience you might say something else. Even harmonics are
'harmonics' too

and for many purposes it is an advantage when the odd harmonic content
is low


----
Jan-Martin, LA8AK, N-4623 Kristiansand
http://home.online.no/~la8ak/

Hmmm...I know that there are other ways to generate sampling pulses in
things like (ultra) fast sampling scopes. I suspect that similar
techniques can be used for fast edges. What little I know about that
area I can't really say much about.

After my SRD posting, I reviewed a little more in the Inventions of
Opportunity book. The late '50's fast sampling scope article
mentioned that the HP Labs researcher who saw the diode recovery
phenomenon went on to gain understanding about the mechanism involved,
and presented a paper about it at one of the semiconductor
conferences. A couple articles later in the book there's one devoted
to SRDs. They show a *20 frequency multiplier in one stage using a
SRD. Net efficiency can be pretty good, with the proper design. Just
don't want to be actually dissipating the energy that's in all the
other harmonics.

Cheers,
Tom



Roy Lewallen wrote in message ...
Tom Bruhns wrote:
. . .
. . . Seems like step
recovery diodes are not in as great favor as they once were, since
there are generally better ways to generate higher order harmonics.
. . .

Getting a bit off-topic here, but as of a few years ago, we were using
step recovery diodes to generate the step in high speed TDR systems, and
to generate the strobe for the sampling gate in high speed sampling
scopes. Rise times were on the order of 7 - 15 ps (bandwidth up to 50
GHz or so), limited primarily by circuitry external to the diodes. SRDs
replaced tunnel diodes in earlier generations of instruments. I've been
out of touch with that class of instruments for a few years now -- do
you know if something has replaced the SRD for generating fast steps, or
just for harmonic generation?

Roy Lewallen, W7EL

Hmmm...I know that there are other ways to generate sampling pulses in
things like (ultra) fast sampling scopes. I suspect that similar
techniques can be used for fast edges. What little I know about that
area I can't really say much about.

After my SRD posting, I reviewed a little more in the Inventions of
Opportunity book. The late '50's fast sampling scope article
mentioned that the HP Labs researcher who saw the diode recovery
phenomenon went on to gain understanding about the mechanism involved,
and presented a paper about it at one of the semiconductor
conferences. A couple articles later in the book there's one devoted
to SRDs. They show a *20 frequency multiplier in one stage using a
SRD. Net efficiency can be pretty good, with the proper design. Just
don't want to be actually dissipating the energy that's in all the
other harmonics.

Cheers,
Tom



Roy Lewallen wrote in message ...
Tom Bruhns wrote:
. . .
. . . Seems like step
recovery diodes are not in as great favor as they once were, since
there are generally better ways to generate higher order harmonics.
. . .

Getting a bit off-topic here, but as of a few years ago, we were using
step recovery diodes to generate the step in high speed TDR systems, and
to generate the strobe for the sampling gate in high speed sampling
scopes. Rise times were on the order of 7 - 15 ps (bandwidth up to 50
GHz or so), limited primarily by circuitry external to the diodes. SRDs
replaced tunnel diodes in earlier generations of instruments. I've been
out of touch with that class of instruments for a few years now -- do
you know if something has replaced the SRD for generating fast steps, or
just for harmonic generation?

Roy Lewallen, W7EL

In article , "Jan-Martin Noeding,
LA8AK" writes:

On 22 Feb 2004 20:39:33 GMT, (Avery Fineman)
wrote:

Sorry. If you are using the passive diode doubler looking like a
full-wave rectifier circuit, and you have a symmetric square wave,
the only harmonics you get are from the transition edges.

Symmetric square waves have very low even harmonic energy
content; harmonics are in the odd harmonic frequencies.

A non-symmetric rectangular (not a 'square') waveform has more
even-harmonic energy content.

with some experience you might say something else. Even harmonics are
'harmonics' too

OK...I'll reset my time machine and do another 52 years in the
business... :-) :-) :-)

and for many purposes it is an advantage when the odd harmonic content
is low

Outside of a step-recovery diode multiplier for an L-band sampler-locked
oscillator worked on about 1974 (oscillator at about 1.6 GHz), I've
not found much even harmonic content from a symmetric square wave.

Unsymmetric digital signals haven't been found to have much more
even harmonic content than odd harmonit content when viewed on a
spectrum analyzer...until the digital signal pulse width is VERY
short compared to its repetition time. The SRD is able to get about
as short as such pulses go and the duty cycle is in fractions of a
percent. [also "avalanche diode" which I'm sure that someone will
bring up sooner or later to start another argument...:-) ]

The original question was about "practical multiplier stages." Those
would range from doublers to quintuplers. Going much higher HAS
been done but it takes VERY expensive lab instruments to prove
them out, such as with an SRD "comb generator." Comb generators
have all sorts of harmonics but trying to extract, say, the 21st without
passing the 20th or 22nd harmonic requires a very fussy high-Q filter.
Some of the things _possible_ are not quite in the homebrewer
workshop category...or they take a LOT of time to complete.

