The j-20 should always have the Luneberg lens open, which means that the e-3 can't find the j-20 with the Luneberg len open in time?
E-3 insufficient for timely detection of J-20: Pacific Air Forces chief...
E-3 insufficient for timely detection of J-20: Pacific Air Forces chief
https://www.flightglobal.com/defence/e-3-insufficient-for-timely-detection-of-j-20-pacific-air-forces-chief/147939.article
There is no evidence that klj-7a used GAN.
According to the interviewed with the designer at the Zhuhai Air Show, the detection distance of the klj-7a to the RCS=5 target is 170km.
According to this link
https://www.aviationtoday.com/2009/06/01/serious-squall/
the early estimate of RBE-2 AESA...