Originally Posted by JFZ90
In general, the radar aperture (antenna area) doubles with a 1.41 times increase in diameter. With all else being constant it takes an increase in aperture of 10x to double the range of a radar. Technologies like AESA antennas increase the output and sensitivity of a radar for any given size. Advanced T/R module technology and smaller T/R modules also do that. PESAs generally reduce sensitivity. Both types of ESAs allow instantaneous beam steering and high beam focus. Only the AESA can form multiple beams simultaneously. .
Errrr.... for clarity.
Radar range (in the physics sense) is driven by the total power output of the transmitter, the reflectivity of the target, and the sensitivity of the receiver - not by the antenna aperture. It varies with the fourth power of Tx energy (power squared for the outbound journey, power squared for the return journey); if you want to double the range of a radar, you don't double the antenna size, you up the power output by sixteen. The antenna size is more relevant for main beam width. That and your PRF schedule and pulse-to-pulse detection probabilities drive your scan rate, which drives... a lot of other design decisions.
Google "radar range equation".
Aperture size only becomes relevant if you're talking about the Tx energy being made up of lots of active array elements which each have a maximum power output - the AESA total Tx energy varies with the aperture size only if you assume identical Tx/Rx modules. All else being equal, the 16x increase in the number of elements required to double your AESA range comes from a x4 radius increase. Of course, an upgrade to the power output of each Tx/Rx module can achieve exactly the same thing - and such improvements keep coming along. Or, you could use a swashplate design, and add more T/R elements for the same frontal diameter.
Another thought is that it isn't as simple as "total power per element times number of elements" - not all of the elements will transmit at full power all of the time, for various reasons.
I'm not sure how Moore's law affects T/R elements, but I suspect that it's a fast-evolving area (google "graphene" for the latest fun). You may find that a smaller, newer AESA ends up with better performance than a larger, older one.