[eagle] Re: Eagle Microwave Antenna Arrays -- mechanical concepts

Franklin Antonio antonio at qualcomm.com
Fri Mar 23 15:36:31 PST 2007


At 03:24 PM 3/23/2007, John B. Stephensen wrote:
>There are probably better phase shifters available. I just happened 
>to see these while looking at an MA/COM catalog. LNA MMICs have a 
>gain variation of about 3 dB and at least 1 dB of the variation is 
>probably temperature related, so the phase shifter loss doesn't need 
>to be controlled too precisely.

A related thought... My first thought was that the programmable 
attenuator was an absurd complexity.  I was reacting to the thought 
that it was just there to fix this stupid feature of the phase 
shifter.  However, there will be other things that make the levels 
slightly different at each antenna.  Losses, splitter imbalances, god 
knows what.  A programmable attenuator per element could shim all 
these things.  Once per cycle, the software would just write a few 
bits to each antenna element, some of the bits going to the digital 
phaseshift chip, and some going to the digital attenuator 
chip.  Maybe the attenuator is a good thing.

Still... 3dB !!!  Such a big phase shifter loss VARIATION with phase 
is something we'd want to compensate for no matter what the LNA gain 
variation with temperature or whatever was.



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