The vast number of different tactical radar systems and their applications can be overwhelming. However, most tactical systems rely on one of two main technologies — passive or active electronically-scanned arrays. Before investigating the advantages and disadvantages of PESA radar vs. AESA radar, let’s discuss the basics of how radar sensors work.
What is a Radar?
A radar, short for radio detection and ranging, is a communications technology that uses radio waves to locate and identify objects. It was originally developed and used by ship captains to communicate with their radio towers. They realized that objects in between the towers and the ship caused interference and made them unable to communicate.
What started as an inconvenience quickly turned into a new strategy for defense — not only in the water, but on land and in the sky.
How Do Radars Work?
Simply put, a radar works by sending out radio waves and waiting for a response back, much like an echo. The amount of time it takes for the waves to return indicates how far away the object is. Additionally, sending waves out from various points, helps to better determine the location of the object.
In their most basic forms, radar systems consist of an antenna, a radio transmitter and an object for signals to bounce off of. The antenna communicates with a receiver, which amplifies echoes that bounce off the objects the signals hit and display them to the user in a meaningful, typically visual way.
The Problem With Traditional Radars
One of the most obvious problems with this rudimentary form of radars is that the antenna must be physically moved to locate signal responses in different directions or areas. In the 1960s, engineers took the first step in solving this problem by developing the first phased array antenna as part of a passive electronically scanned array (PESA) radar system.
What Are Phased Array Antennas?
Unlike the original model for radar systems which featured a single antenna, phased array systems rely on a grid of antennas to transmit and receive signals.
With the old system of one large antenna, it was difficult to focus and direct the signal being put out. Rather than transmitting in one direction, the signal would output in all directions, like the ripple of a drop of water. This means it would not only bounce off of threats, but it would also bring back locations of nearby buildings, landscape features and non-threatening vehicles.
By building an array of smaller antennas, the beams interfere with one another, constructing a broad beam, but also intersecting into a much narrower beam. By looking only at the results of this narrow intersection, extraneous information being brought back can be filtered out and eliminated.
Furthermore, by adding a delay to some of the signals, the beam’s direction can be controlled quickly and precisely by altering the location of the intersection of the beams.
A PESA radar takes one signal at a single frequency and splits it between different strategically placed antennas to maximize its range and strength.
Not only do we receive the normal information from the signal response, but we can also learn a great deal about the distance and position of the object based on the interference of the strategically-placed antennas and the way they interrelate.
PESA Radar Advantages
One of the most significant advantages of a PESA radar system is that the delay of certain signals can be controlled completely electronically, meaning that the signal can be steered quickly and precisely without moving any of the antennas. PESA radar systems are valuable because they can scan large areas much faster than traditional mechanical radar systems.
PESA Radar Disadvantages
While the PESA radar was groundbreaking in terms of speed and area, it has significant disadvantages. What it makes up for in range, it loses in accuracy, as the beams of radio waves it puts out are broad and cannot give the most precise location information back.
The PESA radar is also limited by its range capability and the fact that it has only one beam, which means it can send out only one frequency at a time. In addition, it has only one transmitter, so there is potential for system failure due to a single failure within the transmitter.
Size can also be a disadvantage, as PESA radar sensors are typically very large and heavy. They can also be prone to cooling problems since so much information is running through a central point.
As technology advanced and receivers and transmitters could be made much lighter and smaller, active electronically scanned array (AESA) radar systems were invented.
Rather than having one central transmitter, each antenna has its own solid-state transmit receive module or TRM. These modules are controlled by computers that function as both transmitters and receivers.
AESA Radar Advantages
With AESA radar technology, radio waves can be sent out at different frequencies in multiple directions at the same time without moving any antennas. While PESA radar systems may be able to scan larger sections faster, AESA scans more precisely. In addition, by scanning at different frequencies, it brings back more valuable information to its user.
The benefits of AESA radar include:
- Longer range
- Ability to detect smaller targets
- Better resistance to jamming
Since an AESA radar utilizes a broader set of frequencies, it is also much more difficult to detect among background radio noise. This helps vehicles remain undetected while defending themselves in their environments.
Finally, AESA radars are less likely to experience system failure, since they rely on not one, but dozens of TRMs to transmit their signals. Computer failure can be recognized and remedied much faster than the maintenance needed to fix a broken transmitter in a PESA system. Additionally, the functioning antennas in an AESA system can continue to operate while the single TRM or computer is fixed.
AESA Radar Disadvantages
The AESA radar is generally considered the most innovative and technologically-advanced type of tactical radar system. That being said, it does have one notable disadvantage — its limited field of view (FOV).
Currently, the maximum FOV for a standard flat phased AESA antenna is between 90 and 120 degrees. But, by combining mechanical movement with the system, the limited AESA radar range can be vastly increased.
What Is the Difference Between AESA and PESA Radars?
The major difference between an AESA and PESA radar is the number of transmitters. A PESA system relies on one large transmitter, while AESA systems have multiple TRMs. This allows for greater reliability, smaller size and weight, and a lower threat of being detected due to the use of multiple frequencies. While both systems are still used in the military, the relevant differences between a PESA radar vs. an AESA radar will likely depend on the use case and application.