Post subject: Best solution for RF protection Posted: Sun
Jan 11, 2009 10:13 pm
Joined: Fri Jan
26, 2007 2:40 am
I've got a specification that
allows as much as +20 dBm into a receive input but many LNAs can't
take that much power without ruining the amplifier. Is there some
kind of diode circuit that can be used for protection against such
a RF input without creating distortion at a reasonably lower level?
My input is relatively low frequency (1-30 MHz...HF).
Post subject: Posted:
Fri Jan 23, 2009 3:18 am
Jan 26, 2007 2:40 am
Anyone have any ideas?
Posted: Fri Jan 23, 2009 12:47 pm
Fri Feb 17, 2006 12:07 pm
Location: London UK
There are one or two bits of data missing before I can get my
addled head around this one.
Is the frequency of the +20dBm
signal very close to weaker signals you are trying to detect/decode?
And is it at a fixed frequency or anywhere in the range?
the +20dBm signal pulsed or continuous?
Are the weaker signals
spread over a random spectrum from 1-30MHz?
I would certainly
look around for bomb-proof front-end amplifiers, such as the approach
using transmit transistors with a measured and adequately low noise
factor as the first stage. This approach has been shown to yield
very high IP3 figures.
At bottom, life
is all about
Sucking in and blowing out.
Post subject: Posted: Mon Jan 26, 2009 5:58 pm
Joined: Fri Jan 26, 2007 2:40 am
The frequency is anywhere in the 1-30 MHz range. This is
NOT a performance spec so much as it is a "damage" spec. Another
words we don't have to receive anything in particular while this
is going on.
I think the damage spec is "continuous".
The one thing that is tough here is that most gain block
amps I see have absolute max inputs no more than +18 dBm (most MiniCircuits
amps have +13 dBm). It's hard enough just finding an amp that will
work in this range anymore (due to most focus on the higher ranges)
let alone an absolute max this high. Therefore some sort of circuitry