Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would
be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate
that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views.
It seems that the more formal social media like Facebook pretty much dominate this kind of venue anymore anyway, so if
you would like to post something on RF Cafe's
page, please do.
Below are all of the forum threads, including all
the responses to the original posts.
Post subject: Noise figure increase
Posted: Wed Dec 09, 2009 6:40 am
Joined: Wed Jun 04, 2008 3:23 am
I am trying to design a 30 dB Low noise amplifier at 9.5 GHz using the FHX13X super low noise HEMT from fujitsu as the first stage. I am able to meet all the specs but I have encountered a weird phenomenon. During the noise figure measurement for a certain percentage of modules the noise figure starts low (around the designed spec of 1.2 dB) and goes on to slowly increase with time to 2.5 dB. For every measurement cycle (of the noise figure analayzer) it seems to increase 0.02 dB. What are the possible reasons for this?
Post subject: Re: Noise figure increase
Posted: Fri Dec 18, 2009 12:13 pm
Joined: Mon Sep 01, 2003 6:59 pm
Are these packaged LNA, or open substrate? The increasing NF over time suggests either a charge accumulating (possibly bias capacitance), or a temperature realted issue. Both could be caused by poor solder joints. Have you already ruled out these two possibilities?