Noise figure increase - RF Cafe Forums

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shireesha
 Post subject: Noise figure increase
Posted: Wed Dec 09, 2009 6:40 am 
 
Captain

Joined: Wed Jun 04, 2008 3:23 am

Posts: 11

Hello,

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?

Thanks.
 
   
 
maxwell
 Post subject: Re: Noise figure increase
Posted: Fri Dec 18, 2009 12:13 pm 
 
Captain
 

Joined: Mon Sep 01, 2003 6:59 pm

Posts: 13

Location: Boston

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?

Posted  11/12/2012