"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