If I understand correctly, you're interested in harmonics up in the
70MHz region. To me it seems silly to use diodes capable of
generating a comb of harmonics out to 20GHz for that. An advantage--a
big advantage--of the tiny logic is that you get considerable power
gain in the stage, and the sot-23 package is likely no larger than the
diode you might have used anyway. The edges, as others have pointed
out, are PLENTY fast enough for what I believe you want to do.

Whether you use diodes or gates, your size problem will be the
harmonic-selection filter. As you've learned (and I trust not
forgotten already), you need either multiple poles in your filter or a
rather high Q. You _could_ get the high Q with crystals, but of
course then you're locked down to particular frequencies. For high
multiplication factors to low-VHF frequencies, it's probably hard to
beat a PLL for (potentially) small size.

In offering suggestions, it would also be helpful to us to know your
actual needs for signal purity, both close-in (phase noise) and
broadband (other harmonics, etc.)

If you do use diodes for higher-order harmonic generation, and not
just a simple full-wave-rectifier type frequency doubler, I suppose
you want something of the nature of a step recovery diode. That
implies minority carrier stored charge in the diode, and that would
preclude using a Schottky diode (which would work great in the
full-wave-rectifier type doubler). If you get into actually wanting
to generate harmonic combs out to microwave frequencies, it's probably
worthwhile looking for diodes actually characterized for step recovery
service. But I really think that's way beyond what you are trying to
accomplish right now.

Cheers,
Tom


Paul Burridge wrote in message . ..
On Sun, 11 Apr 2004 14:14:56 +0200, "Fred Bartoli"
r_AndThisToo wrote:

Don't let Paul dream too much about picoseconds.

Well, quite. I wouldn't know what to do with all those extra
harmonics, anyway. :-)
Diodes sound great, but I'm heavily put off by that comment earlier in
the thread that they're prone to self oscillation. :-( What's a
"parametric device" anyway?

In order to achieve results that good, one have to pay very careful
attention to "wiring". There's still a lot of room for Paul to improve his
PCB design skills ;-)

Fair comment. But I *am* working on it!

If you do use diodes for higher-order harmonic generation, and not
just a simple full-wave-rectifier type frequency doubler, I suppose
you want something of the nature of a step recovery diode. That
implies minority carrier stored charge in the diode, and that would
preclude using a Schottky diode (which would work great in the
full-wave-rectifier type doubler). If you get into actually wanting
to generate harmonic combs out to microwave frequencies, it's probably
worthwhile looking for diodes actually characterized for step recovery
service. But I really think that's way beyond what you are trying to
accomplish right now.

My turn to learn something here. Tom, would you elaborate a bit on the above
please? I know SRD's are comb generators out to visible light, but they're
also 50 percent hard to find and 50 percent magic. I've been using
Schottky's for X16 multipliers to 2 GHz, am I doing something wrong? (I keep
promising myself that I'm gonna substitute an MMIC for that one day, I DID
find the "Filter Gain" in the line length from generator to filter), THAT
was both impressive AND helpful. If I go with the MMIC, any preference of
Silicon over GaAs?

Regards

W4ZCB

On Mon, 12 Apr 2004 19:09:51 GMT, "Harold E. Johnson"
wrote:


If you do use diodes for higher-order harmonic generation, and not
just a simple full-wave-rectifier type frequency doubler, I suppose
you want something of the nature of a step recovery diode. That
implies minority carrier stored charge in the diode, and that would
preclude using a Schottky diode (which would work great in the
full-wave-rectifier type doubler). If you get into actually wanting
to generate harmonic combs out to microwave frequencies, it's probably
worthwhile looking for diodes actually characterized for step recovery
service. But I really think that's way beyond what you are trying to
accomplish right now.

My turn to learn something here. Tom, would you elaborate a bit on the above
please? I know SRD's are comb generators out to visible light, but they're
also 50 percent hard to find and 50 percent magic. I've been using
Schottky's for X16 multipliers to 2 GHz, am I doing something wrong? (I keep
promising myself that I'm gonna substitute an MMIC for that one day, I DID
find the "Filter Gain" in the line length from generator to filter), THAT
was both impressive AND helpful. If I go with the MMIC, any preference of
Silicon over GaAs?