I mentioned the passive diode doubler for the simple reason it IS
simple when used with a distorted sinewave source (not a square
wave). The effect of the two diodes in a "full-wave rectifier like"
circuit creates an artificial 2nd harmonic by adding one sinusoid
swing with the other, opposite-polarity sinusoid swing inverted by
transformer action. Jim Pennell commented on that previously
(and quite correctly). That makes for a broadband, non-fussy
doubler circuit. Old thing and not a super whiz-bang state-of-the-
art, hot-off-the-drawing-board wonder but it works. :-)

Len Anderson
retired (from regular hours) electronic engineer person

In article , "Jan-Martin Noeding,
LA8AK" writes:

On 22 Feb 2004 20:39:33 GMT, (Avery Fineman)
wrote:

Sorry. If you are using the passive diode doubler looking like a
full-wave rectifier circuit, and you have a symmetric square wave,
the only harmonics you get are from the transition edges.

Symmetric square waves have very low even harmonic energy
content; harmonics are in the odd harmonic frequencies.

A non-symmetric rectangular (not a 'square') waveform has more
even-harmonic energy content.

with some experience you might say something else. Even harmonics are
'harmonics' too

OK...I'll reset my time machine and do another 52 years in the
business... :-) :-) :-)

and for many purposes it is an advantage when the odd harmonic content
is low

Outside of a step-recovery diode multiplier for an L-band sampler-locked
oscillator worked on about 1974 (oscillator at about 1.6 GHz), I've
not found much even harmonic content from a symmetric square wave.

Unsymmetric digital signals haven't been found to have much more
even harmonic content than odd harmonit content when viewed on a
spectrum analyzer...until the digital signal pulse width is VERY
short compared to its repetition time. The SRD is able to get about
as short as such pulses go and the duty cycle is in fractions of a
percent. [also "avalanche diode" which I'm sure that someone will
bring up sooner or later to start another argument...:-) ]

The original question was about "practical multiplier stages." Those
would range from doublers to quintuplers. Going much higher HAS
been done but it takes VERY expensive lab instruments to prove
them out, such as with an SRD "comb generator." Comb generators
have all sorts of harmonics but trying to extract, say, the 21st without
passing the 20th or 22nd harmonic requires a very fussy high-Q filter.
Some of the things _possible_ are not quite in the homebrewer
workshop category...or they take a LOT of time to complete.

I mentioned the passive diode doubler for the simple reason it IS
simple when used with a distorted sinewave source (not a square
wave). The effect of the two diodes in a "full-wave rectifier like"
circuit creates an artificial 2nd harmonic by adding one sinusoid
swing with the other, opposite-polarity sinusoid swing inverted by
transformer action. Jim Pennell commented on that previously
(and quite correctly). That makes for a broadband, non-fussy
doubler circuit. Old thing and not a super whiz-bang state-of-the-
art, hot-off-the-drawing-board wonder but it works. :-)

Len Anderson
retired (from regular hours) electronic engineer person

(Avery Fineman) wrote in message ...

Unsymmetric digital signals haven't been found to have much more
even harmonic content than odd harmonit content when viewed on a
spectrum analyzer...until the digital signal pulse width is VERY
short compared to its repetition time.

Huh? Try a 1/3 -- 2/3 ratio. NO third harmonic (or sixth or ninth,
etc); second is the greatest amplitude harmonic at fully 1/2 the
fundamental amplitude. Fourth is larger than the fifth. For a
symmetric square wave, there's no second and the third is only 1/3 the
amplitude of the fundamental. Easy to verify with a spectrum analyzer
or through a Fourier series. As the pulse width goes to zero, the
fundamental and all harmonics go to equal amplitudes. At 5% pulse
width, for example, the harmonic amplitudes decrease monotonically as
harmonic number increases, out to the twentieth, which is a null, but
even the 12th is fully 50% of the fundamental.

This is useful info if you're trying to design a simple amplifier-type
doubler; adjusting the conduction angle to approximately 1/3 will give
you lots of second but little third, making it easier to filter the
output. But if you weren't thinking about it and tried to make a
tripler, and accidentally made your conduction angle 1/3, you might
wonder why you were having so much trouble getting good tripler
efficiency.

Cheers,
Tom