^^ The bold part is what you wrote...
No part moves in PESA and AESA RADARs..
PESA RADAR
A passive electronically scanned array (PESA), contrary to its active counterpart AESA, is a phased array which has a central radiofrequency source (such as a magnetron, a klystron or a travelling wave tube), sending energy into (usually digitally-controlled) phase shift modules, which then send energy into the various emitting elements in the front of the antenna. AESA devices, in contrast, have each of their elements contain its own radiofrequency source. A PESA radar is therefore simpler to construct than an AESA.
Most phased array radars in the world are PESA. Microwave Landing System uses PESA transmit-only arrays.
In wave theory, a phased array is a group of antennas in which the relative phases of the respective signals feeding the antennas are varied in such a way that the effective radiation pattern of the array is reinforced in a desired direction and suppressed in undesired directions.[1] Phased array transmission was originally developed in 1905 by Nobel Laureate Karl Ferdinand Braun who demonstrated enhanced transmission of radio waves in one direction.[2] During World War II, Nobel Laureate Luis Alvarez used phased array transmission in a rapidly-steerable radar system for "ground-controlled approach", a system to aid in the landing of airplanes in England. At the same time GEMA in Germany built the PESA Mammut 1.[3] It was later adapted for radio astronomy leading to Nobel Prizes for Physics for Antony Hewish and Martin Ryle after several large phased arrays were developed at the University of Cambridge. The design is also used in radar, and is generalized in interferometric radio antennas. DARPA researchers recently announced a 16 element phased array integrated with all necessary circuits to send at 30–50 GHz on a single silicon chip for military purposes
Phased array - Wikipedia, the free encyclopedia
Active Electronically Scanned Array
An Active Electronically Scanned Array (AESA), also known as active phased array radar is a type of phased array radar whose transmitter and receiver functions are composed of numerous small solid-state transmit/receive modules (TRMs). AESAs aim their "beam" by broadcasting a number of different frequencies of coherent radio energy that interfere constructively at certain angles in front of the antenna. They improve on the older passive electronically scanned radars by spreading their broadcasts out across a band of frequencies, which makes it very difficult to detect over background noise. AESAs allow ships and aircraft to broadcast powerful radar signals while still remaining stealthy.
.............................
The primary advantage of a AESA over a PESA is that the different modules can operate on different frequencies. Unlike the PESA, where the signal was generated at single frequencies by a small number of transmitters, in the AESA each module broadcasts its own independent signal. This allows the AESA to produce numerous "sub-beams" and actively "paint" a much larger number of targets. Additionally, the solid-state transmitters are able to broadcast effectively at a much wider range of frequencies, giving AESAs the ability to change their operating frequency with every pulse sent out. AESAs can also produce beams that consist of many different frequencies at once, using post-processing of the combined signal from a number of TRMs to re-create a display as if there was a single powerful beam being sent.
http://en.wikipedia.org/wiki/Active_electronically_scanned_array
