So a number of the tech options say they incerease whatever by some %, so my question is say you a sheild with 100 strength, you reasearch the next sheild level, you get 110 strenght, so then on the next level, do you get 120 strenghth or 100 * 1.2, or do you get 121 or (100*1.1)*1.1

It is 10% of the base amount. So a shield of 100 strength would gain an additional 10 strength for each shield level upgrade.

-Istalris-

I understand that much, but my question is what happenes when you get to lvl 2 and above

Shield = [Base Shield] + ([Shield Tech lvl] x 10%) x [Base Shield]

Multiply your shield tech lvl by 10% that's the additional percentage to your base shield.
Simply

Istalris wrote:It is 10% of the base amount. So a shield of 100 strength would gain an additional 10 strength for each shield level upgrade.

Lvl 2 = 120
Lvl 3 = 130

So upgrading from lvl 1 to 2 will give you an additional 20% of the base amount.
Not an additional 10% to the current amount.