"Tom Bruhns" Wrote:


(Avery Fineman) wrote in message
...

... Suffice to say
that a square wave cannot be used with a passive
diode doubler; all the energy is contained in
the short transition times and that is rarely
enough to be worth it.

?? Lots of energy in the fundamental; filter to
extract the fundamental and feed it to your
full-wave rectifier doubler.
Efficiency can be high if the filter does
not cause dissipation in the
source at the harmonics.

Tom, look at it this way... Draw the square wave, assuming capacitive
coupling so it has a zero crossing. Then draw the same signal but invert
the negative going half to positive, which is what the full wave diode
doubler would do.

You wind up with a positive voltage, but with VERY narrow negative spikes.

So, a square wave into a diode doubler will produce only a small amount of
the second harmonic. You'd be better off running the input square wave
through a lowpass of some sort and then doubling it.

Given a sine wave input, there is a fair amount of negative going signal
and that is what produces the high energy content of the second harmonic.


Jim Pennell
N6BIU

On Sat, 21 Feb 2004 12:28:11 +0000, Paul Burridge
wrote:

On Sat, 21 Feb 2004 03:20:07 -0800, Roy Lewallen
wrote:

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?

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

made some experiments 10-15 years ago with doublers to 144Mc/s, and
they probably would work on at least 200Mc. Best experience with a
BFR90 amplifier following the 'rectifier', see
http://home.online.no/~la8ak/c13.htm
It was important with certain dc load following the diodes and some
bias current

Another interesting multiplier used for 100kc calibrator - on vhf -
described in UKW Berichte uses quad nand schmidt trigger, where the
input signal is splitted - one part to a nand input and the other to
3x nand gates connected as inverters and connected to the second input
of the nand-gate such that the truth table said constant logic high
output, but a very thin spike occured because of the transition time
delay

73
JM
----
Jan-Martin, LA8AK, N-4623 Kristiansand
http://home.online.no/~la8ak/

On Sat, 21 Feb 2004 12:28:11 +0000, Paul Burridge
wrote:

On Sat, 21 Feb 2004 03:20:07 -0800, Roy Lewallen
wrote:

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?

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

made some experiments 10-15 years ago with doublers to 144Mc/s, and
they probably would work on at least 200Mc. Best experience with a
BFR90 amplifier following the 'rectifier', see
http://home.online.no/~la8ak/c13.htm
It was important with certain dc load following the diodes and some
bias current

Another interesting multiplier used for 100kc calibrator - on vhf -
described in UKW Berichte uses quad nand schmidt trigger, where the
input signal is splitted - one part to a nand input and the other to
3x nand gates connected as inverters and connected to the second input
of the nand-gate such that the truth table said constant logic high
output, but a very thin spike occured because of the transition time
delay

73
JM
----
Jan-Martin, LA8AK, N-4623 Kristiansand
http://home.online.no/~la8ak/

In article , (Tom
Bruhns) writes:

(Avery Fineman) wrote in message
...
... Suffice to say
that a square wave cannot be used with a passive diode doubler; all
the energy is contained in the short transition times and that is rarely
enough to be worth it.

?? Lots of energy in the fundamental; filter to extract the
fundamental and feed it to your full-wave rectifier doubler.
Efficiency can be high if the filter does not cause dissipation in the
source at the harmonics.

In article , (Tom
Bruhns) writes:

(Avery Fineman) wrote in message
...
... Suffice to say
that a square wave cannot be used with a passive diode doubler; all
the energy is contained in the short transition times and that is rarely
enough to be worth it.

?? Lots of energy in the fundamental; filter to extract the
fundamental and feed it to your full-wave rectifier doubler.
Efficiency can be high if the filter does not cause dissipation in the
source at the harmonics.

In article , (Tom
Bruhns) writes:

(Avery Fineman) wrote in message
...
... Suffice to say
that a square wave cannot be used with a passive diode doubler; all
the energy is contained in the short transition times and that is rarely
enough to be worth it.

?? Lots of energy in the fundamental; filter to extract the
fundamental and feed it to your full-wave rectifier doubler.
Efficiency can be high if the filter does not cause dissipation in the
source at the harmonics.

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.

Len Anderson
retired (from regular hours) electronic engineer person


Apologies tendered for inappropriate, incomplete prior posting. Bell's
machine rang for a talk about another subject thread and I forgot to
complete this one. :-( LHA

In article , (Tom
Bruhns) writes:

(Avery Fineman) wrote in message
...
... Suffice to say
that a square wave cannot be used with a passive diode doubler; all
the energy is contained in the short transition times and that is rarely
enough to be worth it.

