The EVM failure caused by the interference between MIMO Tx trace

[timer000]

I have been reading some documents about 5G IC manufacturers recently.
I found a problem It mentions that one PA output of a MIMO system will interfere with another MIMO antenna’s PA input and PA output This will reduce the EVM To solve this problem,
the manufacturer requires that each PA in the system be covered with a different Shielding case.
and set a very strict isolation requirements between:
1.The isolation of PA output to another PA input
2,The isolation of PA input to another PA input/output

According to my previous understanding:

1.PA’s TX will interfere with RX, reducing its sensitivity.
2.PA’s TX path may couple to RX path and affect the IC’s VCO, reducing TX’s EVM.
3.PA input is not tuned to 50ohm, which will also cause TX S11 to bounce back, reducing TX’s EVM

I thought that TX would not be affected by another PA because the signal was strong enough.
But I didn’t expect that MIMO PA output can also interfere with another PA input and output.

So I want to ask two questions:

1.Is this phenomenon because MIMO PAs work on the same or close frequency? So TX will interfere with each other?
2.Does this interference affect the EVM of another PA because of VCO pulling?

I am a RF novice, is it possible that some experts could give me some directions. Thank you.

 

[dick_freebird]

Well, they probably are at least all within the same band and incoming,
you have zero control over frequency or phase. So best keep them
separated.

RF CMOS switches are a big deal here, amp in a can is all swell but
the inputs and outputs have to go somewhere. Super wide SP_T
switches are made for MIMO.

But I ain't your expert.