|
|
Rules of Thumb - RF Cafe Forums
|
Kirt Blattenberger
|
Post subject: Rules of Thumb
Posted: Wed May 24, 2006 11:34 pm
|
|
|
Site Admin |
|
Joined: Sun Aug 03, 2003
2:02 pm Posts: 451 Location: Erie, PA
|
Greetings:
This post is a compliment to my
May 25, 2006, Factoid on the IP3 versus P1dB power
rule of thumb. I would like to collect as many other
rules of thumb for the industry as possible, and
will create a separate webpage for them if enough
are provided by vauled visitors (that would be you).
Thanks for your help.
_________________ - Kirt Blattenberger
RF Cafe Progenitor & Webmaster
|
|
|
|
|
VSWR |
Post subject: Another
Posted: Thu May 25, 2006 3:12 pm
|
|
Joined: Sun Jan 11, 2004
4:44 pm Posts: 16 |
One I use all the time is for the inductance of
bondwires (1 mil gold). The rule of thumb goes that
the bondwire's inductance in nH is approximately
equal to its length in mm. The equivalent
for length in mils (0.001 in.) is approximately
25 pH per mil (25.4 pH actually, since 1 mil = 0.0254
mm, but since we're approximating here...).
VSWR .
|
|
|
|
|
The Amplifier |
Post subject:
Posted: Tue May 30, 2006 8:44 am
|
|
|
Captain |
|
Joined: Fri Jul 16, 2004
4:08 pm Posts: 5 |
Hey Kirt here's another one for your list.
"A PCB trace or coaxial cable mus tbe treated
as a transmission line when its length is more than
1/10 of a wavelength."
This is because at
that point the reflections can set up significant
standing waves along the path.
|
|
|
|
|
Ming |
Post subject:
Posted: Tue May 30, 2006 12:12 pm
|
|
|
Captain |
|
Joined: Tue Jan 13, 2004
8:42 am Posts: 7 |
Good idea with this list. COme on guys, let's get
with it
Um..... here's mine If you're looking
at a spectrum analyzer display and see a spectral
line and you need to determine whether it's a discrete
spur, try increasing or decreasing the resolution
BW control. If the noise floor power level changes
but the amplitude of the spur does not, then it's
a discrete spur. I'm amazed at the numbe
rof guys I work with don't know that simple test.
The reason it works is because a discrete spur has
no significant content other than at its discrete
frequency, so the BW of the filter does not affect
its power level (as long as your signal is not on
the skirt (band edge) of the filter. Any
way, that's mine. Let's have more.............
|
|
|
|
|
kpainter |
Post subject:
Posted: Fri Jun 02, 2006 7:21 pm
|
|
|
General |
|
Joined: Wed Aug 20, 2003
11:47 am Posts: 84 Location: Santa Barbara,
CA |
|
|
|
|
Snerdly |
Post subject:
Posted: Mon Jun 05, 2006 11:33 pm
|
|
|
Captain |
|
Joined: Fri Jul 16, 2004
4:10 pm Posts: 8 Location: Tennessee
|
Hey thanks for that great list! They have a lot
I've never heard of.
I'm sure I've got one
to add to it, but I'm going to have to think real
hard.
I'll be back...
|
|
|
|
|
Curtis Crow |
Post subject:
Posted: Tue Jun 06, 2006 1:51 pm
|
|
|
Captain |
|
Joined: Wed Jan 07, 2004
1:27 pm Posts: 10 |
1 meter = 300 MHz (in air)
|
|
|
|
|
Kirt Blattenberger
|
Post subject:
Posted: Sat Jun 10, 2006 9:13 pm
|
|
|
Site Admin |
|
Joined: Sun Aug 03, 2003
2:02 pm Posts: 451 Location: Erie, PA
|
Greetings kpainter:
Thanks for that great
list. Somebody did a lot of work scouting out all
those rules of thumb.
So, does anybody know
any others, or care to refute/modify any of the
ones on kpainter's list?
_________________ - Kirt Blattenberger
RF Cafe Progenitor & Webmaster
|
|
|
|
|
Ted Cline |
Post subject: Re: Rules of Thumb
Posted: Wed Feb 18, 2009 3:48 pm
|
|
|
Captain |
|
Joined: Fri Aug 26, 2005
8:25 am Posts: 6 |
Here's one I can offer. It's more of a tip than
rule of thumb. If you are using chip caps and notice
a larger than expected variation in values, it might
be due to the orientation of the chip cap on the
PCB. The parallel plates of the cap are all oriented
in one direction. If there is enought metal near
the cap, the fringe fields can be enough to affect
the performance. Careful PCB layout can usually
prevent it, but if you are seeing larger than expected
variations, check it out. Other than using
an x-ray, there is really no way to tell which way
the plates are oriented internally because most
RF cap packages are square. If you have time to
play around, try experimenting with this. If I had
more time, I'd do a study myself. For that matter,
there probably already is one somewhere.
I guess I'm just lazy.
|
|
|
|
|
IR |
Post subject: Re: Rules of Thumb
Posted: Fri May 22, 2009 4:26 pm
|
|
|
Site Admin |
|
Joined: Mon Jun 27, 2005
2:02 pm Posts: 392 Location: Germany
|
Here is one of mine. IP3 measurement is
considered valid for small signal conditions. Small
signal applies as long as the difference between
the fundamental product to the 3rd orer product
is equal or bigger than20dBc, i.e.: P3-P1≤-20dBc
Where: P3 - 3rd order product (dBm).
P1 - fundamental power (dBm). This rule
of thumb is according to the IEEE, so it has been
already checked out rigorously.
_________________ Best regards,
-
IR
|
|
Posted 11/12/2012
|
|
|