?? Lots of energy in the fundamental; filter to extract the
fundamental and feed it to your full-wave rectifier doubler.
Efficiency can be high if the filter does not cause dissipation in the
source at the harmonics.

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.

Len Anderson
retired (from regular hours) electronic engineer person


Apologies tendered for inappropriate, incomplete prior posting. Bell's
machine rang for a talk about another subject thread and I forgot to
complete this one. :-( LHA

"Jim Pennell" wrote in message link.net...
"Tom Bruhns" Wrote:
....
?? Lots of energy in the fundamental; filter to
extract the fundamental and feed it to your
full-wave rectifier doubler.
....
So, a square wave into a diode doubler will produce only a small amount of
the second harmonic. You'd be better off running the input square wave
through a lowpass of some sort and then doubling it.

Right on, Jim. "Filter to extract the fundamental and feed it [the
fundamental] to your full-wave rectifier doubler." Of course, third
harmonic mixed with fundamental gives you second and fourth, etc., so
there's a hint that the harmonics could be useful if the phases were
right. What do you get if you feed a mixer a square wave in one port,
and the same square wave delayed by 1/4 period into the other port?

Cheers,
Tom

"Jim Pennell" wrote in message link.net...
"Tom Bruhns" Wrote:
....
?? Lots of energy in the fundamental; filter to
extract the fundamental and feed it to your
full-wave rectifier doubler.
....
So, a square wave into a diode doubler will produce only a small amount of
the second harmonic. You'd be better off running the input square wave
through a lowpass of some sort and then doubling it.

Right on, Jim. "Filter to extract the fundamental and feed it [the
fundamental] to your full-wave rectifier doubler." Of course, third
harmonic mixed with fundamental gives you second and fourth, etc., so
there's a hint that the harmonics could be useful if the phases were
right. What do you get if you feed a mixer a square wave in one port,
and the same square wave delayed by 1/4 period into the other port?

Cheers,
Tom

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

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

In article , (Tom
Bruhns) writes:

(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.

Thank you, Tom...but I've done the "SineX over X" thing a few times
already and looked at a lot of spectral displays. Even wrote a
computer program or three to determine the harmonic content of
various arbitrary-shaped defined waveforms (two for corporate use,
one in a shareware/freeware package).

The first null of ALL harmonics occurs at frequencies at the inverse
of the repetition time of the waveform. That turns out to be fairly
true for any waveform, not just a pulse. Trouble is, the harmonic
content NOT at the major null increments varies considerably in
actual practice since the source of RF being multiplied varies in
shape in actual practice.

Discussing harmonic content is so much bafflegab without first
defining the source's waveform shape...even if to coarse levels
of square wave versus sinusoid versus pulse or whatever.

The kickoff message to this thread started with "square wave"
and all I did was further refine that to symmetical square wave.
You aren't going to tell me there's a lot of even harmonic energy
in a symmetric square wave because I can set it up on the bench
and demonstrate it doesn't. Practical test versus theoretical and
results match.

I once managed to phase-lock a pulse generator in order to key
on a signal generator output for exactly ONE RF cycle (35 db on-
off ratio). Interesting broad spectral content, way wide almost
like an SRD output. Impractical, of course, was to satisfy a
couple of others arguing the whichness or the what one day. :-)

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.

Well, I'm not wondering at all since I haven't built any vacuum tube
or FET active multipliers, just the bipolar transistor types that don't
quite fit into the old "conduction angle" simple rules.

Correction: Built a tube crystal oscillator (6AK6) that doubled or
tripled (as desired by tuning) to be the LO for a 6BE6 pentagrid
running at external LO injection. Behaved like a fundamental
crystal oscillator that doubled or trippled in the plate. That was
around 1960 and didn't have the tools to check waveforms on my
lunch hours. :-) Just played with it until it worked...and had
enough LO injection to run the pentagrid at good conversion
transconductance.

Why bother to use frequency multiplier stages NOW when PLLs
and DDSs can have oscillators at their fundamental and those can
be divided down with available parts to a low, stable lock frequency?
It's fine for restoring antiques to use lots of multipliers, but, let's
face it, those can be a pain in the expletive deleted to recreate now.
Others' mileage varies, of course.

