A neat and compact way to generate RF harmonics...

[Paul Burridge]

HI guys,

Easter greetings and all that old crap.

Now, I've been using 74HC series hex inverters to generate odd order
harmonics and now I've got the hang of biasing them properly, they
seem to work rather well. However, they're rather *large* by today's
standards, even in the smaller packages and I don't need 6 gates per
package so there's a lot of redundancy. Soldering decoupling caps on
the ill-conceived gnd and +V diagonal opposite pins also looks untidy.
What's a better device with a smaller footprint with sub 7nS r/f
times? I thought about maybe an SMD varactor? What does the panel
think? Even harmonics are fine, BTW.

Thanks,

p.

 

[Uwe Bonnes]

Paul Burridge <pb@notthisbit.osiris1.co.uk> wrote:
: HI guys,

: Easter greetings and all that old crap.

: Now, I've been using 74HC series hex inverters to generate odd order
: harmonics and now I've got the hang of biasing them properly, they
: seem to work rather well. However, they're rather *large* by today's
: standards, even in the smaller packages and I don't need 6 gates per
: package so there's a lot of redundancy. Soldering decoupling caps on
: the ill-conceived gnd and +V diagonal opposite pins also looks untidy.
: What's a better device with a smaller footprint with sub 7nS r/f
: times? I thought about maybe an SMD varactor? What does the panel
: think? Even harmonics are fine, BTW.

Look for Single Gate SOT23/SC packages...
--
Uwe Bonnes bon@elektron.ikp.physik.tu-darmstadt.de

Institut fuer Kernphysik Schlossgartenstrasse 9 64289 Darmstadt
--------- Tel. 06151 162516 -------- Fax. 06151 164321 ----------

 

[John Larkin]

On Fri, 09 Apr 2004 14:38:13 +0100, Paul Burridge
<pb@notthisbit.osiris1.co.uk> wrote:

HI guys,

Easter greetings and all that old crap.

Now, I've been using 74HC series hex inverters to generate odd order
harmonics and now I've got the hang of biasing them properly, they
seem to work rather well. However, they're rather *large* by today's
standards, even in the smaller packages and I don't need 6 gates per
package so there's a lot of redundancy. Soldering decoupling caps on
the ill-conceived gnd and +V diagonal opposite pins also looks untidy.
What's a better device with a smaller footprint with sub 7nS r/f
times? I thought about maybe an SMD varactor? What does the panel
think? Even harmonics are fine, BTW.

Thanks,

p.

TI, Onsemi, and Fairchild make tiny-logic gates, in SOT-23 or smaller
packages. The faster ones have seriously sub-ns transition times.

A step-recovery diode can make a pulse that's tens of volts with
risetime in the 100 ps ballpark, but their drive circuits will gobble
up board area.

John

 

[Leon Heller]

"Paul Burridge" <pb@notthisbit.osiris1.co.uk> wrote in message
news:ao8d70lj4268ns4i2864lbq2f7113chdff@4ax.com...

HI guys,

Easter greetings and all that old crap.

Now, I've been using 74HC series hex inverters to generate odd order
harmonics and now I've got the hang of biasing them properly, they
seem to work rather well. However, they're rather *large* by today's
standards, even in the smaller packages and I don't need 6 gates per
package so there's a lot of redundancy. Soldering decoupling caps on
the ill-conceived gnd and +V diagonal opposite pins also looks untidy.
What's a better device with a smaller footprint with sub 7nS r/f
times? I thought about maybe an SMD varactor? What does the panel
think? Even harmonics are fine, BTW.

Avalanche transistor. Some ordinary BJTs will work in avalanche mode.

Leon

 

[Joerg]

I think what Uwe mentioned is called TinyLogic. I forgot the company but
believe it was either TI or Fairchild. Some of them do come in SOT23-5 and
other packages. Pretty neat stuff.

Then again, why not generate harmonics the old fashioned way, using UHF
transistors? Some of these are really small.

Regards, Joerg.

Paul Burridge wrote:

HI guys,

Easter greetings and all that old crap.

Now, I've been using 74HC series hex inverters to generate odd order
harmonics and now I've got the hang of biasing them properly, they
seem to work rather well. However, they're rather *large* by today's
standards, even in the smaller packages and I don't need 6 gates per
package so there's a lot of redundancy. Soldering decoupling caps on
the ill-conceived gnd and +V diagonal opposite pins also looks untidy.
What's a better device with a smaller footprint with sub 7nS r/f
times? I thought about maybe an SMD varactor? What does the panel
think? Even harmonics are fine, BTW.

Thanks,

p.

 

[Mac]

On Fri, 09 Apr 2004 14:38:13 +0100, Paul Burridge wrote:

HI guys,

Easter greetings and all that old crap.

Now, I've been using 74HC series hex inverters to generate odd order
harmonics and now I've got the hang of biasing them properly, they
seem to work rather well. However, they're rather *large* by today's
standards, even in the smaller packages and I don't need 6 gates per
package so there's a lot of redundancy. Soldering decoupling caps on
the ill-conceived gnd and +V diagonal opposite pins also looks untidy.
What's a better device with a smaller footprint with sub 7nS r/f
times? I thought about maybe an SMD varactor? What does the panel
think? Even harmonics are fine, BTW.

Thanks,

p.

I believe the AC logic family drives a lot harder than the HC logic
family, so you should get more and higher harmonics. I'm sure they're
available in soics or perhaps even smaller packages.

--Mac

 

[Paul Burridge]

On Sat, 10 Apr 2004 08:22:21 GMT, Robert Baer
<robertbaer@earthlink.net> wrote:

Not a varactor (diode), but a switching diode; fast. Snap-off is lotz
better.
And they are a *LOT* smaller!

Thanks, Robert (and all else)
I'd prefer a diode solution as there'd be no power supply requirements
for each device. The tiny size is an added bonus, of course. But
what's the drawback with superfast switching diodes as against active
inverters? I'm sure there must be (at least) one...