how do i build a guard ring
Yup, As per K_90 it's the layout engineer duty to balance the cost, yield and working.
Adding to K_90 concept I want to add some more in regards of noise seperation b/w blocks.
If your technology/project allows you to use triple well process, I suggest to use the Deep_Nwell layer for complete isolation.
If we dicuss about guardring concept, What actually guarding is doing.
When ever we are forming a guardring, we are giving a negative supply to that.
i.e For Nwell guardring AVDD and P-Guardring AVSS. It means we are making that one reverse bias and forming a barrier b/w two blocks.
So as per K_90's stream and river example it's always prefred to use more widths for better noise isolation. But remember If you are increasing widhts also you are making a barrier from sidewalls only. If you see it from cross-sectional view you will get it . Still you are not completely isolating your block with noise one. Because your noise coming from substrate deeps. This is concept for N-mos devices only.
To do complete isolation, In some of my previous projects I used DEEP_NWELL as burried layer. It's possible when our technology/project allows us only.
If any doubts regarding Burried layer...Welcome. I can give you some ans...!!!