I mentioned a simple two-diode "full-wave" doubler because it is an
easy thing to implement and is broadband to start with...no fussing
with tuned-circuit impedances at the start to make it work with a
non-square source waveform. It may not be as efficient as some
would like but it is easy to do compared to direct active doublers.

Len Anderson
retired (from regular hours) electronic engineer person

In article , (Tom
Bruhns) writes:

(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.

Thank you, Tom...but I've done the "SineX over X" thing a few times
already and looked at a lot of spectral displays. Even wrote a
computer program or three to determine the harmonic content of
various arbitrary-shaped defined waveforms (two for corporate use,
one in a shareware/freeware package).

The first null of ALL harmonics occurs at frequencies at the inverse
of the repetition time of the waveform. That turns out to be fairly
true for any waveform, not just a pulse. Trouble is, the harmonic
content NOT at the major null increments varies considerably in
actual practice since the source of RF being multiplied varies in
shape in actual practice.

Discussing harmonic content is so much bafflegab without first
defining the source's waveform shape...even if to coarse levels
of square wave versus sinusoid versus pulse or whatever.

The kickoff message to this thread started with "square wave"
and all I did was further refine that to symmetical square wave.
You aren't going to tell me there's a lot of even harmonic energy
in a symmetric square wave because I can set it up on the bench
and demonstrate it doesn't. Practical test versus theoretical and
results match.

I once managed to phase-lock a pulse generator in order to key
on a signal generator output for exactly ONE RF cycle (35 db on-
off ratio). Interesting broad spectral content, way wide almost
like an SRD output. Impractical, of course, was to satisfy a
couple of others arguing the whichness or the what one day. :-)

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.

Well, I'm not wondering at all since I haven't built any vacuum tube
or FET active multipliers, just the bipolar transistor types that don't
quite fit into the old "conduction angle" simple rules.

Correction: Built a tube crystal oscillator (6AK6) that doubled or
tripled (as desired by tuning) to be the LO for a 6BE6 pentagrid
running at external LO injection. Behaved like a fundamental
crystal oscillator that doubled or trippled in the plate. That was
around 1960 and didn't have the tools to check waveforms on my
lunch hours. :-) Just played with it until it worked...and had
enough LO injection to run the pentagrid at good conversion
transconductance.

Why bother to use frequency multiplier stages NOW when PLLs
and DDSs can have oscillators at their fundamental and those can
be divided down with available parts to a low, stable lock frequency?
It's fine for restoring antiques to use lots of multipliers, but, let's
face it, those can be a pain in the expletive deleted to recreate now.
Others' mileage varies, of course.

I mentioned a simple two-diode "full-wave" doubler because it is an
easy thing to implement and is broadband to start with...no fussing
with tuned-circuit impedances at the start to make it work with a
non-square source waveform. It may not be as efficient as some
would like but it is easy to do compared to direct active doublers.

Len Anderson
retired (from regular hours) electronic engineer person

Just did an interesting little 'speriment. Standard diode "full wave
rectifier" frequency doubler. Transformer is 16 trifilar turns on an
FT50-43 core (should be a bit more than 50uH per section). One of the
triplet is the primary, and the other two are connected as a
center-tapped secondary. The diodes are 1N4007 -- yep, the 1kV
mains-freq rectifiers. Excitation comes from an HP3326, set to square
wave output, source impedance 50 ohms. 50 ohm load impedance on the
doubler output (input to spectrum analyzer; DC coupled load). HP3326
square wave risetime is about 10 nanoseconds, I believe. Excite at
0.5MHz, +/-2V (4Vp-p) Output waveform observed on a fast scope is
frequency-doubled, close to 50% duty cycle, with fast falling edges
and slow (200nsec) rising edges. Amplitude about 2Vp-p. Strong
spectral output on all even harmonics; all odds suppressed about 20dB
from the low evens, and I'm sure would be much lower with better
matching of the diodes.

Explanation left as an exercise for the reader, but should be obvious
from previous discussion here. I'd guess 1N4148-type diodes would
behave similarly for an input around 100MHz.

Cheers,
Tom

(Tom Bruhns) wrote in message om...
(Avery Fineman) wrote in message ...
... Suffice to say
that a square wave cannot be used with a passive diode doubler; all
the energy is contained in the short transition times and that is rarely
enough to be worth it.

?? Lots of energy in the fundamental; filter to extract the
fundamental and feed it to your full-wave rectifier doubler.
Efficiency can be high if the filter does not cause dissipation in the
source at the harmonics.

