Preamplifier design : Input and Load reflection coefficient

[sthim]

The preamplifier that I can trying to design is suppose to have a
constant vswr that is suppose to be within certain nf limits. If I
manage to figure out a load reflection coefficient value that would
make the vswr fall with the required nf circle, that I will be able to
design the matching networks. However, I am unable to do that. At
that moment, I have managed to find the vswr circle using the input
reflcetion coefficient relation. I would need to find the load
reflection coefficient using this parameter and I am not sure how to
do that. Or I may be approaching this problem in an incorrect way.

sthim2003

 

[Rene Tschaggelar]

sthim wrote:

The preamplifier that I can trying to design is suppose to have a
constant vswr that is suppose to be within certain nf limits. If I
manage to figure out a load reflection coefficient value that would
make the vswr fall with the required nf circle, that I will be able to
design the matching networks. However, I am unable to do that. At
that moment, I have managed to find the vswr circle using the input
reflcetion coefficient relation. I would need to find the load
reflection coefficient using this parameter and I am not sure how to
do that. Or I may be approaching this problem in an incorrect way.

Are you simulating the design or are you building it.
In case of the later you need to measure the stuff.

Input and output reflections are independent of each other,
at least from a certain complexity up. That is the point of an
amplifier, to decouple input from output.

Rene
--
Ing.Buero R.Tschaggelar - http://www.ibrtses.com
& commercial newsgroups - http://www.talkto.net

 

[Active8]

On 18 Jan 2004 17:20:46 -0800, sthim2003@yahoo.com said...

The preamplifier that I can trying to design is suppose to have a
constant vswr that is suppose to be within certain nf limits. If I
manage to figure out a load reflection coefficient value that would
make the vswr fall with the required nf circle, that I will be able to
design the matching networks. However, I am unable to do that. At
that moment, I have managed to find the vswr circle using the input
reflcetion coefficient relation. I would need to find the load
reflection coefficient using this parameter and I am not sure how to
do that. Or I may be approaching this problem in an incorrect way.

sthim2003

Try searching google for an app note from Motorola or HP on Small

Signal Amplifier Design Linvill Method or some combination of those
words.

What transistor is it? Doesn't the spec sheet give a bias point and
input reflection coefficient (not a vswr circle) for optimum NF?
--
Best Regards,
Mike

 

[Precious Pup]

Rene Tschaggelar wrote:

Input and output reflections are independent of each other,...

S12 is never 0. Design equations for simultaneous I/0 match are available.

 

[sthim]

I am only simulating it at the moment. I am going to use a Agilent
ATF series PHEMT.

sthim2003


Active8 <mTHISREMOVEcolasono@earthlink.net,invalid> wrote in message news:<MPG.1a758794de156a9b9898ab@news.west.earthlink.net>...

On 18 Jan 2004 17:20:46 -0800, sthim2003@yahoo.com said...
The preamplifier that I can trying to design is suppose to have a
constant vswr that is suppose to be within certain nf limits. If I
manage to figure out a load reflection coefficient value that would
make the vswr fall with the required nf circle, that I will be able to
design the matching networks. However, I am unable to do that. At
that moment, I have managed to find the vswr circle using the input
reflcetion coefficient relation. I would need to find the load
reflection coefficient using this parameter and I am not sure how to
do that. Or I may be approaching this problem in an incorrect way.

sthim2003

Try searching google for an app note from Motorola or HP on Small
Signal Amplifier Design Linvill Method or some combination of those
words.

What transistor is it? Doesn't the spec sheet give a bias point and
input reflection coefficient (not a vswr circle) for optimum NF?