falcon.16 wrote:With Pesa radars the noise figure its around 4-6 db if this picture is correct.

I have a question, if noise figure is 4-6 db, does it mean radar need receive from target more than 4-6 db for get detection?
I think 4-6 db is around 4-5 m2...so any fighter less than 4 m2 RCS would be not detect...ummm, i am very confused about it.
Yes, that's true that in PESA radars the noise figure is significantly higher than in AESA radars. This is because there are more lossy elements in the signal path. This means that in PESA radar the received signal needs to be significantly stronger than in AESA radar to overcome the internal noise.
Decibel is just a ratio (dimensionless unit) and you are thinkin about dBm which is decibel-milliwatts which has reference to milliwatt (a unit). In the picture PESA has noise figure of 3.05 - 0.25 dB = 2.8 dB. This means the received signal from target needs to be almost 2 times higher in PESA than in AESA to be detected. That alone gives AESA almost 20 percent longer range.
One has to remember that the same losses also affect transmit path and the actually transmitted radar signal power is quite a bit lower in PESA than in AESA radar if the power generated by the transmitters is the same. The loss is pretty much the same in transmit path as in receive path meaning that with same transmitter power the AESA will have about 40 percent longer range when both transmit and receive paths are considered.
And that's not all. AESA antennas tend to have higher gain than PESA antennas which means the antenna is more efficient to transmit and collect radar signals. This further improves range and other qualities. Of course current AESA radars can also transmit at higher power levels than best PESA radars and in the future the difference will only get bigger.