Just did an interesting little 'speriment. Standard diode "full wave
rectifier" frequency doubler. Transformer is 16 trifilar turns on an
FT50-43 core (should be a bit more than 50uH per section). One of the
triplet is the primary, and the other two are connected as a
center-tapped secondary. The diodes are 1N4007 -- yep, the 1kV
mains-freq rectifiers. Excitation comes from an HP3326, set to square
wave output, source impedance 50 ohms. 50 ohm load impedance on the
doubler output (input to spectrum analyzer; DC coupled load). HP3326
square wave risetime is about 10 nanoseconds, I believe. Excite at
0.5MHz, +/-2V (4Vp-p) Output waveform observed on a fast scope is
frequency-doubled, close to 50% duty cycle, with fast falling edges
and slow (200nsec) rising edges. Amplitude about 2Vp-p. Strong
spectral output on all even harmonics; all odds suppressed about 20dB
from the low evens, and I'm sure would be much lower with better
matching of the diodes.

Explanation left as an exercise for the reader, but should be obvious
from previous discussion here. I'd guess 1N4148-type diodes would
behave similarly for an input around 100MHz.

Cheers,
Tom

(Tom Bruhns) wrote in message om...
(Avery Fineman) wrote in message ...
... Suffice to say
that a square wave cannot be used with a passive diode doubler; all
the energy is contained in the short transition times and that is rarely
enough to be worth it.

?? Lots of energy in the fundamental; filter to extract the
fundamental and feed it to your full-wave rectifier doubler.
Efficiency can be high if the filter does not cause dissipation in the
source at the harmonics.

On 24 Feb 2004 13:00:57 -0800, (Tom Bruhns) wrote:

Just did an interesting little 'speriment. Standard diode "full wave
rectifier" frequency doubler. Transformer is 16 trifilar turns on an
FT50-43 core (should be a bit more than 50uH per section). One of the
triplet is the primary, and the other two are connected as a
center-tapped secondary. The diodes are 1N4007 -- yep, the 1kV
mains-freq rectifiers. Excitation comes from an HP3326, set to square
wave output, source impedance 50 ohms. 50 ohm load impedance on the
doubler output (input to spectrum analyzer; DC coupled load). HP3326
square wave risetime is about 10 nanoseconds, I believe. Excite at
0.5MHz, +/-2V (4Vp-p) Output waveform observed on a fast scope is
frequency-doubled, close to 50% duty cycle, with fast falling edges
and slow (200nsec) rising edges. Amplitude about 2Vp-p. Strong
spectral output on all even harmonics; all odds suppressed about 20dB
from the low evens, and I'm sure would be much lower with better
matching of the diodes.

Explanation left as an exercise for the reader, but should be obvious
from previous discussion here. I'd guess 1N4148-type diodes would
behave similarly for an input around 100MHz.

Great. So can you guys now agree on the most appropriate waveshape to
generate the maximum amount of even harmonics?
--

The BBC: Licensed at public expense to spread lies.

On 24 Feb 2004 13:00:57 -0800, (Tom Bruhns) wrote:

Just did an interesting little 'speriment. Standard diode "full wave
rectifier" frequency doubler. Transformer is 16 trifilar turns on an
FT50-43 core (should be a bit more than 50uH per section). One of the
triplet is the primary, and the other two are connected as a
center-tapped secondary. The diodes are 1N4007 -- yep, the 1kV
mains-freq rectifiers. Excitation comes from an HP3326, set to square
wave output, source impedance 50 ohms. 50 ohm load impedance on the
doubler output (input to spectrum analyzer; DC coupled load). HP3326
square wave risetime is about 10 nanoseconds, I believe. Excite at
0.5MHz, +/-2V (4Vp-p) Output waveform observed on a fast scope is
frequency-doubled, close to 50% duty cycle, with fast falling edges
and slow (200nsec) rising edges. Amplitude about 2Vp-p. Strong
spectral output on all even harmonics; all odds suppressed about 20dB
from the low evens, and I'm sure would be much lower with better
matching of the diodes.

Explanation left as an exercise for the reader, but should be obvious
from previous discussion here. I'd guess 1N4148-type diodes would
behave similarly for an input around 100MHz.

Great. So can you guys now agree on the most appropriate waveshape to
generate the maximum amount of even harmonics?
--

The BBC: Licensed at public expense to spread lies.