Regards

W4ZCB


The only distributor-stock SRDs I know of are the M/Acom MA44767,
MA44768, MA44769 parts, all SOT-23 and dirt cheap. I think Penstock
carries them. The '68 or '69 should be good for multiplication to 2
GHz. For high ratios, an SRD will beat a plain diode by a huge amount.
There are lots of appnotes around about using them as multipliers.

I have a bunch in stock and can send a few to anybody who wants to
play.

John

The only distributor-stock SRDs I know of are the M/Acom MA44767,
MA44768, MA44769 parts, all SOT-23 and dirt cheap. I think Penstock
carries them. The '68 or '69 should be good for multiplication to 2
GHz. For high ratios, an SRD will beat a plain diode by a huge amount.
There are lots of appnotes around about using them as multipliers.

I have a bunch in stock and can send a few to anybody who wants to
play.

I'd like to talk you out of a couple, and thanks for the supplier info.
Wonder what MaCom's min order is? Anything you need in trade or a few green
stamps?

W4ZCB
Call Book Address.

On Mon, 12 Apr 2004 22:16:01 GMT, "Harold E. Johnson"
wrote:




The only distributor-stock SRDs I know of are the M/Acom MA44767,
MA44768, MA44769 parts, all SOT-23 and dirt cheap. I think Penstock
carries them. The '68 or '69 should be good for multiplication to 2
GHz. For high ratios, an SRD will beat a plain diode by a huge amount.
There are lots of appnotes around about using them as multipliers.

I have a bunch in stock and can send a few to anybody who wants to
play.

I'd like to talk you out of a couple, and thanks for the supplier info.
Wonder what MaCom's min order is? Anything you need in trade or a few green
stamps?

W4ZCB
Call Book Address.

^^^^^^^^^^^^^^^^^^ don't have one. Email me, with hopefully obvious
despam.

John

"John Larkin" wrote in
message ...


W4ZCB
Call Book Address.

^^^^^^^^^^^^^^^^^^ don't have one. Email me, with hopefully obvious
despam.

http://qrz.com/callsign/w4zcb

"PM"

"John Larkin" wrote in
message ...


W4ZCB
Call Book Address.

^^^^^^^^^^^^^^^^^^ don't have one. Email me, with hopefully obvious
despam.

http://qrz.com/callsign/w4zcb

"PM"

On Mon, 12 Apr 2004 22:16:01 GMT, "Harold E. Johnson"
wrote:




The only distributor-stock SRDs I know of are the M/Acom MA44767,
MA44768, MA44769 parts, all SOT-23 and dirt cheap. I think Penstock
carries them. The '68 or '69 should be good for multiplication to 2
GHz. For high ratios, an SRD will beat a plain diode by a huge amount.
There are lots of appnotes around about using them as multipliers.

I have a bunch in stock and can send a few to anybody who wants to
play.

I'd like to talk you out of a couple, and thanks for the supplier info.
Wonder what MaCom's min order is? Anything you need in trade or a few green
stamps?

W4ZCB
Call Book Address.

^^^^^^^^^^^^^^^^^^ don't have one. Email me, with hopefully obvious
despam.

John

The only distributor-stock SRDs I know of are the M/Acom MA44767,
MA44768, MA44769 parts, all SOT-23 and dirt cheap. I think Penstock
carries them. The '68 or '69 should be good for multiplication to 2
GHz. For high ratios, an SRD will beat a plain diode by a huge amount.
There are lots of appnotes around about using them as multipliers.

I have a bunch in stock and can send a few to anybody who wants to
play.

I'd like to talk you out of a couple, and thanks for the supplier info.
Wonder what MaCom's min order is? Anything you need in trade or a few green
stamps?

W4ZCB
Call Book Address.

On Mon, 12 Apr 2004 12:23:09 -0700, John Larkin
wrote:



The only distributor-stock SRDs I know of are the M/Acom MA44767,
MA44768, MA44769 parts, all SOT-23 and dirt cheap. I think Penstock
carries them. The '68 or '69 should be good for multiplication to 2
GHz. For high ratios, an SRD will beat a plain diode by a huge amount.
There are lots of appnotes around about using them as multipliers.

I have a bunch in stock and can send a few to anybody who wants to
play.

MPulse microwave used to be pretty good with samples, I have some
MP4065 SRDs that work well.

Tel # used to be 408 432 1480

Barry lennox