RADAR or Radio Detection and Ranging is a primary threat detection and guidance system of any armed forces for safeguarding the airspace as well as for sea surface area. Radar basically transmits radio waves or microwaves and when the waves hit a body like an aircraft, missile or a ship and comes back after reflection, the receiver receives it and gets the position of the body.
There are several types of radars available as well as new technologies are coming everyday. AESA radar is one of the most used radar today. To understand AESA radar we have to first understand what is PESA radar ? PESA or Passive Electronically Scanned Array or phased array system consists of several transmitter and receivers acting as a single system. For a single transmitter receiver system radar the antenna needs to be mechanically rotated in the direction for scanning, which is not an easy job as well as it faces maintenance issues.
Then the concept of phased array system came. In a phased array system, the waves can be directed without changing the antenna direction. Several transmitters and receivers are placed in it, which simultaneously transmits and receives signals. Using the property of interference during superpostion of waves, the antenna transmits waves in several directions without rotating as shown in the animation. This is known as phased array system or commmonly known as PESA radar.
Phased array radar system. Courtesy: Wikipedia
AESA radars or Active Electronically Scanned Array radars are upgraded version of PESA radars. The main difference is PESA radars only operate in a single frequency only, whereas AESA radars transmits radio waves of a wide range of frequencies simultaneously. This makes the radar more protected against jammers; if jammers jam one frequency, AESA radar can work with other available frequencies. There are several AESA radars available in market. In India DRDO has developed a radar called Uttam AESA radar for aircrafts which is in its testing phase and will be integrated in TEJAS, TEDBF and AMCA later.
Data Sources: https://youtube.com https://en.wikipedia.org/wiki/Active_electronically_scanned_array