RF Cascade Workbook for Excel
RF & Electronics Symbols for Visio
RF & Electronics Symbols for Office
RF & Electronics Stencils for Visio
RF Workbench
T-Shirts, Mugs, Cups, Ball Caps, Mouse Pads
Espresso Engineering Workbook™
Smith Chart™ for Excel
|
 |
Adding two RF signals!!! - RF Cafe Forums
|
jefkat
Post subject: Adding two RF signals!!!
Unread postPosted:
Wed Jun 01, 2005 6:03 am
Offline
Lieutenant
Joined: Wed
Jun 01, 2005 5:57 am
Posts: 2
Heey !
I have two antiphase
Rf signals at 900MHz (not sinusoidal)...I wanna add them up. By doing
this actually I intend to cacel out the odd harmonics and add up even
ones.......
Any suggestions out there !!!
have fun bye!
jefkat
Top
Profile
Guest
Post subject:
Unread postPosted:
Wed Jun 01, 2005 11:46 am
From the description of the method
you suggest, you are not looking for a signal sumation but for some
sort of harmonic cancelation.
Because would it be a summation
the phase relationship of all harmonic would be the same.
Right?
Top
Guest
Post subject:
Unread postPosted:
Thu Jun 02, 2005 3:19 am
Thanks for the comments..
yeah that's
right..........what I want is a second harmonic, If I can.....
one
way is to do something like this. (with capacitors)...but this divides
the amplitude as well....
In + In-
\ /
= =
\ /
\/______
Out
|
=
|
Gnd
greoten!
Top
Guest
Post subject: Adding two RF signals
Unread postPosted:
Wed Jun 08, 2005 11:39 am
Unfortunately, you can't use passive
circuits to add voltages without loss.
You can only passively
add power in watts: 1Watt + 2 Watts <= 3 Watts for any kind of passive
combiner.
Otherwise, adding 1V to 2v would give 3V, which gives
more power out than in: power for free - unless the signals aren't matched
impedance to begin with. And you don't get power for free.
Good
Luck!
Top
CK
Post subject:
Unread postPosted:
Thu Jun 09, 2005 4:58 pm
I think you would want to actively
add the two signals. If they were at a low frequency, you would use
an op-amp, carefully adjust the input level of each signal to be the
same, and adjust the phase of one signal so the fundamental cancels
in out.
At RF, you might try to use a Gilbert cell active mixer
such as the Intersil HFA3101 or some other one with sufficient frequency
range.
Top
cubeleg
Post subject: Why not
use OP?
Unread postPosted: Mon Jul 18, 2005 12:40 pm
Why
you cannot use an op. amp. with a high bandwith? for example AD800¿1?
(I'm not sure) has 1GHz of bandwidth. Probably this a stupid question,
but I'm new in the RF.
Top
Guest
Post subject:
Response to Cubeleg
Unread postPosted: Mon Jul 18, 2005 6:51 pm
When an opamp is rated at 1 GHz, the number is for the gain-bandwidth
product. An amplifier with a gain of 1 isn't particularly useful - a
1 GHz GBW opamp is really only starting to be useful as you go below
100 MHz.
Good luck!
Posted
11/12/2012
|
|
|
|
|
