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.