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R: Input impedance of DEMI2400-144RX?



Hi  Scott,

If the input device of DEMI2400-144RX is a GaAsFET and if the input network
has been adjusted for the lowest Noise Figure to 50 ohm input,than the
reflection coefficient S11 allow you to get at best a return loss of  3 to 4
dB or an input VSWR very high around 5 or 6.

Such high input VSWR is normal in a devices such a GaAsFET adjusted for the
lowest Noise Figure.

If you look at the scattering parameters of a GaAsFET for minimum noise ad
make an exercise using PUFF,Computer Aided Design for Microwave Integrated
Circuits Version 2.0 you will get the answere to your question.

PUFF is widely used in Europe and originated as a teaching tool for
Caltech's microwave circuits course by professors:

Scott W. Wedge
Richard Compton
David Rutledge

PUFF Distribution
Electrical Engineering M/S 116-81
California Institute of  Technology
Pasadena, CA 91125

FAX to (818) 356-2137

73 de i8CVS Domenico


----- Original Message -----
From: Scott Townley <nx7u@arrl.net>
To: <amsat-bb@AMSAT.Org>
Sent: Monday, July 23, 2001 1:37 AM
Subject: [amsat-bb] Input impedance of DEMI2400-144RX?


> Has anyone measured the input impedance/VSWR of the DEMI 2400-144RX
> downconverter?
> Trying to assess whether mine is nominal or not.
> So far have measured 20dB conversion gain but input VSWR is very high,
> which may mean nothing depending on the design philosophy.
> TIA,
> Scott Townley
> nx7u@arrl.net
> ----
> Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
> To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
>








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