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I need your comments diversity antenna distribution system for UHF broadband

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coolpixs4

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I have designed a diversity antenna distribution system for UHF broadband

My first design as Case 1 (attached picture)
Port 1 is comming from Antenna 1
Port 2 is comming from Antenna 2

It is a diversity antenna distributor system to multiple receivers.
If port 1 is fed by 10dBm RF signal the isolated P1-P2 is about 30 dB

The situation are:
- Firstly, the LNA is used is Berex BL022 (I though this LNA has its own prolem that's why The Berex now discontinued this IC and then release a new one with the new name BL022A)
- Previously, If port 1 is fed and port 2 is open then one of the IC become damaged (when using BL022) => The new team leader said due to the isolated between P1/P2 (case 1), so the signal from LNA1 going to output of the LNA2 (if port 2 open) then accumulated reflect => damaged. Is it true ?

- The same circuit in Case 1, after I changed the IC to BL022A, and did not observe any damaged

Now, the new team leader who comming this year in our team, he asked me to modiffy the circuit to the Case 2 (attached picture)
- Removed LNA 1, LNA 2 and using only a single LNA as depicted in Case 2 (this is a temporary modding for test)
- Case 2, The isolated property from P1-P2 drop to about 13dB

In my opinion, if we modify the circuit as Case 2, we will loosing the diversity of the two antenna.

Please, give me any comments or advice.
Which one is correct Case 1 or Case 2 ?

Thank you.
 

Something doesn't make sense. The maximum rating for maximum input power of BL022 is +24dBm (damage input power).
Ignoring all the losses, the isolation and couplings on the PCB, you mentioned that you feed the board (at one of the ports) with +10dBm and the BL022 get damaged.
How can this happen? Do you feed somewhere else the board with higher RF power? Or BL022 died due to higher Vcc voltage, accidentally set.
 

I also don't know why ? and what are the reasons?, but a lot of our products on sale already get A/S because of damaged LNA.
And I also have a wonder that the BL022 itself has some problem; that's why Berex company discontinued this IC and release a new name BL022A with same spec's.
 

=> The new team leader said due to the isolated between P1/P2 (case 1), so the signal from LNA1 going to output of the LNA2 (if port 2 open) then accumulated reflect => damaged. Is it true ?

Makes no sense to me

Now, the new team leader who comming this year in our team, he asked me to modiffy the circuit to the Case 2 (attached picture)

That adds a lot of signal path loss (3dB from coupler etc) in front of the LNA, which means the noise figure goes up. I think your design with the separate LNAs first is much smarter if noise figure matters.
 

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